doc/webserver/user-manual/actions-file.html

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  36             Privoxy 3.0.18 User Manual
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  53       <h1 class="SECT1">
  54         <a name="ACTIONS-FILE">8. Actions Files</a>
  55       </h1>
  56       <p>
  57         The actions files are used to define what <span class="emphasis"><i
  58         class="EMPHASIS">actions</i></span> <span class=
  59         "APPLICATION">Privoxy</span> takes for which URLs, and thus
  60         determines how ad images, cookies and various other aspects of HTTP
  61         content and transactions are handled, and on which sites (or even
  62         parts thereof). There are a number of such actions, with a wide range
  63         of functionality. Each action does something a little different.
  64         These actions give us a veritable arsenal of tools with which to
  65         exert our control, preferences and independence. Actions can be
  66         combined so that their effects are aggregated when applied against a
  67         given set of URLs.
  68       </p>
  69       <p>
  70         There are three action files included with <span class=
  71         "APPLICATION">Privoxy</span> with differing purposes:
  72       </p>
  73       <p>
  74       </p>
  75       <ul>
  76         <li>
  77           <p>
  78             <tt class="FILENAME">match-all.action</tt> - is used to define
  79             which <span class="QUOTE">"actions"</span> relating to
  80             banner-blocking, images, pop-ups, content modification, cookie
  81             handling etc should be applied by default. It should be the first
  82             actions file loaded
  83           </p>
  84         </li>
  85         <li>
  86           <p>
  87             <tt class="FILENAME">default.action</tt> - defines many
  88             exceptions (both positive and negative) from the default set of
  89             actions that's configured in <tt class=
  90             "FILENAME">match-all.action</tt>. It is a set of rules that
  91             should work reasonably well as-is for most users. This file is
  92             only supposed to be edited by the developers. It should be the
  93             second actions file loaded.
  94           </p>
  95         </li>
  96         <li>
  97           <p>
  98             <tt class="FILENAME">user.action</tt> - is intended to be for
  99             local site preferences and exceptions. As an example, if your ISP
 100             or your bank has specific requirements, and need special
 101             handling, this kind of thing should go here. This file will not
 102             be upgraded.
 103           </p>
 104         </li>
 105         <li>
 106           <p>
 107             <span class="GUIBUTTON">Edit</span> <span class="GUIBUTTON">Set
 108             to Cautious</span> <span class="GUIBUTTON">Set to Medium</span>
 109             <span class="GUIBUTTON">Set to Advanced</span>
 110           </p>
 111           <p>
 112             These have increasing levels of aggressiveness <span class=
 113             "emphasis"><i class="EMPHASIS">and have no influence on your
 114             browsing unless you select them explicitly in the
 115             editor</i></span>. A default installation should be pre-set to
 116             <tt class="LITERAL">Cautious</tt>. New users should try this for
 117             a while before adjusting the settings to more aggressive levels.
 118             The more aggressive the settings, then the more likelihood there
 119             is of problems such as sites not working as they should.
 120           </p>
 121           <p>
 122             The <span class="GUIBUTTON">Edit</span> button allows you to turn
 123             each action on/off individually for fine-tuning. The <span class=
 124             "GUIBUTTON">Cautious</span> button changes the actions list to
 125             low/safe settings which will activate ad blocking and a minimal
 126             set of <span class="APPLICATION">Privoxy</span>'s features, and
 127             subsequently there will be less of a chance for accidental
 128             problems. The <span class="GUIBUTTON">Medium</span> button sets
 129             the list to a medium level of other features and a low level set
 130             of privacy features. The <span class="GUIBUTTON">Advanced</span>
 131             button sets the list to a high level of ad blocking and medium
 132             level of privacy. See the chart below. The latter three buttons
 133             over-ride any changes via with the <span class=
 134             "GUIBUTTON">Edit</span> button. More fine-tuning can be done in
 135             the lower sections of this internal page.
 136           </p>
 137           <p>
 138             While the actions file editor allows to enable these settings in
 139             all actions files, they are only supposed to be enabled in the
 140             first one to make sure you don't unintentionally overrule earlier
 141             rules.
 142           </p>
 143           <p>
 144             The default profiles, and their associated actions, as
 145             pre-defined in <tt class="FILENAME">default.action</tt> are:
 146           </p>
 147           <p>
 148           </p>
 149           <div class="TABLE">
 150             <a name="AEN2625"></a>
 151             <p class="c2">
 152               Table 1. Default Configurations
 153             </p>
 154             <table border="1" frame="border" rules="all" class="CALSTABLE">
 155               <col width="1*" title="C1">
 156               <col width="1*" title="C2">
 157               <col width="1*" title="C3">
 158               <col width="1*" title="C4">
 159               <thead>
 160                 <tr>
 161                   <th>
 162                     Feature
 163                   </th>
 164                   <th>
 165                     Cautious
 166                   </th>
 167                   <th>
 168                     Medium
 169                   </th>
 170                   <th>
 171                     Advanced
 172                   </th>
 173                 </tr>
 174               </thead>
 175               <tbody>
 176                 <tr>
 177                   <td>
 178                     Ad-blocking Aggressiveness
 179                   </td>
 180                   <td>
 181                     medium
 182                   </td>
 183                   <td>
 184                     high
 185                   </td>
 186                   <td>
 187                     high
 188                   </td>
 189                 </tr>
 190                 <tr>
 191                   <td>
 192                     Ad-filtering by size
 193                   </td>
 194                   <td>
 195                     no
 196                   </td>
 197                   <td>
 198                     yes
 199                   </td>
 200                   <td>
 201                     yes
 202                   </td>
 203                 </tr>
 204                 <tr>
 205                   <td>
 206                     Ad-filtering by link
 207                   </td>
 208                   <td>
 209                     no
 210                   </td>
 211                   <td>
 212                     no
 213                   </td>
 214                   <td>
 215                     yes
 216                   </td>
 217                 </tr>
 218                 <tr>
 219                   <td>
 220                     Pop-up killing
 221                   </td>
 222                   <td>
 223                     blocks only
 224                   </td>
 225                   <td>
 226                     blocks only
 227                   </td>
 228                   <td>
 229                     blocks only
 230                   </td>
 231                 </tr>
 232                 <tr>
 233                   <td>
 234                     Privacy Features
 235                   </td>
 236                   <td>
 237                     low
 238                   </td>
 239                   <td>
 240                     medium
 241                   </td>
 242                   <td>
 243                     medium/high
 244                   </td>
 245                 </tr>
 246                 <tr>
 247                   <td>
 248                     Cookie handling
 249                   </td>
 250                   <td>
 251                     none
 252                   </td>
 253                   <td>
 254                     session-only
 255                   </td>
 256                   <td>
 257                     kill
 258                   </td>
 259                 </tr>
 260                 <tr>
 261                   <td>
 262                     Referer forging
 263                   </td>
 264                   <td>
 265                     no
 266                   </td>
 267                   <td>
 268                     yes
 269                   </td>
 270                   <td>
 271                     yes
 272                   </td>
 273                 </tr>
 274                 <tr>
 275                   <td>
 276                     GIF de-animation
 277                   </td>
 278                   <td>
 279                     no
 280                   </td>
 281                   <td>
 282                     yes
 283                   </td>
 284                   <td>
 285                     yes
 286                   </td>
 287                 </tr>
 288                 <tr>
 289                   <td>
 290                     Fast redirects
 291                   </td>
 292                   <td>
 293                     no
 294                   </td>
 295                   <td>
 296                     no
 297                   </td>
 298                   <td>
 299                     yes
 300                   </td>
 301                 </tr>
 302                 <tr>
 303                   <td>
 304                     HTML taming
 305                   </td>
 306                   <td>
 307                     no
 308                   </td>
 309                   <td>
 310                     no
 311                   </td>
 312                   <td>
 313                     yes
 314                   </td>
 315                 </tr>
 316                 <tr>
 317                   <td>
 318                     JavaScript taming
 319                   </td>
 320                   <td>
 321                     no
 322                   </td>
 323                   <td>
 324                     no
 325                   </td>
 326                   <td>
 327                     yes
 328                   </td>
 329                 </tr>
 330                 <tr>
 331                   <td>
 332                     Web-bug killing
 333                   </td>
 334                   <td>
 335                     no
 336                   </td>
 337                   <td>
 338                     yes
 339                   </td>
 340                   <td>
 341                     yes
 342                   </td>
 343                 </tr>
 344                 <tr>
 345                   <td>
 346                     Image tag reordering
 347                   </td>
 348                   <td>
 349                     no
 350                   </td>
 351                   <td>
 352                     yes
 353                   </td>
 354                   <td>
 355                     yes
 356                   </td>
 357                 </tr>
 358               </tbody>
 359             </table>
 360           </div>
 361         </li>
 362       </ul>
 363
 364       <p>
 365         The list of actions files to be used are defined in the main
 366         configuration file, and are processed in the order they are defined
 367         (e.g. <tt class="FILENAME">default.action</tt> is typically processed
 368         before <tt class="FILENAME">user.action</tt>). The content of these
 369         can all be viewed and edited from <a href=
 370         "http://config.privoxy.org/show-status" target=
 371         "_top">http://config.privoxy.org/show-status</a>. The over-riding
 372         principle when applying actions, is that the last action that matches
 373         a given URL wins. The broadest, most general rules go first (defined
 374         in <tt class="FILENAME">default.action</tt>), followed by any
 375         exceptions (typically also in <tt class=
 376         "FILENAME">default.action</tt>), which are then followed lastly by
 377         any local preferences (typically in <span class="emphasis"><i class=
 378         "EMPHASIS">user</i></span><tt class="FILENAME">.action</tt>).
 379         Generally, <tt class="FILENAME">user.action</tt> has the last word.
 380       </p>
 381       <p>
 382         An actions file typically has multiple sections. If you want to use
 383         <span class="QUOTE">"aliases"</span> in an actions file, you have to
 384         place the (optional) <a href="actions-file.html#ALIASES">alias
 385         section</a> at the top of that file. Then comes the default set of
 386         rules which will apply universally to all sites and pages (be <span
 387         class="emphasis"><i class="EMPHASIS">very careful</i></span> with
 388         using such a universal set in <tt class="FILENAME">user.action</tt>
 389         or any other actions file after <tt class=
 390         "FILENAME">default.action</tt>, because it will override the result
 391         from consulting any previous file). And then below that, exceptions
 392         to the defined universal policies. You can regard <tt class=
 393         "FILENAME">user.action</tt> as an appendix to <tt class=
 394         "FILENAME">default.action</tt>, with the advantage that it is a
 395         separate file, which makes preserving your personal settings across
 396         <span class="APPLICATION">Privoxy</span> upgrades easier.
 397       </p>
 398       <p>
 399         Actions can be used to block anything you want, including ads,
 400         banners, or just some obnoxious URL whose content you would rather
 401         not see. Cookies can be accepted or rejected, or accepted only during
 402         the current browser session (i.e. not written to disk), content can
 403         be modified, some JavaScripts tamed, user-tracking fooled, and much
 404         more. See below for a <a href="actions-file.html#ACTIONS">complete
 405         list of actions</a>.
 406       </p>
 407       <div class="SECT2">
 408         <h2 class="SECT2">
 409           <a name="AEN2724">8.1. Finding the Right Mix</a>
 410         </h2>
 411         <p>
 412           Note that some <a href="actions-file.html#ACTIONS">actions</a>,
 413           like cookie suppression or script disabling, may render some sites
 414           unusable that rely on these techniques to work properly. Finding
 415           the right mix of actions is not always easy and certainly a matter
 416           of personal taste. And, things can always change, requiring
 417           refinements in the configuration. In general, it can be said that
 418           the more <span class="QUOTE">"aggressive"</span> your default
 419           settings (in the top section of the actions file) are, the more
 420           exceptions for <span class="QUOTE">"trusted"</span> sites you will
 421           have to make later. If, for example, you want to crunch all cookies
 422           per default, you'll have to make exceptions from that rule for
 423           sites that you regularly use and that require cookies for actually
 424           useful purposes, like maybe your bank, favorite shop, or newspaper.
 425         </p>
 426         <p>
 427           We have tried to provide you with reasonable rules to start from in
 428           the distribution actions files. But there is no general rule of
 429           thumb on these things. There just are too many variables, and sites
 430           are constantly changing. Sooner or later you will want to change
 431           the rules (and read this chapter again :).
 432         </p>
 433       </div>
 434       <div class="SECT2">
 435         <h2 class="SECT2">
 436           <a name="AEN2731">8.2. How to Edit</a>
 437         </h2>
 438         <p>
 439           The easiest way to edit the actions files is with a browser by
 440           using our browser-based editor, which can be reached from <a href=
 441           "http://config.privoxy.org/show-status" target=
 442           "_top">http://config.privoxy.org/show-status</a>. Note: the config
 443           file option <a href=
 444           "config.html#ENABLE-EDIT-ACTIONS">enable-edit-actions</a> must be
 445           enabled for this to work. The editor allows both fine-grained
 446           control over every single feature on a per-URL basis, and easy
 447           choosing from wholesale sets of defaults like <span class=
 448           "QUOTE">"Cautious"</span>, <span class="QUOTE">"Medium"</span> or
 449           <span class="QUOTE">"Advanced"</span>. Warning: the <span class=
 450           "QUOTE">"Advanced"</span> setting is more aggressive, and will be
 451           more likely to cause problems for some sites. Experienced users
 452           only!
 453         </p>
 454         <p>
 455           If you prefer plain text editing to GUIs, you can of course also
 456           directly edit the the actions files with your favorite text editor.
 457           Look at <tt class="FILENAME">default.action</tt> which is richly
 458           commented with many good examples.
 459         </p>
 460       </div>
 461       <div class="SECT2">
 462         <h2 class="SECT2">
 463           <a name="ACTIONS-APPLY">8.3. How Actions are Applied to
 464           Requests</a>
 465         </h2>
 466         <p>
 467           Actions files are divided into sections. There are special
 468           sections, like the <span class="QUOTE">"<a href=
 469           "actions-file.html#ALIASES">alias</a>"</span> sections which will
 470           be discussed later. For now let's concentrate on regular sections:
 471           They have a heading line (often split up to multiple lines for
 472           readability) which consist of a list of actions, separated by
 473           whitespace and enclosed in curly braces. Below that, there is a
 474           list of URL and tag patterns, each on a separate line.
 475         </p>
 476         <p>
 477           To determine which actions apply to a request, the URL of the
 478           request is compared to all URL patterns in each <span class=
 479           "QUOTE">"action file"</span>. Every time it matches, the list of
 480           applicable actions for the request is incrementally updated, using
 481           the heading of the section in which the pattern is located. The
 482           same is done again for tags and tag patterns later on.
 483         </p>
 484         <p>
 485           If multiple applying sections set the same action differently, the
 486           last match wins. If not, the effects are aggregated. E.g. a URL
 487           might match a regular section with a heading line of <tt class=
 488           "LITERAL">{ +<a href=
 489           "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a> }</tt>,
 490           then later another one with just <tt class="LITERAL">{ +<a href=
 491           "actions-file.html#BLOCK">block</a> }</tt>, resulting in <span
 492           class="emphasis"><i class="EMPHASIS">both</i></span> actions to
 493           apply. And there may well be cases where you will want to combine
 494           actions together. Such a section then might look like:
 495         </p>
 496         <p>
 497         </p>
 498         <table border="0" bgcolor="#E0E0E0" width="100%">
 499           <tr>
 500             <td>
 501 <pre class="SCREEN">
 502   { +<tt class="LITERAL">handle-as-image</tt>  +<tt class=
 503 "LITERAL">block{Banner ads.}</tt> }
 504   # Block these as if they were images. Send no block page.
 505    banners.example.com
 506    media.example.com/.*banners
 507    .example.com/images/ads/
 508 </pre>
 509             </td>
 510           </tr>
 511         </table>
 512
 513         <p>
 514           You can trace this process for URL patterns and any given URL by
 515           visiting <a href="http://config.privoxy.org/show-url-info" target=
 516           "_top">http://config.privoxy.org/show-url-info</a>.
 517         </p>
 518         <p>
 519           Examples and more detail on this is provided in the Appendix, <a
 520           href="appendix.html#ACTIONSANAT">Troubleshooting: Anatomy of an
 521           Action</a> section.
 522         </p>
 523       </div>
 524       <div class="SECT2">
 525         <h2 class="SECT2">
 526           <a name="AF-PATTERNS">8.4. Patterns</a>
 527         </h2>
 528         <p>
 529           As mentioned, <span class="APPLICATION">Privoxy</span> uses <span
 530           class="QUOTE">"patterns"</span> to determine what <span class=
 531           "emphasis"><i class="EMPHASIS">actions</i></span> might apply to
 532           which sites and pages your browser attempts to access. These <span
 533           class="QUOTE">"patterns"</span> use wild card type <span class=
 534           "emphasis"><i class="EMPHASIS">pattern</i></span> matching to
 535           achieve a high degree of flexibility. This allows one expression to
 536           be expanded and potentially match against many similar patterns.
 537         </p>
 538         <p>
 539           Generally, an URL pattern has the form <tt class=
 540           "LITERAL">&lt;domain&gt;&lt;port&gt;/&lt;path&gt;</tt>, where the
 541           <tt class="LITERAL">&lt;domain&gt;</tt>, the <tt class=
 542           "LITERAL">&lt;port&gt;</tt> and the <tt class=
 543           "LITERAL">&lt;path&gt;</tt> are optional. (This is why the special
 544           <tt class="LITERAL">/</tt> pattern matches all URLs). Note that the
 545           protocol portion of the URL pattern (e.g. <tt class=
 546           "LITERAL">http://</tt>) should <span class="emphasis"><i class=
 547           "EMPHASIS">not</i></span> be included in the pattern. This is
 548           assumed already!
 549         </p>
 550         <p>
 551           The pattern matching syntax is different for the domain and path
 552           parts of the URL. The domain part uses a simple globbing type
 553           matching technique, while the path part uses more flexible <a href=
 554           "http://en.wikipedia.org/wiki/Regular_expressions" target=
 555           "_top"><span class="QUOTE">"Regular Expressions"</span></a> (POSIX
 556           1003.2).
 557         </p>
 558         <p>
 559           The port part of a pattern is a decimal port number preceded by a
 560           colon (<tt class="LITERAL">:</tt>). If the domain part contains a
 561           numerical IPv6 address, it has to be put into angle brackets (<tt
 562           class="LITERAL">&lt;</tt>, <tt class="LITERAL">&gt;</tt>).
 563         </p>
 564         <div class="VARIABLELIST">
 565           <dl>
 566             <dt>
 567               <tt class="LITERAL">www.example.com/</tt>
 568             </dt>
 569             <dd>
 570               <p>
 571                 is a domain-only pattern and will match any request to <tt
 572                 class="LITERAL">www.example.com</tt>, regardless of which
 573                 document on that server is requested. So ALL pages in this
 574                 domain would be covered by the scope of this action. Note
 575                 that a simple <tt class="LITERAL">example.com</tt> is
 576                 different and would NOT match.
 577               </p>
 578             </dd>
 579             <dt>
 580               <tt class="LITERAL">www.example.com</tt>
 581             </dt>
 582             <dd>
 583               <p>
 584                 means exactly the same. For domain-only patterns, the
 585                 trailing <tt class="LITERAL">/</tt> may be omitted.
 586               </p>
 587             </dd>
 588             <dt>
 589               <tt class="LITERAL">www.example.com/index.html</tt>
 590             </dt>
 591             <dd>
 592               <p>
 593                 matches all the documents on <tt class=
 594                 "LITERAL">www.example.com</tt> whose name starts with <tt
 595                 class="LITERAL">/index.html</tt>.
 596               </p>
 597             </dd>
 598             <dt>
 599               <tt class="LITERAL">www.example.com/index.html$</tt>
 600             </dt>
 601             <dd>
 602               <p>
 603                 matches only the single document <tt class=
 604                 "LITERAL">/index.html</tt> on <tt class=
 605                 "LITERAL">www.example.com</tt>.
 606               </p>
 607             </dd>
 608             <dt>
 609               <tt class="LITERAL">/index.html$</tt>
 610             </dt>
 611             <dd>
 612               <p>
 613                 matches the document <tt class="LITERAL">/index.html</tt>,
 614                 regardless of the domain, i.e. on <span class="emphasis"><i
 615                 class="EMPHASIS">any</i></span> web server anywhere.
 616               </p>
 617             </dd>
 618             <dt>
 619               <tt class="LITERAL">/</tt>
 620             </dt>
 621             <dd>
 622               <p>
 623                 Matches any URL because there's no requirement for either the
 624                 domain or the path to match anything.
 625               </p>
 626             </dd>
 627             <dt>
 628               <tt class="LITERAL">:8000/</tt>
 629             </dt>
 630             <dd>
 631               <p>
 632                 Matches any URL pointing to TCP port 8000.
 633               </p>
 634             </dd>
 635             <dt>
 636               <tt class="LITERAL">&lt;2001:db8::1&gt;/</tt>
 637             </dt>
 638             <dd>
 639               <p>
 640                 Matches any URL with the host address <tt class=
 641                 "LITERAL">2001:db8::1</tt>. (Note that the real URL uses
 642                 plain brackets, not angle brackets.)
 643               </p>
 644             </dd>
 645             <dt>
 646               <tt class="LITERAL">index.html</tt>
 647             </dt>
 648             <dd>
 649               <p>
 650                 matches nothing, since it would be interpreted as a domain
 651                 name and there is no top-level domain called <tt class=
 652                 "LITERAL">.html</tt>. So its a mistake.
 653               </p>
 654             </dd>
 655           </dl>
 656         </div>
 657         <div class="SECT3">
 658           <h3 class="SECT3">
 659             <a name="AEN2843">8.4.1. The Domain Pattern</a>
 660           </h3>
 661           <p>
 662             The matching of the domain part offers some flexible options: if
 663             the domain starts or ends with a dot, it becomes unanchored at
 664             that end. For example:
 665           </p>
 666           <div class="VARIABLELIST">
 667             <dl>
 668               <dt>
 669                 <tt class="LITERAL">.example.com</tt>
 670               </dt>
 671               <dd>
 672                 <p>
 673                   matches any domain with first-level domain <tt class=
 674                   "LITERAL">com</tt> and second-level domain <tt class=
 675                   "LITERAL">example</tt>. For example <tt class=
 676                   "LITERAL">www.example.com</tt>, <tt class=
 677                   "LITERAL">example.com</tt> and <tt class=
 678                   "LITERAL">foo.bar.baz.example.com</tt>. Note that it
 679                   wouldn't match if the second-level domain was <tt class=
 680                   "LITERAL">another-example</tt>.
 681                 </p>
 682               </dd>
 683               <dt>
 684                 <tt class="LITERAL">www.</tt>
 685               </dt>
 686               <dd>
 687                 <p>
 688                   matches any domain that <span class="emphasis"><i class=
 689                   "EMPHASIS">STARTS</i></span> with <tt class=
 690                   "LITERAL">www.</tt> (It also matches the domain <tt class=
 691                   "LITERAL">www</tt> but most of the time that doesn't
 692                   matter.)
 693                 </p>
 694               </dd>
 695               <dt>
 696                 <tt class="LITERAL">.example.</tt>
 697               </dt>
 698               <dd>
 699                 <p>
 700                   matches any domain that <span class="emphasis"><i class=
 701                   "EMPHASIS">CONTAINS</i></span> <tt class=
 702                   "LITERAL">.example.</tt>. And, by the way, also included
 703                   would be any files or documents that exist within that
 704                   domain since no path limitations are specified. (Correctly
 705                   speaking: It matches any FQDN that contains <tt class=
 706                   "LITERAL">example</tt> as a domain.) This might be <tt
 707                   class="LITERAL">www.example.com</tt>, <tt class=
 708                   "LITERAL">news.example.de</tt>, or <tt class=
 709                   "LITERAL">www.example.net/cgi/testing.pl</tt> for instance.
 710                   All these cases are matched.
 711                 </p>
 712               </dd>
 713             </dl>
 714           </div>
 715           <p>
 716             Additionally, there are wild-cards that you can use in the domain
 717             names themselves. These work similarly to shell globbing type
 718             wild-cards: <span class="QUOTE">"*"</span> represents zero or
 719             more arbitrary characters (this is equivalent to the <a href=
 720             "http://en.wikipedia.org/wiki/Regular_expressions" target=
 721             "_top"><span class="QUOTE">"Regular Expression"</span></a> based
 722             syntax of <span class="QUOTE">".*"</span>), <span class=
 723             "QUOTE">"?"</span> represents any single character (this is
 724             equivalent to the regular expression syntax of a simple <span
 725             class="QUOTE">"."</span>), and you can define <span class=
 726             "QUOTE">"character classes"</span> in square brackets which is
 727             similar to the same regular expression technique. All of this can
 728             be freely mixed:
 729           </p>
 730           <div class="VARIABLELIST">
 731             <dl>
 732               <dt>
 733                 <tt class="LITERAL">ad*.example.com</tt>
 734               </dt>
 735               <dd>
 736                 <p>
 737                   matches <span class="QUOTE">"adserver.example.com"</span>,
 738                   <span class="QUOTE">"ads.example.com"</span>, etc but not
 739                   <span class="QUOTE">"sfads.example.com"</span>
 740                 </p>
 741               </dd>
 742               <dt>
 743                 <tt class="LITERAL">*ad*.example.com</tt>
 744               </dt>
 745               <dd>
 746                 <p>
 747                   matches all of the above, and then some.
 748                 </p>
 749               </dd>
 750               <dt>
 751                 <tt class="LITERAL">.?pix.com</tt>
 752               </dt>
 753               <dd>
 754                 <p>
 755                   matches <tt class="LITERAL">www.ipix.com</tt>, <tt class=
 756                   "LITERAL">pictures.epix.com</tt>, <tt class=
 757                   "LITERAL">a.b.c.d.e.upix.com</tt> etc.
 758                 </p>
 759               </dd>
 760               <dt>
 761                 <tt class="LITERAL">www[1-9a-ez].example.c*</tt>
 762               </dt>
 763               <dd>
 764                 <p>
 765                   matches <tt class="LITERAL">www1.example.com</tt>, <tt
 766                   class="LITERAL">www4.example.cc</tt>, <tt class=
 767                   "LITERAL">wwwd.example.cy</tt>, <tt class=
 768                   "LITERAL">wwwz.example.com</tt> etc., but <span class=
 769                   "emphasis"><i class="EMPHASIS">not</i></span> <tt class=
 770                   "LITERAL">wwww.example.com</tt>.
 771                 </p>
 772               </dd>
 773             </dl>
 774           </div>
 775           <p>
 776             While flexible, this is not the sophistication of full regular
 777             expression based syntax.
 778           </p>
 779         </div>
 780         <div class="SECT3">
 781           <h3 class="SECT3">
 782             <a name="AEN2919">8.4.2. The Path Pattern</a>
 783           </h3>
 784           <p>
 785             <span class="APPLICATION">Privoxy</span> uses <span class=
 786             "QUOTE">"modern"</span> POSIX 1003.2 <a href=
 787             "http://en.wikipedia.org/wiki/Regular_expressions" target=
 788             "_top"><span class="QUOTE">"Regular Expressions"</span></a> for
 789             matching the path portion (after the slash), and is thus more
 790             flexible.
 791           </p>
 792           <p>
 793             There is an <a href="appendix.html#REGEX">Appendix</a> with a
 794             brief quick-start into regular expressions, you also might want
 795             to have a look at your operating system's documentation on
 796             regular expressions (try <tt class="LITERAL">man re_format</tt>).
 797           </p>
 798           <p>
 799             Note that the path pattern is automatically left-anchored at the
 800             <span class="QUOTE">"/"</span>, i.e. it matches as if it would
 801             start with a <span class="QUOTE">"^"</span> (regular expression
 802             speak for the beginning of a line).
 803           </p>
 804           <p>
 805             Please also note that matching in the path is <span class=
 806             "emphasis"><i class="EMPHASIS">CASE INSENSITIVE</i></span> by
 807             default, but you can switch to case sensitive at any point in the
 808             pattern by using the <span class="QUOTE">"(?-i)"</span> switch:
 809             <tt class="LITERAL">www.example.com/(?-i)PaTtErN.*</tt> will
 810             match only documents whose path starts with <tt class=
 811             "LITERAL">PaTtErN</tt> in <span class="emphasis"><i class=
 812             "EMPHASIS">exactly</i></span> this capitalization.
 813           </p>
 814           <div class="VARIABLELIST">
 815             <dl>
 816               <dt>
 817                 <tt class="LITERAL">.example.com/.*</tt>
 818               </dt>
 819               <dd>
 820                 <p>
 821                   Is equivalent to just <span class=
 822                   "QUOTE">".example.com"</span>, since any documents within
 823                   that domain are matched with or without the <span class=
 824                   "QUOTE">".*"</span> regular expression. This is redundant
 825                 </p>
 826               </dd>
 827               <dt>
 828                 <tt class="LITERAL">.example.com/.*/index.html$</tt>
 829               </dt>
 830               <dd>
 831                 <p>
 832                   Will match any page in the domain of <span class=
 833                   "QUOTE">"example.com"</span> that is named <span class=
 834                   "QUOTE">"index.html"</span>, and that is part of some path.
 835                   For example, it matches <span class=
 836                   "QUOTE">"www.example.com/testing/index.html"</span> but NOT
 837                   <span class="QUOTE">"www.example.com/index.html"</span>
 838                   because the regular expression called for at least two
 839                   <span class="QUOTE">"/'s"</span>, thus the path
 840                   requirement. It also would match <span class=
 841                   "QUOTE">"www.example.com/testing/index_html"</span>,
 842                   because of the special meta-character <span class=
 843                   "QUOTE">"."</span>.
 844                 </p>
 845               </dd>
 846               <dt>
 847                 <tt class="LITERAL">.example.com/(.*/)?index\.html$</tt>
 848               </dt>
 849               <dd>
 850                 <p>
 851                   This regular expression is conditional so it will match any
 852                   page named <span class="QUOTE">"index.html"</span>
 853                   regardless of path which in this case can have one or more
 854                   <span class="QUOTE">"/'s"</span>. And this one must contain
 855                   exactly <span class="QUOTE">".html"</span> (but does not
 856                   have to end with that!).
 857                 </p>
 858               </dd>
 859               <dt>
 860                 <tt class=
 861                 "LITERAL">.example.com/(.*/)(ads|banners?|junk)</tt>
 862               </dt>
 863               <dd>
 864                 <p>
 865                   This regular expression will match any path of <span class=
 866                   "QUOTE">"example.com"</span> that contains any of the words
 867                   <span class="QUOTE">"ads"</span>, <span class=
 868                   "QUOTE">"banner"</span>, <span class=
 869                   "QUOTE">"banners"</span> (because of the <span class=
 870                   "QUOTE">"?"</span>) or <span class="QUOTE">"junk"</span>.
 871                   The path does not have to end in these words, just contain
 872                   them.
 873                 </p>
 874               </dd>
 875               <dt>
 876                 <tt class=
 877                 "LITERAL">.example.com/(.*/)(ads|banners?|junk)/.*\.(jpe?g|gif|png)$</tt>
 878               </dt>
 879               <dd>
 880                 <p>
 881                   This is very much the same as above, except now it must end
 882                   in either <span class="QUOTE">".jpg"</span>, <span class=
 883                   "QUOTE">".jpeg"</span>, <span class="QUOTE">".gif"</span>
 884                   or <span class="QUOTE">".png"</span>. So this one is
 885                   limited to common image formats.
 886                 </p>
 887               </dd>
 888             </dl>
 889           </div>
 890           <p>
 891             There are many, many good examples to be found in <tt class=
 892             "FILENAME">default.action</tt>, and more tutorials below in <a
 893             href="appendix.html#REGEX">Appendix on regular expressions</a>.
 894           </p>
 895         </div>
 896         <div class="SECT3">
 897           <h3 class="SECT3">
 898             <a name="TAG-PATTERN">8.4.3. The Tag Pattern</a>
 899           </h3>
 900           <p>
 901             Tag patterns are used to change the applying actions based on the
 902             request's tags. Tags can be created with either the <a href=
 903             "actions-file.html#CLIENT-HEADER-TAGGER">client-header-tagger</a>
 904             or the <a href=
 905             "actions-file.html#SERVER-HEADER-TAGGER">server-header-tagger</a>
 906             action.
 907           </p>
 908           <p>
 909             Tag patterns have to start with <span class=
 910             "QUOTE">"TAG:"</span>, so <span class=
 911             "APPLICATION">Privoxy</span> can tell them apart from URL
 912             patterns. Everything after the colon including white space, is
 913             interpreted as a regular expression with path pattern syntax,
 914             except that tag patterns aren't left-anchored automatically
 915             (<span class="APPLICATION">Privoxy</span> doesn't silently add a
 916             <span class="QUOTE">"^"</span>, you have to do it yourself if you
 917             need it).
 918           </p>
 919           <p>
 920             To match all requests that are tagged with <span class=
 921             "QUOTE">"foo"</span> your pattern line should be <span class=
 922             "QUOTE">"TAG:^foo$"</span>, <span class="QUOTE">"TAG:foo"</span>
 923             would work as well, but it would also match requests whose tags
 924             contain <span class="QUOTE">"foo"</span> somewhere. <span class=
 925             "QUOTE">"TAG: foo"</span> wouldn't work as it requires white
 926             space.
 927           </p>
 928           <p>
 929             Sections can contain URL and tag patterns at the same time, but
 930             tag patterns are checked after the URL patterns and thus always
 931             overrule them, even if they are located before the URL patterns.
 932           </p>
 933           <p>
 934             Once a new tag is added, Privoxy checks right away if it's
 935             matched by one of the tag patterns and updates the action
 936             settings accordingly. As a result tags can be used to activate
 937             other tagger actions, as long as these other taggers look for
 938             headers that haven't already be parsed.
 939           </p>
 940           <p>
 941             For example you could tag client requests which use the <tt
 942             class="LITERAL">POST</tt> method, then use this tag to activate
 943             another tagger that adds a tag if cookies are sent, and then use
 944             a block action based on the cookie tag. This allows the outcome
 945             of one action, to be input into a subsequent action. However if
 946             you'd reverse the position of the described taggers, and
 947             activated the method tagger based on the cookie tagger, no method
 948             tags would be created. The method tagger would look for the
 949             request line, but at the time the cookie tag is created, the
 950             request line has already been parsed.
 951           </p>
 952           <p>
 953             While this is a limitation you should be aware of, this kind of
 954             indirection is seldom needed anyway and even the example doesn't
 955             make too much sense.
 956           </p>
 957         </div>
 958       </div>
 959       <div class="SECT2">
 960         <h2 class="SECT2">
 961           <a name="ACTIONS">8.5. Actions</a>
 962         </h2>
 963         <p>
 964           All actions are disabled by default, until they are explicitly
 965           enabled somewhere in an actions file. Actions are turned on if
 966           preceded with a <span class="QUOTE">"+"</span>, and turned off if
 967           preceded with a <span class="QUOTE">"-"</span>. So a <tt class=
 968           "LITERAL">+action</tt> means <span class="QUOTE">"do that
 969           action"</span>, e.g. <tt class="LITERAL">+block</tt> means <span
 970           class="QUOTE">"please block URLs that match the following
 971           patterns"</span>, and <tt class="LITERAL">-block</tt> means <span
 972           class="QUOTE">"don't block URLs that match the following patterns,
 973           even if <tt class="LITERAL">+block</tt> previously
 974           applied."</span>&#13;
 975         </p>
 976         <p>
 977           Again, actions are invoked by placing them on a line, enclosed in
 978           curly braces and separated by whitespace, like in <tt class=
 979           "LITERAL">{+some-action -some-other-action{some-parameter}}</tt>,
 980           followed by a list of URL patterns, one per line, to which they
 981           apply. Together, the actions line and the following pattern lines
 982           make up a section of the actions file.
 983         </p>
 984         <p>
 985           Actions fall into three categories:
 986         </p>
 987         <p>
 988         </p>
 989         <ul>
 990           <li>
 991             <p>
 992               Boolean, i.e the action can only be <span class=
 993               "QUOTE">"enabled"</span> or <span class=
 994               "QUOTE">"disabled"</span>. Syntax:
 995             </p>
 996             <p>
 997             </p>
 998             <table border="0" bgcolor="#E0E0E0" width="90%">
 999               <tr>
1000                 <td>
1001 <pre class="SCREEN">
1002   +<tt class="REPLACEABLE"><i>name</i></tt>        # enable action <tt class=
1003 "REPLACEABLE"><i>name</i></tt>
1004   -<tt class="REPLACEABLE"><i>name</i></tt>        # disable action <tt
1005 class="REPLACEABLE"><i>name</i></tt>
1006 </pre>
1007                 </td>
1008               </tr>
1009             </table>
1010
1011             <p>
1012               Example: <tt class="LITERAL">+handle-as-image</tt>
1013             </p>
1014           </li>
1015           <li>
1016             <p>
1017               Parameterized, where some value is required in order to enable
1018               this type of action. Syntax:
1019             </p>
1020             <p>
1021             </p>
1022             <table border="0" bgcolor="#E0E0E0" width="90%">
1023               <tr>
1024                 <td>
1025 <pre class="SCREEN">
1026   +<tt class="REPLACEABLE"><i>name</i></tt>{<tt class=
1027 "REPLACEABLE"><i>param</i></tt>}  # enable action and set parameter to <tt
1028 class="REPLACEABLE"><i>param</i></tt>,
1029                # overwriting parameter from previous match if necessary
1030   -<tt class=
1031 "REPLACEABLE"><i>name</i></tt>         # disable action. The parameter can be omitted
1032 </pre>
1033                 </td>
1034               </tr>
1035             </table>
1036
1037             <p>
1038               Note that if the URL matches multiple positive forms of a
1039               parameterized action, the last match wins, i.e. the params from
1040               earlier matches are simply ignored.
1041             </p>
1042             <p>
1043               Example: <tt class="LITERAL">+hide-user-agent{Mozilla/5.0 (X11;
1044               U; FreeBSD i386; en-US; rv:1.8.1.4) Gecko/20070602
1045               Firefox/2.0.0.4}</tt>
1046             </p>
1047           </li>
1048           <li>
1049             <p>
1050               Multi-value. These look exactly like parameterized actions, but
1051               they behave differently: If the action applies multiple times
1052               to the same URL, but with different parameters, <span class=
1053               "emphasis"><i class="EMPHASIS">all</i></span> the parameters
1054               from <span class="emphasis"><i class="EMPHASIS">all</i></span>
1055               matches are remembered. This is used for actions that can be
1056               executed for the same request repeatedly, like adding multiple
1057               headers, or filtering through multiple filters. Syntax:
1058             </p>
1059             <p>
1060             </p>
1061             <table border="0" bgcolor="#E0E0E0" width="90%">
1062               <tr>
1063                 <td>
1064 <pre class="SCREEN">
1065   +<tt class="REPLACEABLE"><i>name</i></tt>{<tt class=
1066 "REPLACEABLE"><i>param</i></tt>}   # enable action and add <tt class=
1067 "REPLACEABLE"><i>param</i></tt> to the list of parameters
1068   -<tt class="REPLACEABLE"><i>name</i></tt>{<tt class=
1069 "REPLACEABLE"><i>param</i></tt>}   # remove the parameter <tt class=
1070 "REPLACEABLE"><i>param</i></tt> from the list of parameters
1071                 # If it was the last one left, disable the action.
1072   <tt class=
1073 "REPLACEABLE"><i>-name</i></tt>          # disable this action completely and remove all parameters from the list
1074 </pre>
1075                 </td>
1076               </tr>
1077             </table>
1078
1079             <p>
1080               Examples: <tt class="LITERAL">+add-header{X-Fun-Header: Some
1081               text}</tt> and <tt class=
1082               "LITERAL">+filter{html-annoyances}</tt>
1083             </p>
1084           </li>
1085         </ul>
1086
1087         <p>
1088           If nothing is specified in any actions file, no <span class=
1089           "QUOTE">"actions"</span> are taken. So in this case <span class=
1090           "APPLICATION">Privoxy</span> would just be a normal, non-blocking,
1091           non-filtering proxy. You must specifically enable the privacy and
1092           blocking features you need (although the provided default actions
1093           files will give a good starting point).
1094         </p>
1095         <p>
1096           Later defined action sections always over-ride earlier ones of the
1097           same type. So exceptions to any rules you make, should come in the
1098           latter part of the file (or in a file that is processed later when
1099           using multiple actions files such as <tt class=
1100           "FILENAME">user.action</tt>). For multi-valued actions, the actions
1101           are applied in the order they are specified. Actions files are
1102           processed in the order they are defined in <tt class=
1103           "FILENAME">config</tt> (the default installation has three actions
1104           files). It also quite possible for any given URL to match more than
1105           one <span class="QUOTE">"pattern"</span> (because of wildcards and
1106           regular expressions), and thus to trigger more than one set of
1107           actions! Last match wins.
1108         </p>
1109         <p>
1110           The list of valid <span class="APPLICATION">Privoxy</span> actions
1111           are:
1112         </p>
1113         <div class="SECT3">
1114           <h4 class="SECT3">
1115             <a name="ADD-HEADER">8.5.1. add-header</a>
1116           </h4>
1117           <div class="VARIABLELIST">
1118             <dl>
1119               <dt>
1120                 Typical use:
1121               </dt>
1122               <dd>
1123                 <p>
1124                   Confuse log analysis, custom applications
1125                 </p>
1126               </dd>
1127               <dt>
1128                 Effect:
1129               </dt>
1130               <dd>
1131                 <p>
1132                   Sends a user defined HTTP header to the web server.
1133                 </p>
1134               </dd>
1135               <dt>
1136                 Type:
1137               </dt>
1138               <dd>
1139                 <p>
1140                   Multi-value.
1141                 </p>
1142               </dd>
1143               <dt>
1144                 Parameter:
1145               </dt>
1146               <dd>
1147                 <p>
1148                   Any string value is possible. Validity of the defined HTTP
1149                   headers is not checked. It is recommended that you use the
1150                   <span class="QUOTE">"<tt class="LITERAL">X-</tt>"</span>
1151                   prefix for custom headers.
1152                 </p>
1153               </dd>
1154               <dt>
1155                 Notes:
1156               </dt>
1157               <dd>
1158                 <p>
1159                   This action may be specified multiple times, in order to
1160                   define multiple headers. This is rarely needed for the
1161                   typical user. If you don't know what <span class=
1162                   "QUOTE">"HTTP headers"</span> are, you definitely don't
1163                   need to worry about this one.
1164                 </p>
1165                 <p>
1166                   Headers added by this action are not modified by other
1167                   actions.
1168                 </p>
1169               </dd>
1170               <dt>
1171                 Example usage:
1172               </dt>
1173               <dd>
1174                 <p>
1175                 </p>
1176                 <table border="0" bgcolor="#E0E0E0" width="90%">
1177                   <tr>
1178                     <td>
1179 <pre class="SCREEN">
1180 +add-header{X-User-Tracking: sucks}
1181 </pre>
1182                     </td>
1183                   </tr>
1184                 </table>
1185               </dd>
1186             </dl>
1187           </div>
1188         </div>
1189         <div class="SECT3">
1190           <h4 class="SECT3">
1191             <a name="BLOCK">8.5.2. block</a>
1192           </h4>
1193           <div class="VARIABLELIST">
1194             <dl>
1195               <dt>
1196                 Typical use:
1197               </dt>
1198               <dd>
1199                 <p>
1200                   Block ads or other unwanted content
1201                 </p>
1202               </dd>
1203               <dt>
1204                 Effect:
1205               </dt>
1206               <dd>
1207                 <p>
1208                   Requests for URLs to which this action applies are blocked,
1209                   i.e. the requests are trapped by <span class=
1210                   "APPLICATION">Privoxy</span> and the requested URL is never
1211                   retrieved, but is answered locally with a substitute page
1212                   or image, as determined by the <tt class="LITERAL"><a href=
1213                   "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a></tt>,
1214                   <tt class="LITERAL"><a href=
1215                   "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker</a></tt>,
1216                   and <tt class="LITERAL"><a href=
1217                   "actions-file.html#HANDLE-AS-EMPTY-DOCUMENT">handle-as-empty-document</a></tt>
1218                   actions.
1219                 </p>
1220               </dd>
1221               <dt>
1222                 Type:
1223               </dt>
1224               <dd>
1225                 <p>
1226                   Parameterized.
1227                 </p>
1228               </dd>
1229               <dt>
1230                 Parameter:
1231               </dt>
1232               <dd>
1233                 <p>
1234                   A block reason that should be given to the user.
1235                 </p>
1236               </dd>
1237               <dt>
1238                 Notes:
1239               </dt>
1240               <dd>
1241                 <p>
1242                   <span class="APPLICATION">Privoxy</span> sends a special
1243                   <span class="QUOTE">"BLOCKED"</span> page for requests to
1244                   blocked pages. This page contains the block reason given as
1245                   parameter, a link to find out why the block action applies,
1246                   and a click-through to the blocked content (the latter only
1247                   if the force feature is available and enabled).
1248                 </p>
1249                 <p>
1250                   A very important exception occurs if <span class=
1251                   "emphasis"><i class="EMPHASIS">both</i></span> <tt class=
1252                   "LITERAL">block</tt> and <tt class="LITERAL"><a href=
1253                   "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a></tt>,
1254                   apply to the same request: it will then be replaced by an
1255                   image. If <tt class="LITERAL"><a href=
1256                   "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker</a></tt>
1257                   (see below) also applies, the type of image will be
1258                   determined by its parameter, if not, the standard
1259                   checkerboard pattern is sent.
1260                 </p>
1261                 <p>
1262                   It is important to understand this process, in order to
1263                   understand how <span class="APPLICATION">Privoxy</span>
1264                   deals with ads and other unwanted content. Blocking is a
1265                   core feature, and one upon which various other features
1266                   depend.
1267                 </p>
1268                 <p>
1269                   The <tt class="LITERAL"><a href=
1270                   "actions-file.html#FILTER">filter</a></tt> action can
1271                   perform a very similar task, by <span class=
1272                   "QUOTE">"blocking"</span> banner images and other content
1273                   through rewriting the relevant URLs in the document's HTML
1274                   source, so they don't get requested in the first place.
1275                   Note that this is a totally different technique, and it's
1276                   easy to confuse the two.
1277                 </p>
1278               </dd>
1279               <dt>
1280                 Example usage (section):
1281               </dt>
1282               <dd>
1283                 <p>
1284                 </p>
1285                 <table border="0" bgcolor="#E0E0E0" width="90%">
1286                   <tr>
1287                     <td>
1288 <pre class="SCREEN">
1289 {+block{No nasty stuff for you.}}
1290 # Block and replace with "blocked" page
1291  .nasty-stuff.example.com
1292
1293 {+block{Doubleclick banners.} +handle-as-image}
1294 # Block and replace with image
1295  .ad.doubleclick.net
1296  .ads.r.us/banners/
1297
1298 {+block{Layered ads.} +handle-as-empty-document}
1299 # Block and then ignore
1300  adserver.example.net/.*\.js$
1301 </pre>
1302                     </td>
1303                   </tr>
1304                 </table>
1305               </dd>
1306             </dl>
1307           </div>
1308         </div>
1309         <div class="SECT3">
1310           <h4 class="SECT3">
1311             <a name="CHANGE-X-FORWARDED-FOR">8.5.3.
1312             change-x-forwarded-for</a>
1313           </h4>
1314           <div class="VARIABLELIST">
1315             <dl>
1316               <dt>
1317                 Typical use:
1318               </dt>
1319               <dd>
1320                 <p>
1321                   Improve privacy by not forwarding the source of the request
1322                   in the HTTP headers.
1323                 </p>
1324               </dd>
1325               <dt>
1326                 Effect:
1327               </dt>
1328               <dd>
1329                 <p>
1330                   Deletes the <span class="QUOTE">"X-Forwarded-For:"</span>
1331                   HTTP header from the client request, or adds a new one.
1332                 </p>
1333               </dd>
1334               <dt>
1335                 Type:
1336               </dt>
1337               <dd>
1338                 <p>
1339                   Parameterized.
1340                 </p>
1341               </dd>
1342               <dt>
1343                 Parameter:
1344               </dt>
1345               <dd>
1346                 <ul>
1347                   <li>
1348                     <p>
1349                       <span class="QUOTE">"block"</span> to delete the
1350                       header.
1351                     </p>
1352                   </li>
1353                   <li>
1354                     <p>
1355                       <span class="QUOTE">"add"</span> to create the header
1356                       (or append the client's IP address to an already
1357                       existing one).
1358                     </p>
1359                   </li>
1360                 </ul>
1361               </dd>
1362               <dt>
1363                 Notes:
1364               </dt>
1365               <dd>
1366                 <p>
1367                   It is safe and recommended to use <tt class=
1368                   "LITERAL">block</tt>.
1369                 </p>
1370                 <p>
1371                   Forwarding the source address of the request may make sense
1372                   in some multi-user setups but is also a privacy risk.
1373                 </p>
1374               </dd>
1375               <dt>
1376                 Example usage:
1377               </dt>
1378               <dd>
1379                 <p>
1380                 </p>
1381                 <table border="0" bgcolor="#E0E0E0" width="90%">
1382                   <tr>
1383                     <td>
1384 <pre class="SCREEN">
1385 +change-x-forwarded-for{block}
1386 </pre>
1387                     </td>
1388                   </tr>
1389                 </table>
1390               </dd>
1391             </dl>
1392           </div>
1393         </div>
1394         <div class="SECT3">
1395           <h4 class="SECT3">
1396             <a name="CLIENT-HEADER-FILTER">8.5.4. client-header-filter</a>
1397           </h4>
1398           <div class="VARIABLELIST">
1399             <dl>
1400               <dt>
1401                 Typical use:
1402               </dt>
1403               <dd>
1404                 <p>
1405                   Rewrite or remove single client headers.
1406                 </p>
1407               </dd>
1408               <dt>
1409                 Effect:
1410               </dt>
1411               <dd>
1412                 <p>
1413                   All client headers to which this action applies are
1414                   filtered on-the-fly through the specified regular
1415                   expression based substitutions.
1416                 </p>
1417               </dd>
1418               <dt>
1419                 Type:
1420               </dt>
1421               <dd>
1422                 <p>
1423                   Parameterized.
1424                 </p>
1425               </dd>
1426               <dt>
1427                 Parameter:
1428               </dt>
1429               <dd>
1430                 <p>
1431                   The name of a client-header filter, as defined in one of
1432                   the <a href="filter-file.html">filter files</a>.
1433                 </p>
1434               </dd>
1435               <dt>
1436                 Notes:
1437               </dt>
1438               <dd>
1439                 <p>
1440                   Client-header filters are applied to each header on its
1441                   own, not to all at once. This makes it easier to diagnose
1442                   problems, but on the downside you can't write filters that
1443                   only change header x if header y's value is z. You can do
1444                   that by using tags though.
1445                 </p>
1446                 <p>
1447                   Client-header filters are executed after the other header
1448                   actions have finished and use their output as input.
1449                 </p>
1450                 <p>
1451                   If the request URL gets changed, <span class=
1452                   "APPLICATION">Privoxy</span> will detect that and use the
1453                   new one. This can be used to rewrite the request
1454                   destination behind the client's back, for example to
1455                   specify a Tor exit relay for certain requests.
1456                 </p>
1457                 <p>
1458                   Please refer to the <a href="filter-file.html">filter file
1459                   chapter</a> to learn which client-header filters are
1460                   available by default, and how to create your own.
1461                 </p>
1462               </dd>
1463               <dt>
1464                 Example usage (section):
1465               </dt>
1466               <dd>
1467                 <p>
1468                 </p>
1469                 <table border="0" bgcolor="#E0E0E0" width="90%">
1470                   <tr>
1471                     <td>
1472 <pre class="SCREEN">
1473 # Hide Tor exit notation in Host and Referer Headers
1474 {+client-header-filter{hide-tor-exit-notation}}
1475 /
1476
1477 </pre>
1478                     </td>
1479                   </tr>
1480                 </table>
1481               </dd>
1482             </dl>
1483           </div>
1484         </div>
1485         <div class="SECT3">
1486           <h4 class="SECT3">
1487             <a name="CLIENT-HEADER-TAGGER">8.5.5. client-header-tagger</a>
1488           </h4>
1489           <div class="VARIABLELIST">
1490             <dl>
1491               <dt>
1492                 Typical use:
1493               </dt>
1494               <dd>
1495                 <p>
1496                   Block requests based on their headers.
1497                 </p>
1498               </dd>
1499               <dt>
1500                 Effect:
1501               </dt>
1502               <dd>
1503                 <p>
1504                   Client headers to which this action applies are filtered
1505                   on-the-fly through the specified regular expression based
1506                   substitutions, the result is used as tag.
1507                 </p>
1508               </dd>
1509               <dt>
1510                 Type:
1511               </dt>
1512               <dd>
1513                 <p>
1514                   Parameterized.
1515                 </p>
1516               </dd>
1517               <dt>
1518                 Parameter:
1519               </dt>
1520               <dd>
1521                 <p>
1522                   The name of a client-header tagger, as defined in one of
1523                   the <a href="filter-file.html">filter files</a>.
1524                 </p>
1525               </dd>
1526               <dt>
1527                 Notes:
1528               </dt>
1529               <dd>
1530                 <p>
1531                   Client-header taggers are applied to each header on its
1532                   own, and as the header isn't modified, each tagger <span
1533                   class="QUOTE">"sees"</span> the original.
1534                 </p>
1535                 <p>
1536                   Client-header taggers are the first actions that are
1537                   executed and their tags can be used to control every other
1538                   action.
1539                 </p>
1540               </dd>
1541               <dt>
1542                 Example usage (section):
1543               </dt>
1544               <dd>
1545                 <p>
1546                 </p>
1547                 <table border="0" bgcolor="#E0E0E0" width="90%">
1548                   <tr>
1549                     <td>
1550 <pre class="SCREEN">
1551 # Tag every request with the User-Agent header
1552 {+client-header-tagger{user-agent}}
1553 /
1554
1555 # Tagging itself doesn't change the action
1556 # settings, sections with TAG patterns do:
1557 #
1558 # If it's a download agent, use a different forwarding proxy,
1559 # show the real User-Agent and make sure resume works.
1560 {+forward-override{forward-socks5 10.0.0.2:2222 .} \
1561  -hide-if-modified-since      \
1562  -overwrite-last-modified     \
1563  -hide-user-agent             \
1564  -filter                      \
1565  -deanimate-gifs              \
1566 }
1567 TAG:^User-Agent: NetBSD-ftp/
1568 TAG:^User-Agent: Novell ZYPP Installer
1569 TAG:^User-Agent: RPM APT-HTTP/
1570 TAG:^User-Agent: fetch libfetch/
1571 TAG:^User-Agent: Ubuntu APT-HTTP/
1572 TAG:^User-Agent: MPlayer/
1573
1574 </pre>
1575                     </td>
1576                   </tr>
1577                 </table>
1578               </dd>
1579             </dl>
1580           </div>
1581         </div>
1582         <div class="SECT3">
1583           <h4 class="SECT3">
1584             <a name="CONTENT-TYPE-OVERWRITE">8.5.6.
1585             content-type-overwrite</a>
1586           </h4>
1587           <div class="VARIABLELIST">
1588             <dl>
1589               <dt>
1590                 Typical use:
1591               </dt>
1592               <dd>
1593                 <p>
1594                   Stop useless download menus from popping up, or change the
1595                   browser's rendering mode
1596                 </p>
1597               </dd>
1598               <dt>
1599                 Effect:
1600               </dt>
1601               <dd>
1602                 <p>
1603                   Replaces the <span class="QUOTE">"Content-Type:"</span>
1604                   HTTP server header.
1605                 </p>
1606               </dd>
1607               <dt>
1608                 Type:
1609               </dt>
1610               <dd>
1611                 <p>
1612                   Parameterized.
1613                 </p>
1614               </dd>
1615               <dt>
1616                 Parameter:
1617               </dt>
1618               <dd>
1619                 <p>
1620                   Any string.
1621                 </p>
1622               </dd>
1623               <dt>
1624                 Notes:
1625               </dt>
1626               <dd>
1627                 <p>
1628                   The <span class="QUOTE">"Content-Type:"</span> HTTP server
1629                   header is used by the browser to decide what to do with the
1630                   document. The value of this header can cause the browser to
1631                   open a download menu instead of displaying the document by
1632                   itself, even if the document's format is supported by the
1633                   browser.
1634                 </p>
1635                 <p>
1636                   The declared content type can also affect which rendering
1637                   mode the browser chooses. If XHTML is delivered as <span
1638                   class="QUOTE">"text/html"</span>, many browsers treat it as
1639                   yet another broken HTML document. If it is send as <span
1640                   class="QUOTE">"application/xml"</span>, browsers with XHTML
1641                   support will only display it, if the syntax is correct.
1642                 </p>
1643                 <p>
1644                   If you see a web site that proudly uses XHTML buttons, but
1645                   sets <span class="QUOTE">"Content-Type: text/html"</span>,
1646                   you can use <span class="APPLICATION">Privoxy</span> to
1647                   overwrite it with <span class=
1648                   "QUOTE">"application/xml"</span> and validate the web
1649                   master's claim inside your XHTML-supporting browser. If the
1650                   syntax is incorrect, the browser will complain loudly.
1651                 </p>
1652                 <p>
1653                   You can also go the opposite direction: if your browser
1654                   prints error messages instead of rendering a document
1655                   falsely declared as XHTML, you can overwrite the content
1656                   type with <span class="QUOTE">"text/html"</span> and have
1657                   it rendered as broken HTML document.
1658                 </p>
1659                 <p>
1660                   By default <tt class="LITERAL">content-type-overwrite</tt>
1661                   only replaces <span class="QUOTE">"Content-Type:"</span>
1662                   headers that look like some kind of text. If you want to
1663                   overwrite it unconditionally, you have to combine it with
1664                   <tt class="LITERAL"><a href=
1665                   "actions-file.html#FORCE-TEXT-MODE">force-text-mode</a></tt>.
1666                   This limitation exists for a reason, think twice before
1667                   circumventing it.
1668                 </p>
1669                 <p>
1670                   Most of the time it's easier to replace this action with a
1671                   custom <tt class="LITERAL"><a href=
1672                   "actions-file.html#SERVER-HEADER-FILTER">server-header
1673                   filter</a></tt>. It allows you to activate it for every
1674                   document of a certain site and it will still only replace
1675                   the content types you aimed at.
1676                 </p>
1677                 <p>
1678                   Of course you can apply <tt class=
1679                   "LITERAL">content-type-overwrite</tt> to a whole site and
1680                   then make URL based exceptions, but it's a lot more work to
1681                   get the same precision.
1682                 </p>
1683               </dd>
1684               <dt>
1685                 Example usage (sections):
1686               </dt>
1687               <dd>
1688                 <p>
1689                 </p>
1690                 <table border="0" bgcolor="#E0E0E0" width="90%">
1691                   <tr>
1692                     <td>
1693 <pre class="SCREEN">
1694 # Check if www.example.net/ really uses valid XHTML
1695 { +content-type-overwrite{application/xml} }
1696 www.example.net/
1697
1698 # but leave the content type unmodified if the URL looks like a style sheet
1699 {-content-type-overwrite}
1700 www.example.net/.*\.css$
1701 www.example.net/.*style
1702 </pre>
1703                     </td>
1704                   </tr>
1705                 </table>
1706               </dd>
1707             </dl>
1708           </div>
1709         </div>
1710         <div class="SECT3">
1711           <h4 class="SECT3">
1712             <a name="CRUNCH-CLIENT-HEADER">8.5.7. crunch-client-header</a>
1713           </h4>
1714           <div class="VARIABLELIST">
1715             <dl>
1716               <dt>
1717                 Typical use:
1718               </dt>
1719               <dd>
1720                 <p>
1721                   Remove a client header <span class=
1722                   "APPLICATION">Privoxy</span> has no dedicated action for.
1723                 </p>
1724               </dd>
1725               <dt>
1726                 Effect:
1727               </dt>
1728               <dd>
1729                 <p>
1730                   Deletes every header sent by the client that contains the
1731                   string the user supplied as parameter.
1732                 </p>
1733               </dd>
1734               <dt>
1735                 Type:
1736               </dt>
1737               <dd>
1738                 <p>
1739                   Parameterized.
1740                 </p>
1741               </dd>
1742               <dt>
1743                 Parameter:
1744               </dt>
1745               <dd>
1746                 <p>
1747                   Any string.
1748                 </p>
1749               </dd>
1750               <dt>
1751                 Notes:
1752               </dt>
1753               <dd>
1754                 <p>
1755                   This action allows you to block client headers for which no
1756                   dedicated <span class="APPLICATION">Privoxy</span> action
1757                   exists. <span class="APPLICATION">Privoxy</span> will
1758                   remove every client header that contains the string you
1759                   supplied as parameter.
1760                 </p>
1761                 <p>
1762                   Regular expressions are <span class="emphasis"><i class=
1763                   "EMPHASIS">not supported</i></span> and you can't use this
1764                   action to block different headers in the same request,
1765                   unless they contain the same string.
1766                 </p>
1767                 <p>
1768                   <tt class="LITERAL">crunch-client-header</tt> is only meant
1769                   for quick tests. If you have to block several different
1770                   headers, or only want to modify parts of them, you should
1771                   use a <tt class="LITERAL"><a href=
1772                   "actions-file.html#CLIENT-HEADER-FILTER">client-header
1773                   filter</a></tt>.
1774                 </p>
1775                 <div class="WARNING">
1776                   <table class="WARNING" border="1" width="90%">
1777                     <tr>
1778                       <td align="CENTER">
1779                         <b>Warning</b>
1780                       </td>
1781                     </tr>
1782                     <tr>
1783                       <td align="LEFT">
1784                         <p>
1785                           Don't block any header without understanding the
1786                           consequences.
1787                         </p>
1788                       </td>
1789                     </tr>
1790                   </table>
1791                 </div>
1792               </dd>
1793               <dt>
1794                 Example usage (section):
1795               </dt>
1796               <dd>
1797                 <p>
1798                 </p>
1799                 <table border="0" bgcolor="#E0E0E0" width="90%">
1800                   <tr>
1801                     <td>
1802 <pre class="SCREEN">
1803 # Block the non-existent "Privacy-Violation:" client header
1804 { +crunch-client-header{Privacy-Violation:} }
1805 /
1806
1807 </pre>
1808                     </td>
1809                   </tr>
1810                 </table>
1811               </dd>
1812             </dl>
1813           </div>
1814         </div>
1815         <div class="SECT3">
1816           <h4 class="SECT3">
1817             <a name="CRUNCH-IF-NONE-MATCH">8.5.8. crunch-if-none-match</a>
1818           </h4>
1819           <div class="VARIABLELIST">
1820             <dl>
1821               <dt>
1822                 Typical use:
1823               </dt>
1824               <dd>
1825                 <p>
1826                   Prevent yet another way to track the user's steps between
1827                   sessions.
1828                 </p>
1829               </dd>
1830               <dt>
1831                 Effect:
1832               </dt>
1833               <dd>
1834                 <p>
1835                   Deletes the <span class="QUOTE">"If-None-Match:"</span>
1836                   HTTP client header.
1837                 </p>
1838               </dd>
1839               <dt>
1840                 Type:
1841               </dt>
1842               <dd>
1843                 <p>
1844                   Boolean.
1845                 </p>
1846               </dd>
1847               <dt>
1848                 Parameter:
1849               </dt>
1850               <dd>
1851                 <p>
1852                   N/A
1853                 </p>
1854               </dd>
1855               <dt>
1856                 Notes:
1857               </dt>
1858               <dd>
1859                 <p>
1860                   Removing the <span class="QUOTE">"If-None-Match:"</span>
1861                   HTTP client header is useful for filter testing, where you
1862                   want to force a real reload instead of getting status code
1863                   <span class="QUOTE">"304"</span> which would cause the
1864                   browser to use a cached copy of the page.
1865                 </p>
1866                 <p>
1867                   It is also useful to make sure the header isn't used as a
1868                   cookie replacement (unlikely but possible).
1869                 </p>
1870                 <p>
1871                   Blocking the <span class="QUOTE">"If-None-Match:"</span>
1872                   header shouldn't cause any caching problems, as long as the
1873                   <span class="QUOTE">"If-Modified-Since:"</span> header
1874                   isn't blocked or missing as well.
1875                 </p>
1876                 <p>
1877                   It is recommended to use this action together with <tt
1878                   class="LITERAL"><a href=
1879                   "actions-file.html#HIDE-IF-MODIFIED-SINCE">hide-if-modified-since</a></tt>
1880                   and <tt class="LITERAL"><a href=
1881                   "actions-file.html#OVERWRITE-LAST-MODIFIED">overwrite-last-modified</a></tt>.
1882                 </p>
1883               </dd>
1884               <dt>
1885                 Example usage (section):
1886               </dt>
1887               <dd>
1888                 <p>
1889                 </p>
1890                 <table border="0" bgcolor="#E0E0E0" width="90%">
1891                   <tr>
1892                     <td>
1893 <pre class="SCREEN">
1894 # Let the browser revalidate cached documents but don't
1895 # allow the server to use the revalidation headers for user tracking.
1896 {+hide-if-modified-since{-60} \
1897  +overwrite-last-modified{randomize} \
1898  +crunch-if-none-match}
1899 /
1900 </pre>
1901                     </td>
1902                   </tr>
1903                 </table>
1904               </dd>
1905             </dl>
1906           </div>
1907         </div>
1908         <div class="SECT3">
1909           <h4 class="SECT3">
1910             <a name="CRUNCH-INCOMING-COOKIES">8.5.9.
1911             crunch-incoming-cookies</a>
1912           </h4>
1913           <div class="VARIABLELIST">
1914             <dl>
1915               <dt>
1916                 Typical use:
1917               </dt>
1918               <dd>
1919                 <p>
1920                   Prevent the web server from setting HTTP cookies on your
1921                   system
1922                 </p>
1923               </dd>
1924               <dt>
1925                 Effect:
1926               </dt>
1927               <dd>
1928                 <p>
1929                   Deletes any <span class="QUOTE">"Set-Cookie:"</span> HTTP
1930                   headers from server replies.
1931                 </p>
1932               </dd>
1933               <dt>
1934                 Type:
1935               </dt>
1936               <dd>
1937                 <p>
1938                   Boolean.
1939                 </p>
1940               </dd>
1941               <dt>
1942                 Parameter:
1943               </dt>
1944               <dd>
1945                 <p>
1946                   N/A
1947                 </p>
1948               </dd>
1949               <dt>
1950                 Notes:
1951               </dt>
1952               <dd>
1953                 <p>
1954                   This action is only concerned with <span class=
1955                   "emphasis"><i class="EMPHASIS">incoming</i></span> HTTP
1956                   cookies. For <span class="emphasis"><i class=
1957                   "EMPHASIS">outgoing</i></span> HTTP cookies, use <tt class=
1958                   "LITERAL"><a href=
1959                   "actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a></tt>.
1960                   Use <span class="emphasis"><i class=
1961                   "EMPHASIS">both</i></span> to disable HTTP cookies
1962                   completely.
1963                 </p>
1964                 <p>
1965                   It makes <span class="emphasis"><i class="EMPHASIS">no
1966                   sense at all</i></span> to use this action in conjunction
1967                   with the <tt class="LITERAL"><a href=
1968                   "actions-file.html#SESSION-COOKIES-ONLY">session-cookies-only</a></tt>
1969                   action, since it would prevent the session cookies from
1970                   being set. See also <tt class="LITERAL"><a href=
1971                   "actions-file.html#FILTER-CONTENT-COOKIES">filter-content-cookies</a></tt>.
1972                 </p>
1973               </dd>
1974               <dt>
1975                 Example usage:
1976               </dt>
1977               <dd>
1978                 <p>
1979                 </p>
1980                 <table border="0" bgcolor="#E0E0E0" width="90%">
1981                   <tr>
1982                     <td>
1983 <pre class="SCREEN">
1984 +crunch-incoming-cookies
1985 </pre>
1986                     </td>
1987                   </tr>
1988                 </table>
1989               </dd>
1990             </dl>
1991           </div>
1992         </div>
1993         <div class="SECT3">
1994           <h4 class="SECT3">
1995             <a name="CRUNCH-SERVER-HEADER">8.5.10. crunch-server-header</a>
1996           </h4>
1997           <div class="VARIABLELIST">
1998             <dl>
1999               <dt>
2000                 Typical use:
2001               </dt>
2002               <dd>
2003                 <p>
2004                   Remove a server header <span class=
2005                   "APPLICATION">Privoxy</span> has no dedicated action for.
2006                 </p>
2007               </dd>
2008               <dt>
2009                 Effect:
2010               </dt>
2011               <dd>
2012                 <p>
2013                   Deletes every header sent by the server that contains the
2014                   string the user supplied as parameter.
2015                 </p>
2016               </dd>
2017               <dt>
2018                 Type:
2019               </dt>
2020               <dd>
2021                 <p>
2022                   Parameterized.
2023                 </p>
2024               </dd>
2025               <dt>
2026                 Parameter:
2027               </dt>
2028               <dd>
2029                 <p>
2030                   Any string.
2031                 </p>
2032               </dd>
2033               <dt>
2034                 Notes:
2035               </dt>
2036               <dd>
2037                 <p>
2038                   This action allows you to block server headers for which no
2039                   dedicated <span class="APPLICATION">Privoxy</span> action
2040                   exists. <span class="APPLICATION">Privoxy</span> will
2041                   remove every server header that contains the string you
2042                   supplied as parameter.
2043                 </p>
2044                 <p>
2045                   Regular expressions are <span class="emphasis"><i class=
2046                   "EMPHASIS">not supported</i></span> and you can't use this
2047                   action to block different headers in the same request,
2048                   unless they contain the same string.
2049                 </p>
2050                 <p>
2051                   <tt class="LITERAL">crunch-server-header</tt> is only meant
2052                   for quick tests. If you have to block several different
2053                   headers, or only want to modify parts of them, you should
2054                   use a custom <tt class="LITERAL"><a href=
2055                   "actions-file.html#SERVER-HEADER-FILTER">server-header
2056                   filter</a></tt>.
2057                 </p>
2058                 <div class="WARNING">
2059                   <table class="WARNING" border="1" width="90%">
2060                     <tr>
2061                       <td align="CENTER">
2062                         <b>Warning</b>
2063                       </td>
2064                     </tr>
2065                     <tr>
2066                       <td align="LEFT">
2067                         <p>
2068                           Don't block any header without understanding the
2069                           consequences.
2070                         </p>
2071                       </td>
2072                     </tr>
2073                   </table>
2074                 </div>
2075               </dd>
2076               <dt>
2077                 Example usage (section):
2078               </dt>
2079               <dd>
2080                 <p>
2081                 </p>
2082                 <table border="0" bgcolor="#E0E0E0" width="90%">
2083                   <tr>
2084                     <td>
2085 <pre class="SCREEN">
2086 # Crunch server headers that try to prevent caching
2087 { +crunch-server-header{no-cache} }
2088 /
2089 </pre>
2090                     </td>
2091                   </tr>
2092                 </table>
2093               </dd>
2094             </dl>
2095           </div>
2096         </div>
2097         <div class="SECT3">
2098           <h4 class="SECT3">
2099             <a name="CRUNCH-OUTGOING-COOKIES">8.5.11.
2100             crunch-outgoing-cookies</a>
2101           </h4>
2102           <div class="VARIABLELIST">
2103             <dl>
2104               <dt>
2105                 Typical use:
2106               </dt>
2107               <dd>
2108                 <p>
2109                   Prevent the web server from reading any HTTP cookies from
2110                   your system
2111                 </p>
2112               </dd>
2113               <dt>
2114                 Effect:
2115               </dt>
2116               <dd>
2117                 <p>
2118                   Deletes any <span class="QUOTE">"Cookie:"</span> HTTP
2119                   headers from client requests.
2120                 </p>
2121               </dd>
2122               <dt>
2123                 Type:
2124               </dt>
2125               <dd>
2126                 <p>
2127                   Boolean.
2128                 </p>
2129               </dd>
2130               <dt>
2131                 Parameter:
2132               </dt>
2133               <dd>
2134                 <p>
2135                   N/A
2136                 </p>
2137               </dd>
2138               <dt>
2139                 Notes:
2140               </dt>
2141               <dd>
2142                 <p>
2143                   This action is only concerned with <span class=
2144                   "emphasis"><i class="EMPHASIS">outgoing</i></span> HTTP
2145                   cookies. For <span class="emphasis"><i class=
2146                   "EMPHASIS">incoming</i></span> HTTP cookies, use <tt class=
2147                   "LITERAL"><a href=
2148                   "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a></tt>.
2149                   Use <span class="emphasis"><i class=
2150                   "EMPHASIS">both</i></span> to disable HTTP cookies
2151                   completely.
2152                 </p>
2153                 <p>
2154                   It makes <span class="emphasis"><i class="EMPHASIS">no
2155                   sense at all</i></span> to use this action in conjunction
2156                   with the <tt class="LITERAL"><a href=
2157                   "actions-file.html#SESSION-COOKIES-ONLY">session-cookies-only</a></tt>
2158                   action, since it would prevent the session cookies from
2159                   being read.
2160                 </p>
2161               </dd>
2162               <dt>
2163                 Example usage:
2164               </dt>
2165               <dd>
2166                 <p>
2167                 </p>
2168                 <table border="0" bgcolor="#E0E0E0" width="90%">
2169                   <tr>
2170                     <td>
2171 <pre class="SCREEN">
2172 +crunch-outgoing-cookies
2173 </pre>
2174                     </td>
2175                   </tr>
2176                 </table>
2177               </dd>
2178             </dl>
2179           </div>
2180         </div>
2181         <div class="SECT3">
2182           <h4 class="SECT3">
2183             <a name="DEANIMATE-GIFS">8.5.12. deanimate-gifs</a>
2184           </h4>
2185           <div class="VARIABLELIST">
2186             <dl>
2187               <dt>
2188                 Typical use:
2189               </dt>
2190               <dd>
2191                 <p>
2192                   Stop those annoying, distracting animated GIF images.
2193                 </p>
2194               </dd>
2195               <dt>
2196                 Effect:
2197               </dt>
2198               <dd>
2199                 <p>
2200                   De-animate GIF animations, i.e. reduce them to their first
2201                   or last image.
2202                 </p>
2203               </dd>
2204               <dt>
2205                 Type:
2206               </dt>
2207               <dd>
2208                 <p>
2209                   Parameterized.
2210                 </p>
2211               </dd>
2212               <dt>
2213                 Parameter:
2214               </dt>
2215               <dd>
2216                 <p>
2217                   <span class="QUOTE">"last"</span> or <span class=
2218                   "QUOTE">"first"</span>
2219                 </p>
2220               </dd>
2221               <dt>
2222                 Notes:
2223               </dt>
2224               <dd>
2225                 <p>
2226                   This will also shrink the images considerably (in bytes,
2227                   not pixels!). If the option <span class=
2228                   "QUOTE">"first"</span> is given, the first frame of the
2229                   animation is used as the replacement. If <span class=
2230                   "QUOTE">"last"</span> is given, the last frame of the
2231                   animation is used instead, which probably makes more sense
2232                   for most banner animations, but also has the risk of not
2233                   showing the entire last frame (if it is only a delta to an
2234                   earlier frame).
2235                 </p>
2236                 <p>
2237                   You can safely use this action with patterns that will also
2238                   match non-GIF objects, because no attempt will be made at
2239                   anything that doesn't look like a GIF.
2240                 </p>
2241               </dd>
2242               <dt>
2243                 Example usage:
2244               </dt>
2245               <dd>
2246                 <p>
2247                 </p>
2248                 <table border="0" bgcolor="#E0E0E0" width="90%">
2249                   <tr>
2250                     <td>
2251 <pre class="SCREEN">
2252 +deanimate-gifs{last}
2253 </pre>
2254                     </td>
2255                   </tr>
2256                 </table>
2257               </dd>
2258             </dl>
2259           </div>
2260         </div>
2261         <div class="SECT3">
2262           <h4 class="SECT3">
2263             <a name="DOWNGRADE-HTTP-VERSION">8.5.13.
2264             downgrade-http-version</a>
2265           </h4>
2266           <div class="VARIABLELIST">
2267             <dl>
2268               <dt>
2269                 Typical use:
2270               </dt>
2271               <dd>
2272                 <p>
2273                   Work around (very rare) problems with HTTP/1.1
2274                 </p>
2275               </dd>
2276               <dt>
2277                 Effect:
2278               </dt>
2279               <dd>
2280                 <p>
2281                   Downgrades HTTP/1.1 client requests and server replies to
2282                   HTTP/1.0.
2283                 </p>
2284               </dd>
2285               <dt>
2286                 Type:
2287               </dt>
2288               <dd>
2289                 <p>
2290                   Boolean.
2291                 </p>
2292               </dd>
2293               <dt>
2294                 Parameter:
2295               </dt>
2296               <dd>
2297                 <p>
2298                   N/A
2299                 </p>
2300               </dd>
2301               <dt>
2302                 Notes:
2303               </dt>
2304               <dd>
2305                 <p>
2306                   This is a left-over from the time when <span class=
2307                   "APPLICATION">Privoxy</span> didn't support important
2308                   HTTP/1.1 features well. It is left here for the unlikely
2309                   case that you experience HTTP/1.1 related problems with
2310                   some server out there. Not all HTTP/1.1 features and
2311                   requirements are supported yet, so there is a chance you
2312                   might need this action.
2313                 </p>
2314               </dd>
2315               <dt>
2316                 Example usage (section):
2317               </dt>
2318               <dd>
2319                 <p>
2320                 </p>
2321                 <table border="0" bgcolor="#E0E0E0" width="90%">
2322                   <tr>
2323                     <td>
2324 <pre class="SCREEN">
2325 {+downgrade-http-version}
2326 problem-host.example.com
2327 </pre>
2328                     </td>
2329                   </tr>
2330                 </table>
2331               </dd>
2332             </dl>
2333           </div>
2334         </div>
2335         <div class="SECT3">
2336           <h4 class="SECT3">
2337             <a name="FAST-REDIRECTS">8.5.14. fast-redirects</a>
2338           </h4>
2339           <div class="VARIABLELIST">
2340             <dl>
2341               <dt>
2342                 Typical use:
2343               </dt>
2344               <dd>
2345                 <p>
2346                   Fool some click-tracking scripts and speed up indirect
2347                   links.
2348                 </p>
2349               </dd>
2350               <dt>
2351                 Effect:
2352               </dt>
2353               <dd>
2354                 <p>
2355                   Detects redirection URLs and redirects the browser without
2356                   contacting the redirection server first.
2357                 </p>
2358               </dd>
2359               <dt>
2360                 Type:
2361               </dt>
2362               <dd>
2363                 <p>
2364                   Parameterized.
2365                 </p>
2366               </dd>
2367               <dt>
2368                 Parameter:
2369               </dt>
2370               <dd>
2371                 <ul>
2372                   <li>
2373                     <p>
2374                       <span class="QUOTE">"simple-check"</span> to just
2375                       search for the string <span class=
2376                       "QUOTE">"http://"</span> to detect redirection URLs.
2377                     </p>
2378                   </li>
2379                   <li>
2380                     <p>
2381                       <span class="QUOTE">"check-decoded-url"</span> to
2382                       decode URLs (if necessary) before searching for
2383                       redirection URLs.
2384                     </p>
2385                   </li>
2386                 </ul>
2387               </dd>
2388               <dt>
2389                 Notes:
2390               </dt>
2391               <dd>
2392                 <p>
2393                   Many sites, like yahoo.com, don't just link to other sites.
2394                   Instead, they will link to some script on their own
2395                   servers, giving the destination as a parameter, which will
2396                   then redirect you to the final target. URLs resulting from
2397                   this scheme typically look like: <span class=
2398                   "QUOTE">"http://www.example.org/click-tracker.cgi?target=http%3a//www.example.net/"</span>.
2399                 </p>
2400                 <p>
2401                   Sometimes, there are even multiple consecutive redirects
2402                   encoded in the URL. These redirections via scripts make
2403                   your web browsing more traceable, since the server from
2404                   which you follow such a link can see where you go to. Apart
2405                   from that, valuable bandwidth and time is wasted, while
2406                   your browser asks the server for one redirect after the
2407                   other. Plus, it feeds the advertisers.
2408                 </p>
2409                 <p>
2410                   This feature is currently not very smart and is scheduled
2411                   for improvement. If it is enabled by default, you will have
2412                   to create some exceptions to this action. It can lead to
2413                   failures in several ways:
2414                 </p>
2415                 <p>
2416                   Not every URLs with other URLs as parameters is evil. Some
2417                   sites offer a real service that requires this information
2418                   to work. For example a validation service needs to know,
2419                   which document to validate. <tt class=
2420                   "LITERAL">fast-redirects</tt> assumes that every URL
2421                   parameter that looks like another URL is a redirection
2422                   target, and will always redirect to the last one. Most of
2423                   the time the assumption is correct, but if it isn't, the
2424                   user gets redirected anyway.
2425                 </p>
2426                 <p>
2427                   Another failure occurs if the URL contains other parameters
2428                   after the URL parameter. The URL: <span class=
2429                   "QUOTE">"http://www.example.org/?redirect=http%3a//www.example.net/&amp;foo=bar"</span>.
2430                   contains the redirection URL <span class=
2431                   "QUOTE">"http://www.example.net/"</span>, followed by
2432                   another parameter. <tt class="LITERAL">fast-redirects</tt>
2433                   doesn't know that and will cause a redirect to <span class=
2434                   "QUOTE">"http://www.example.net/&amp;foo=bar"</span>.
2435                   Depending on the target server configuration, the parameter
2436                   will be silently ignored or lead to a <span class=
2437                   "QUOTE">"page not found"</span> error. You can prevent this
2438                   problem by first using the <tt class="LITERAL"><a href=
2439                   "actions-file.html#REDIRECT">redirect</a></tt> action to
2440                   remove the last part of the URL, but it requires a little
2441                   effort.
2442                 </p>
2443                 <p>
2444                   To detect a redirection URL, <tt class=
2445                   "LITERAL">fast-redirects</tt> only looks for the string
2446                   <span class="QUOTE">"http://"</span>, either in plain text
2447                   (invalid but often used) or encoded as <span class=
2448                   "QUOTE">"http%3a//"</span>. Some sites use their own URL
2449                   encoding scheme, encrypt the address of the target server
2450                   or replace it with a database id. In theses cases <tt
2451                   class="LITERAL">fast-redirects</tt> is fooled and the
2452                   request reaches the redirection server where it probably
2453                   gets logged.
2454                 </p>
2455               </dd>
2456               <dt>
2457                 Example usage:
2458               </dt>
2459               <dd>
2460                 <p>
2461                 </p>
2462                 <table border="0" bgcolor="#E0E0E0" width="90%">
2463                   <tr>
2464                     <td>
2465 <pre class="SCREEN">
2466  { +fast-redirects{simple-check} }
2467    one.example.com
2468
2469  { +fast-redirects{check-decoded-url} }
2470    another.example.com/testing
2471 </pre>
2472                     </td>
2473                   </tr>
2474                 </table>
2475               </dd>
2476             </dl>
2477           </div>
2478         </div>
2479         <div class="SECT3">
2480           <h4 class="SECT3">
2481             <a name="FILTER">8.5.15. filter</a>
2482           </h4>
2483           <div class="VARIABLELIST">
2484             <dl>
2485               <dt>
2486                 Typical use:
2487               </dt>
2488               <dd>
2489                 <p>
2490                   Get rid of HTML and JavaScript annoyances, banner
2491                   advertisements (by size), do fun text replacements, add
2492                   personalized effects, etc.
2493                 </p>
2494               </dd>
2495               <dt>
2496                 Effect:
2497               </dt>
2498               <dd>
2499                 <p>
2500                   All instances of text-based type, most notably HTML and
2501                   JavaScript, to which this action applies, can be filtered
2502                   on-the-fly through the specified regular expression based
2503                   substitutions. (Note: as of version 3.0.3 plain text
2504                   documents are exempted from filtering, because web servers
2505                   often use the <tt class="LITERAL">text/plain</tt> MIME type
2506                   for all files whose type they don't know.)
2507                 </p>
2508               </dd>
2509               <dt>
2510                 Type:
2511               </dt>
2512               <dd>
2513                 <p>
2514                   Parameterized.
2515                 </p>
2516               </dd>
2517               <dt>
2518                 Parameter:
2519               </dt>
2520               <dd>
2521                 <p>
2522                   The name of a content filter, as defined in the <a href=
2523                   "filter-file.html">filter file</a>. Filters can be defined
2524                   in one or more files as defined by the <tt class=
2525                   "LITERAL"><a href=
2526                   "config.html#FILTERFILE">filterfile</a></tt> option in the
2527                   <a href="config.html">config file</a>. <tt class=
2528                   "FILENAME">default.filter</tt> is the collection of filters
2529                   supplied by the developers. Locally defined filters should
2530                   go in their own file, such as <tt class=
2531                   "FILENAME">user.filter</tt>.
2532                 </p>
2533                 <p>
2534                   When used in its negative form, and without parameters,
2535                   <span class="emphasis"><i class="EMPHASIS">all</i></span>
2536                   filtering is completely disabled.
2537                 </p>
2538               </dd>
2539               <dt>
2540                 Notes:
2541               </dt>
2542               <dd>
2543                 <p>
2544                   For your convenience, there are a number of pre-defined
2545                   filters available in the distribution filter file that you
2546                   can use. See the examples below for a list.
2547                 </p>
2548                 <p>
2549                   Filtering requires buffering the page content, which may
2550                   appear to slow down page rendering since nothing is
2551                   displayed until all content has passed the filters. (The
2552                   total time until the page is completely rendered doesn't
2553                   change much, but it may be perceived as slower since the
2554                   page is not incrementally displayed.) This effect will be
2555                   more noticeable on slower connections.
2556                 </p>
2557                 <p>
2558                   <span class="QUOTE">"Rolling your own"</span> filters
2559                   requires a knowledge of <a href=
2560                   "http://en.wikipedia.org/wiki/Regular_expressions" target=
2561                   "_top"><span class="QUOTE">"Regular Expressions"</span></a>
2562                   and <a href="http://en.wikipedia.org/wiki/Html" target=
2563                   "_top"><span class="QUOTE">"HTML"</span></a>. This is very
2564                   powerful feature, and potentially very intrusive. Filters
2565                   should be used with caution, and where an equivalent <span
2566                   class="QUOTE">"action"</span> is not available.
2567                 </p>
2568                 <p>
2569                   The amount of data that can be filtered is limited to the
2570                   <tt class="LITERAL"><a href=
2571                   "config.html#BUFFER-LIMIT">buffer-limit</a></tt> option in
2572                   the main <a href="config.html">config file</a>. The default
2573                   is 4096 KB (4 Megs). Once this limit is exceeded, the
2574                   buffered data, and all pending data, is passed through
2575                   unfiltered.
2576                 </p>
2577                 <p>
2578                   Inappropriate MIME types, such as zipped files, are not
2579                   filtered at all. (Again, only text-based types except plain
2580                   text). Encrypted SSL data (from HTTPS servers) cannot be
2581                   filtered either, since this would violate the integrity of
2582                   the secure transaction. In some situations it might be
2583                   necessary to protect certain text, like source code, from
2584                   filtering by defining appropriate <tt class=
2585                   "LITERAL">-filter</tt> exceptions.
2586                 </p>
2587                 <p>
2588                   Compressed content can't be filtered either, unless <span
2589                   class="APPLICATION">Privoxy</span> is compiled with zlib
2590                   support (requires at least <span class=
2591                   "APPLICATION">Privoxy</span> 3.0.7), in which case <span
2592                   class="APPLICATION">Privoxy</span> will decompress the
2593                   content before filtering it.
2594                 </p>
2595                 <p>
2596                   If you use a <span class="APPLICATION">Privoxy</span>
2597                   version without zlib support, but want filtering to work on
2598                   as much documents as possible, even those that would
2599                   normally be sent compressed, you must use the <tt class=
2600                   "LITERAL"><a href=
2601                   "actions-file.html#PREVENT-COMPRESSION">prevent-compression</a></tt>
2602                   action in conjunction with <tt class="LITERAL">filter</tt>.
2603                 </p>
2604                 <p>
2605                   Content filtering can achieve some of the same effects as
2606                   the <tt class="LITERAL"><a href=
2607                   "actions-file.html#BLOCK">block</a></tt> action, i.e. it
2608                   can be used to block ads and banners. But the mechanism
2609                   works quite differently. One effective use, is to block ad
2610                   banners based on their size (see below), since many of
2611                   these seem to be somewhat standardized.
2612                 </p>
2613                 <p>
2614                   <a href="contact.html">Feedback</a> with suggestions for
2615                   new or improved filters is particularly welcome!
2616                 </p>
2617                 <p>
2618                   The below list has only the names and a one-line
2619                   description of each predefined filter. There are <a href=
2620                   "filter-file.html#PREDEFINED-FILTERS">more verbose
2621                   explanations</a> of what these filters do in the <a href=
2622                   "filter-file.html">filter file chapter</a>.
2623                 </p>
2624               </dd>
2625               <dt>
2626                 Example usage (with filters from the distribution <tt class=
2627                 "FILENAME">default.filter</tt> file). See <a href=
2628                 "filter-file.html#PREDEFINED-FILTERS">the Predefined Filters
2629                 section</a> for more explanation on each:
2630               </dt>
2631               <dd>
2632                 <p>
2633                   <a name="FILTER-JS-ANNOYANCES"></a>
2634                 </p>
2635                 <table border="0" bgcolor="#E0E0E0" width="90%">
2636                   <tr>
2637                     <td>
2638 <pre class="SCREEN">
2639 +filter{js-annoyances}       # Get rid of particularly annoying JavaScript abuse.
2640 </pre>
2641                     </td>
2642                   </tr>
2643                 </table>
2644
2645                 <p>
2646                   <a name="FILTER-JS-EVENTS"></a>
2647                 </p>
2648                 <table border="0" bgcolor="#E0E0E0" width="90%">
2649                   <tr>
2650                     <td>
2651 <pre class="SCREEN">
2652 +filter{js-events}           # Kill all JS event bindings and timers (Radically destructive! Only for extra nasty sites).
2653 </pre>
2654                     </td>
2655                   </tr>
2656                 </table>
2657
2658                 <p>
2659                   <a name="FILTER-HTML-ANNOYANCES"></a>
2660                 </p>
2661                 <table border="0" bgcolor="#E0E0E0" width="90%">
2662                   <tr>
2663                     <td>
2664 <pre class="SCREEN">
2665 +filter{html-annoyances}     # Get rid of particularly annoying HTML abuse.
2666 </pre>
2667                     </td>
2668                   </tr>
2669                 </table>
2670
2671                 <p>
2672                   <a name="FILTER-CONTENT-COOKIES"></a>
2673                 </p>
2674                 <table border="0" bgcolor="#E0E0E0" width="90%">
2675                   <tr>
2676                     <td>
2677 <pre class="SCREEN">
2678 +filter{content-cookies}     # Kill cookies that come in the HTML or JS content.
2679 </pre>
2680                     </td>
2681                   </tr>
2682                 </table>
2683
2684                 <p>
2685                   <a name="FILTER-REFRESH-TAGS"></a>
2686                 </p>
2687                 <table border="0" bgcolor="#E0E0E0" width="90%">
2688                   <tr>
2689                     <td>
2690 <pre class="SCREEN">
2691 +filter{refresh-tags}        # Kill automatic refresh tags (for dial-on-demand setups).
2692 </pre>
2693                     </td>
2694                   </tr>
2695                 </table>
2696
2697                 <p>
2698                   <a name="FILTER-UNSOLICITED-POPUPS"></a>
2699                 </p>
2700                 <table border="0" bgcolor="#E0E0E0" width="90%">
2701                   <tr>
2702                     <td>
2703 <pre class="SCREEN">
2704 +filter{unsolicited-popups}  # Disable only unsolicited pop-up windows. Useful if your browser lacks this ability.
2705 </pre>
2706                     </td>
2707                   </tr>
2708                 </table>
2709
2710                 <p>
2711                   <a name="FILTER-ALL-POPUPS"></a>
2712                 </p>
2713                 <table border="0" bgcolor="#E0E0E0" width="90%">
2714                   <tr>
2715                     <td>
2716 <pre class="SCREEN">
2717 +filter{all-popups}          # Kill all popups in JavaScript and HTML. Useful if your browser lacks this ability.
2718 </pre>
2719                     </td>
2720                   </tr>
2721                 </table>
2722
2723                 <p>
2724                   <a name="FILTER-IMG-REORDER"></a>
2725                 </p>
2726                 <table border="0" bgcolor="#E0E0E0" width="90%">
2727                   <tr>
2728                     <td>
2729 <pre class="SCREEN">
2730 +filter{img-reorder}         # Reorder attributes in &lt;img&gt; tags to make the banners-by-* filters more effective.
2731 </pre>
2732                     </td>
2733                   </tr>
2734                 </table>
2735
2736                 <p>
2737                   <a name="FILTER-BANNERS-BY-SIZE"></a>
2738                 </p>
2739                 <table border="0" bgcolor="#E0E0E0" width="90%">
2740                   <tr>
2741                     <td>
2742 <pre class="SCREEN">
2743 +filter{banners-by-size}     # Kill banners by size.
2744 </pre>
2745                     </td>
2746                   </tr>
2747                 </table>
2748
2749                 <p>
2750                   <a name="FILTER-BANNERS-BY-LINK"></a>
2751                 </p>
2752                 <table border="0" bgcolor="#E0E0E0" width="90%">
2753                   <tr>
2754                     <td>
2755 <pre class="SCREEN">
2756 +filter{banners-by-link}     # Kill banners by their links to known clicktrackers.
2757 </pre>
2758                     </td>
2759                   </tr>
2760                 </table>
2761
2762                 <p>
2763                   <a name="FILTER-WEBBUGS"></a>
2764                 </p>
2765                 <table border="0" bgcolor="#E0E0E0" width="90%">
2766                   <tr>
2767                     <td>
2768 <pre class="SCREEN">
2769 +filter{webbugs}             # Squish WebBugs (1x1 invisible GIFs used for user tracking).
2770 </pre>
2771                     </td>
2772                   </tr>
2773                 </table>
2774
2775                 <p>
2776                   <a name="FILTER-TINY-TEXTFORMS"></a>
2777                 </p>
2778                 <table border="0" bgcolor="#E0E0E0" width="90%">
2779                   <tr>
2780                     <td>
2781 <pre class="SCREEN">
2782 +filter{tiny-textforms}      # Extend those tiny textareas up to 40x80 and kill the hard wrap.
2783 </pre>
2784                     </td>
2785                   </tr>
2786                 </table>
2787
2788                 <p>
2789                   <a name="FILTER-JUMPING-WINDOWS"></a>
2790                 </p>
2791                 <table border="0" bgcolor="#E0E0E0" width="90%">
2792                   <tr>
2793                     <td>
2794 <pre class="SCREEN">
2795 +filter{jumping-windows}     # Prevent windows from resizing and moving themselves.
2796 </pre>
2797                     </td>
2798                   </tr>
2799                 </table>
2800
2801                 <p>
2802                   <a name="FILTER-FRAMESET-BORDERS"></a>
2803                 </p>
2804                 <table border="0" bgcolor="#E0E0E0" width="90%">
2805                   <tr>
2806                     <td>
2807 <pre class="SCREEN">
2808 +filter{frameset-borders}    # Give frames a border and make them resizable.
2809 </pre>
2810                     </td>
2811                   </tr>
2812                 </table>
2813
2814                 <p>
2815                   <a name="FILTER-DEMORONIZER"></a>
2816                 </p>
2817                 <table border="0" bgcolor="#E0E0E0" width="90%">
2818                   <tr>
2819                     <td>
2820 <pre class="SCREEN">
2821 +filter{demoronizer}         # Fix MS's non-standard use of standard charsets.
2822 </pre>
2823                     </td>
2824                   </tr>
2825                 </table>
2826
2827                 <p>
2828                   <a name="FILTER-SHOCKWAVE-FLASH"></a>
2829                 </p>
2830                 <table border="0" bgcolor="#E0E0E0" width="90%">
2831                   <tr>
2832                     <td>
2833 <pre class="SCREEN">
2834 +filter{shockwave-flash}     # Kill embedded Shockwave Flash objects.
2835 </pre>
2836                     </td>
2837                   </tr>
2838                 </table>
2839
2840                 <p>
2841                   <a name="FILTER-QUICKTIME-KIOSKMODE"></a>
2842                 </p>
2843                 <table border="0" bgcolor="#E0E0E0" width="90%">
2844                   <tr>
2845                     <td>
2846 <pre class="SCREEN">
2847 +filter{quicktime-kioskmode} # Make Quicktime movies saveable.
2848 </pre>
2849                     </td>
2850                   </tr>
2851                 </table>
2852
2853                 <p>
2854                   <a name="FILTER-FUN"></a>
2855                 </p>
2856                 <table border="0" bgcolor="#E0E0E0" width="90%">
2857                   <tr>
2858                     <td>
2859 <pre class="SCREEN">
2860 +filter{fun}                 # Text replacements for subversive browsing fun!
2861 </pre>
2862                     </td>
2863                   </tr>
2864                 </table>
2865
2866                 <p>
2867                   <a name="FILTER-CRUDE-PARENTAL"></a>
2868                 </p>
2869                 <table border="0" bgcolor="#E0E0E0" width="90%">
2870                   <tr>
2871                     <td>
2872 <pre class="SCREEN">
2873 +filter{crude-parental}      # Crude parental filtering. Note that this filter doesn't work reliably.
2874 </pre>
2875                     </td>
2876                   </tr>
2877                 </table>
2878
2879                 <p>
2880                   <a name="FILTER-IE-EXPLOITS"></a>
2881                 </p>
2882                 <table border="0" bgcolor="#E0E0E0" width="90%">
2883                   <tr>
2884                     <td>
2885 <pre class="SCREEN">
2886 +filter{ie-exploits}         # Disable some known Internet Explorer bug exploits.
2887 </pre>
2888                     </td>
2889                   </tr>
2890                 </table>
2891
2892                 <p>
2893                   <a name="FILTER-SITE-SPECIFICS"></a>
2894                 </p>
2895                 <table border="0" bgcolor="#E0E0E0" width="90%">
2896                   <tr>
2897                     <td>
2898 <pre class="SCREEN">
2899 +filter{site-specifics}      # Cure for site-specific problems. Don't apply generally!
2900 </pre>
2901                     </td>
2902                   </tr>
2903                 </table>
2904
2905                 <p>
2906                   <a name="FILTER-NO-PING"></a>
2907                 </p>
2908                 <table border="0" bgcolor="#E0E0E0" width="90%">
2909                   <tr>
2910                     <td>
2911 <pre class="SCREEN">
2912 +filter{no-ping}             # Removes non-standard ping attributes in &lt;a&gt; and &lt;area&gt; tags.
2913 </pre>
2914                     </td>
2915                   </tr>
2916                 </table>
2917
2918                 <p>
2919                   <a name="FILTER-GOOGLE"></a>
2920                 </p>
2921                 <table border="0" bgcolor="#E0E0E0" width="90%">
2922                   <tr>
2923                     <td>
2924 <pre class="SCREEN">
2925 +filter{google}              # CSS-based block for Google text ads. Also removes a width limitation and the toolbar advertisement.
2926 </pre>
2927                     </td>
2928                   </tr>
2929                 </table>
2930
2931                 <p>
2932                   <a name="FILTER-YAHOO"></a>
2933                 </p>
2934                 <table border="0" bgcolor="#E0E0E0" width="90%">
2935                   <tr>
2936                     <td>
2937 <pre class="SCREEN">
2938 +filter{yahoo}               # CSS-based block for Yahoo text ads. Also removes a width limitation.
2939 </pre>
2940                     </td>
2941                   </tr>
2942                 </table>
2943
2944                 <p>
2945                   <a name="FILTER-MSN"></a>
2946                 </p>
2947                 <table border="0" bgcolor="#E0E0E0" width="90%">
2948                   <tr>
2949                     <td>
2950 <pre class="SCREEN">
2951 +filter{msn}                 # CSS-based block for MSN text ads. Also removes tracking URLs and a width limitation.
2952 </pre>
2953                     </td>
2954                   </tr>
2955                 </table>
2956
2957                 <p>
2958                   <a name="FILTER-BLOGSPOT"></a>
2959                 </p>
2960                 <table border="0" bgcolor="#E0E0E0" width="90%">
2961                   <tr>
2962                     <td>
2963 <pre class="SCREEN">
2964 +filter{blogspot}            # Cleans up some Blogspot blogs. Read the fine print before using this.
2965 </pre>
2966                     </td>
2967                   </tr>
2968                 </table>
2969               </dd>
2970             </dl>
2971           </div>
2972         </div>
2973         <div class="SECT3">
2974           <h4 class="SECT3">
2975             <a name="FORCE-TEXT-MODE">8.5.16. force-text-mode</a>
2976           </h4>
2977           <div class="VARIABLELIST">
2978             <dl>
2979               <dt>
2980                 Typical use:
2981               </dt>
2982               <dd>
2983                 <p>
2984                   Force <span class="APPLICATION">Privoxy</span> to treat a
2985                   document as if it was in some kind of <span class=
2986                   "emphasis"><i class="EMPHASIS">text</i></span> format.
2987                 </p>
2988               </dd>
2989               <dt>
2990                 Effect:
2991               </dt>
2992               <dd>
2993                 <p>
2994                   Declares a document as text, even if the <span class=
2995                   "QUOTE">"Content-Type:"</span> isn't detected as such.
2996                 </p>
2997               </dd>
2998               <dt>
2999                 Type:
3000               </dt>
3001               <dd>
3002                 <p>
3003                   Boolean.
3004                 </p>
3005               </dd>
3006               <dt>
3007                 Parameter:
3008               </dt>
3009               <dd>
3010                 <p>
3011                   N/A
3012                 </p>
3013               </dd>
3014               <dt>
3015                 Notes:
3016               </dt>
3017               <dd>
3018                 <p>
3019                   As explained <tt class="LITERAL"><a href=
3020                   "actions-file.html#FILTER">above</a></tt>, <span class=
3021                   "APPLICATION">Privoxy</span> tries to only filter files
3022                   that are in some kind of text format. The same restrictions
3023                   apply to <tt class="LITERAL"><a href=
3024                   "actions-file.html#CONTENT-TYPE-OVERWRITE">content-type-overwrite</a></tt>.
3025                   <tt class="LITERAL">force-text-mode</tt> declares a
3026                   document as text, without looking at the <span class=
3027                   "QUOTE">"Content-Type:"</span> first.
3028                 </p>
3029                 <div class="WARNING">
3030                   <table class="WARNING" border="1" width="90%">
3031                     <tr>
3032                       <td align="CENTER">
3033                         <b>Warning</b>
3034                       </td>
3035                     </tr>
3036                     <tr>
3037                       <td align="LEFT">
3038                         <p>
3039                           Think twice before activating this action.
3040                           Filtering binary data with regular expressions can
3041                           cause file damage.
3042                         </p>
3043                       </td>
3044                     </tr>
3045                   </table>
3046                 </div>
3047               </dd>
3048               <dt>
3049                 Example usage:
3050               </dt>
3051               <dd>
3052                 <p>
3053                 </p>
3054                 <table border="0" bgcolor="#E0E0E0" width="90%">
3055                   <tr>
3056                     <td>
3057 <pre class="SCREEN">
3058 +force-text-mode
3059
3060 </pre>
3061                     </td>
3062                   </tr>
3063                 </table>
3064               </dd>
3065             </dl>
3066           </div>
3067         </div>
3068         <div class="SECT3">
3069           <h4 class="SECT3">
3070             <a name="FORWARD-OVERRIDE">8.5.17. forward-override</a>
3071           </h4>
3072           <div class="VARIABLELIST">
3073             <dl>
3074               <dt>
3075                 Typical use:
3076               </dt>
3077               <dd>
3078                 <p>
3079                   Change the forwarding settings based on User-Agent or
3080                   request origin
3081                 </p>
3082               </dd>
3083               <dt>
3084                 Effect:
3085               </dt>
3086               <dd>
3087                 <p>
3088                   Overrules the forward directives in the configuration file.
3089                 </p>
3090               </dd>
3091               <dt>
3092                 Type:
3093               </dt>
3094               <dd>
3095                 <p>
3096                   Multi-value.
3097                 </p>
3098               </dd>
3099               <dt>
3100                 Parameter:
3101               </dt>
3102               <dd>
3103                 <ul>
3104                   <li>
3105                     <p>
3106                       <span class="QUOTE">"forward ."</span> to use a direct
3107                       connection without any additional proxies.
3108                     </p>
3109                   </li>
3110                   <li>
3111                     <p>
3112                       <span class="QUOTE">"forward 127.0.0.1:8123"</span> to
3113                       use the HTTP proxy listening at 127.0.0.1 port 8123.
3114                     </p>
3115                   </li>
3116                   <li>
3117                     <p>
3118                       <span class="QUOTE">"forward-socks4a 127.0.0.1:9050
3119                       ."</span> to use the socks4a proxy listening at
3120                       127.0.0.1 port 9050. Replace <span class=
3121                       "QUOTE">"forward-socks4a"</span> with <span class=
3122                       "QUOTE">"forward-socks4"</span> to use a socks4
3123                       connection (with local DNS resolution) instead, use
3124                       <span class="QUOTE">"forward-socks5"</span> for socks5
3125                       connections (with remote DNS resolution).
3126                     </p>
3127                   </li>
3128                   <li>
3129                     <p>
3130                       <span class="QUOTE">"forward-socks4a 127.0.0.1:9050
3131                       proxy.example.org:8000"</span> to use the socks4a proxy
3132                       listening at 127.0.0.1 port 9050 to reach the HTTP
3133                       proxy listening at proxy.example.org port 8000. Replace
3134                       <span class="QUOTE">"forward-socks4a"</span> with <span
3135                       class="QUOTE">"forward-socks4"</span> to use a socks4
3136                       connection (with local DNS resolution) instead, use
3137                       <span class="QUOTE">"forward-socks5"</span> for socks5
3138                       connections (with remote DNS resolution).
3139                     </p>
3140                   </li>
3141                 </ul>
3142               </dd>
3143               <dt>
3144                 Notes:
3145               </dt>
3146               <dd>
3147                 <p>
3148                   This action takes parameters similar to the <a href=
3149                   "config.html#FORWARDING">forward</a> directives in the
3150                   configuration file, but without the URL pattern. It can be
3151                   used as replacement, but normally it's only used in cases
3152                   where matching based on the request URL isn't sufficient.
3153                 </p>
3154                 <div class="WARNING">
3155                   <table class="WARNING" border="1" width="90%">
3156                     <tr>
3157                       <td align="CENTER">
3158                         <b>Warning</b>
3159                       </td>
3160                     </tr>
3161                     <tr>
3162                       <td align="LEFT">
3163                         <p>
3164                           Please read the description for the <a href=
3165                           "config.html#FORWARDING">forward</a> directives
3166                           before using this action. Forwarding to the wrong
3167                           people will reduce your privacy and increase the
3168                           chances of man-in-the-middle attacks.
3169                         </p>
3170                         <p>
3171                           If the ports are missing or invalid, default values
3172                           will be used. This might change in the future and
3173                           you shouldn't rely on it. Otherwise incorrect
3174                           syntax causes Privoxy to exit.
3175                         </p>
3176                         <p>
3177                           Use the <a href=
3178                           "http://config.privoxy.org/show-url-info" target=
3179                           "_top">show-url-info CGI page</a> to verify that
3180                           your forward settings do what you thought the do.
3181                         </p>
3182                       </td>
3183                     </tr>
3184                   </table>
3185                 </div>
3186               </dd>
3187               <dt>
3188                 Example usage:
3189               </dt>
3190               <dd>
3191                 <p>
3192                 </p>
3193                 <table border="0" bgcolor="#E0E0E0" width="90%">
3194                   <tr>
3195                     <td>
3196 <pre class="SCREEN">
3197 # Always use direct connections for requests previously tagged as
3198 # <span class="QUOTE">"User-Agent: fetch libfetch/2.0"</span> and make sure
3199 # resuming downloads continues to work.
3200 # This way you can continue to use Tor for your normal browsing,
3201 # without overloading the Tor network with your FreeBSD ports updates
3202 # or downloads of bigger files like ISOs.
3203 # Note that HTTP headers are easy to fake and therefore their
3204 # values are as (un)trustworthy as your clients and users.
3205 {+forward-override{forward .} \
3206  -hide-if-modified-since      \
3207  -overwrite-last-modified     \
3208 }
3209 TAG:^User-Agent: fetch libfetch/2\.0$
3210
3211 </pre>
3212                     </td>
3213                   </tr>
3214                 </table>
3215               </dd>
3216             </dl>
3217           </div>
3218         </div>
3219         <div class="SECT3">
3220           <h4 class="SECT3">
3221             <a name="HANDLE-AS-EMPTY-DOCUMENT">8.5.18.
3222             handle-as-empty-document</a>
3223           </h4>
3224           <div class="VARIABLELIST">
3225             <dl>
3226               <dt>
3227                 Typical use:
3228               </dt>
3229               <dd>
3230                 <p>
3231                   Mark URLs that should be replaced by empty documents <span
3232                   class="emphasis"><i class="EMPHASIS">if they get
3233                   blocked</i></span>
3234                 </p>
3235               </dd>
3236               <dt>
3237                 Effect:
3238               </dt>
3239               <dd>
3240                 <p>
3241                   This action alone doesn't do anything noticeable. It just
3242                   marks URLs. If the <tt class="LITERAL"><a href=
3243                   "actions-file.html#BLOCK">block</a></tt> action <span
3244                   class="emphasis"><i class="EMPHASIS">also
3245                   applies</i></span>, the presence or absence of this mark
3246                   decides whether an HTML <span class=
3247                   "QUOTE">"BLOCKED"</span> page, or an empty document will be
3248                   sent to the client as a substitute for the blocked content.
3249                   The <span class="emphasis"><i class=
3250                   "EMPHASIS">empty</i></span> document isn't literally empty,
3251                   but actually contains a single space.
3252                 </p>
3253               </dd>
3254               <dt>
3255                 Type:
3256               </dt>
3257               <dd>
3258                 <p>
3259                   Boolean.
3260                 </p>
3261               </dd>
3262               <dt>
3263                 Parameter:
3264               </dt>
3265               <dd>
3266                 <p>
3267                   N/A
3268                 </p>
3269               </dd>
3270               <dt>
3271                 Notes:
3272               </dt>
3273               <dd>
3274                 <p>
3275                   Some browsers complain about syntax errors if JavaScript
3276                   documents are blocked with <span class=
3277                   "APPLICATION">Privoxy's</span> default HTML page; this
3278                   option can be used to silence them. And of course this
3279                   action can also be used to eliminate the <span class=
3280                   "APPLICATION">Privoxy</span> BLOCKED message in frames.
3281                 </p>
3282                 <p>
3283                   The content type for the empty document can be specified
3284                   with <tt class="LITERAL"><a href=
3285                   "actions-file.html#CONTENT-TYPE-OVERWRITE">content-type-overwrite{}</a></tt>,
3286                   but usually this isn't necessary.
3287                 </p>
3288               </dd>
3289               <dt>
3290                 Example usage:
3291               </dt>
3292               <dd>
3293                 <p>
3294                 </p>
3295                 <table border="0" bgcolor="#E0E0E0" width="90%">
3296                   <tr>
3297                     <td>
3298 <pre class="SCREEN">
3299 # Block all documents on example.org that end with ".js",
3300 # but send an empty document instead of the usual HTML message.
3301 {+block{Blocked JavaScript} +handle-as-empty-document}
3302 example.org/.*\.js$
3303
3304 </pre>
3305                     </td>
3306                   </tr>
3307                 </table>
3308               </dd>
3309             </dl>
3310           </div>
3311         </div>
3312         <div class="SECT3">
3313           <h4 class="SECT3">
3314             <a name="HANDLE-AS-IMAGE">8.5.19. handle-as-image</a>
3315           </h4>
3316           <div class="VARIABLELIST">
3317             <dl>
3318               <dt>
3319                 Typical use:
3320               </dt>
3321               <dd>
3322                 <p>
3323                   Mark URLs as belonging to images (so they'll be replaced by
3324                   images <span class="emphasis"><i class="EMPHASIS">if they
3325                   do get blocked</i></span>, rather than HTML pages)
3326                 </p>
3327               </dd>
3328               <dt>
3329                 Effect:
3330               </dt>
3331               <dd>
3332                 <p>
3333                   This action alone doesn't do anything noticeable. It just
3334                   marks URLs as images. If the <tt class="LITERAL"><a href=
3335                   "actions-file.html#BLOCK">block</a></tt> action <span
3336                   class="emphasis"><i class="EMPHASIS">also
3337                   applies</i></span>, the presence or absence of this mark
3338                   decides whether an HTML <span class=
3339                   "QUOTE">"blocked"</span> page, or a replacement image (as
3340                   determined by the <tt class="LITERAL"><a href=
3341                   "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker</a></tt>
3342                   action) will be sent to the client as a substitute for the
3343                   blocked content.
3344                 </p>
3345               </dd>
3346               <dt>
3347                 Type:
3348               </dt>
3349               <dd>
3350                 <p>
3351                   Boolean.
3352                 </p>
3353               </dd>
3354               <dt>
3355                 Parameter:
3356               </dt>
3357               <dd>
3358                 <p>
3359                   N/A
3360                 </p>
3361               </dd>
3362               <dt>
3363                 Notes:
3364               </dt>
3365               <dd>
3366                 <p>
3367                   The below generic example section is actually part of <tt
3368                   class="FILENAME">default.action</tt>. It marks all URLs
3369                   with well-known image file name extensions as images and
3370                   should be left intact.
3371                 </p>
3372                 <p>
3373                   Users will probably only want to use the handle-as-image
3374                   action in conjunction with <tt class="LITERAL"><a href=
3375                   "actions-file.html#BLOCK">block</a></tt>, to block sources
3376                   of banners, whose URLs don't reflect the file type, like in
3377                   the second example section.
3378                 </p>
3379                 <p>
3380                   Note that you cannot treat HTML pages as images in most
3381                   cases. For instance, (in-line) ad frames require an HTML
3382                   page to be sent, or they won't display properly. Forcing
3383                   <tt class="LITERAL">handle-as-image</tt> in this situation
3384                   will not replace the ad frame with an image, but lead to
3385                   error messages.
3386                 </p>
3387               </dd>
3388               <dt>
3389                 Example usage (sections):
3390               </dt>
3391               <dd>
3392                 <p>
3393                 </p>
3394                 <table border="0" bgcolor="#E0E0E0" width="90%">
3395                   <tr>
3396                     <td>
3397 <pre class="SCREEN">
3398 # Generic image extensions:
3399 #
3400 {+handle-as-image}
3401 /.*\.(gif|jpg|jpeg|png|bmp|ico)$
3402
3403 # These don't look like images, but they're banners and should be
3404 # blocked as images:
3405 #
3406 {+block{Nasty banners.} +handle-as-image}
3407 nasty-banner-server.example.com/junk.cgi\?output=trash
3408 </pre>
3409                     </td>
3410                   </tr>
3411                 </table>
3412               </dd>
3413             </dl>
3414           </div>
3415         </div>
3416         <div class="SECT3">
3417           <h4 class="SECT3">
3418             <a name="HIDE-ACCEPT-LANGUAGE">8.5.20. hide-accept-language</a>
3419           </h4>
3420           <div class="VARIABLELIST">
3421             <dl>
3422               <dt>
3423                 Typical use:
3424               </dt>
3425               <dd>
3426                 <p>
3427                   Pretend to use different language settings.
3428                 </p>
3429               </dd>
3430               <dt>
3431                 Effect:
3432               </dt>
3433               <dd>
3434                 <p>
3435                   Deletes or replaces the <span class=
3436                   "QUOTE">"Accept-Language:"</span> HTTP header in client
3437                   requests.
3438                 </p>
3439               </dd>
3440               <dt>
3441                 Type:
3442               </dt>
3443               <dd>
3444                 <p>
3445                   Parameterized.
3446                 </p>
3447               </dd>
3448               <dt>
3449                 Parameter:
3450               </dt>
3451               <dd>
3452                 <p>
3453                   Keyword: <span class="QUOTE">"block"</span>, or any user
3454                   defined value.
3455                 </p>
3456               </dd>
3457               <dt>
3458                 Notes:
3459               </dt>
3460               <dd>
3461                 <p>
3462                   Faking the browser's language settings can be useful to
3463                   make a foreign User-Agent set with <tt class="LITERAL"><a
3464                   href=
3465                   "actions-file.html#HIDE-USER-AGENT">hide-user-agent</a></tt>
3466                   more believable.
3467                 </p>
3468                 <p>
3469                   However some sites with content in different languages
3470                   check the <span class="QUOTE">"Accept-Language:"</span> to
3471                   decide which one to take by default. Sometimes it isn't
3472                   possible to later switch to another language without
3473                   changing the <span class="QUOTE">"Accept-Language:"</span>
3474                   header first.
3475                 </p>
3476                 <p>
3477                   Therefore it's a good idea to either only change the <span
3478                   class="QUOTE">"Accept-Language:"</span> header to languages
3479                   you understand, or to languages that aren't wide spread.
3480                 </p>
3481                 <p>
3482                   Before setting the <span class=
3483                   "QUOTE">"Accept-Language:"</span> header to a rare
3484                   language, you should consider that it helps to make your
3485                   requests unique and thus easier to trace. If you don't plan
3486                   to change this header frequently, you should stick to a
3487                   common language.
3488                 </p>
3489               </dd>
3490               <dt>
3491                 Example usage (section):
3492               </dt>
3493               <dd>
3494                 <p>
3495                 </p>
3496                 <table border="0" bgcolor="#E0E0E0" width="90%">
3497                   <tr>
3498                     <td>
3499 <pre class="SCREEN">
3500 # Pretend to use Canadian language settings.
3501 {+hide-accept-language{en-ca} \
3502 +hide-user-agent{Mozilla/5.0 (X11; U; OpenBSD i386; en-CA; rv:1.8.0.4) Gecko/20060628 Firefox/1.5.0.4} \
3503 }
3504 /
3505 </pre>
3506                     </td>
3507                   </tr>
3508                 </table>
3509               </dd>
3510             </dl>
3511           </div>
3512         </div>
3513         <div class="SECT3">
3514           <h4 class="SECT3">
3515             <a name="HIDE-CONTENT-DISPOSITION">8.5.21.
3516             hide-content-disposition</a>
3517           </h4>
3518           <div class="VARIABLELIST">
3519             <dl>
3520               <dt>
3521                 Typical use:
3522               </dt>
3523               <dd>
3524                 <p>
3525                   Prevent download menus for content you prefer to view
3526                   inside the browser.
3527                 </p>
3528               </dd>
3529               <dt>
3530                 Effect:
3531               </dt>
3532               <dd>
3533                 <p>
3534                   Deletes or replaces the <span class=
3535                   "QUOTE">"Content-Disposition:"</span> HTTP header set by
3536                   some servers.
3537                 </p>
3538               </dd>
3539               <dt>
3540                 Type:
3541               </dt>
3542               <dd>
3543                 <p>
3544                   Parameterized.
3545                 </p>
3546               </dd>
3547               <dt>
3548                 Parameter:
3549               </dt>
3550               <dd>
3551                 <p>
3552                   Keyword: <span class="QUOTE">"block"</span>, or any user
3553                   defined value.
3554                 </p>
3555               </dd>
3556               <dt>
3557                 Notes:
3558               </dt>
3559               <dd>
3560                 <p>
3561                   Some servers set the <span class=
3562                   "QUOTE">"Content-Disposition:"</span> HTTP header for
3563                   documents they assume you want to save locally before
3564                   viewing them. The <span class=
3565                   "QUOTE">"Content-Disposition:"</span> header contains the
3566                   file name the browser is supposed to use by default.
3567                 </p>
3568                 <p>
3569                   In most browsers that understand this header, it makes it
3570                   impossible to <span class="emphasis"><i class=
3571                   "EMPHASIS">just view</i></span> the document, without
3572                   downloading it first, even if it's just a simple text file
3573                   or an image.
3574                 </p>
3575                 <p>
3576                   Removing the <span class=
3577                   "QUOTE">"Content-Disposition:"</span> header helps to
3578                   prevent this annoyance, but some browsers additionally
3579                   check the <span class="QUOTE">"Content-Type:"</span>
3580                   header, before they decide if they can display a document
3581                   without saving it first. In these cases, you have to change
3582                   this header as well, before the browser stops displaying
3583                   download menus.
3584                 </p>
3585                 <p>
3586                   It is also possible to change the server's file name
3587                   suggestion to another one, but in most cases it isn't worth
3588                   the time to set it up.
3589                 </p>
3590                 <p>
3591                   This action will probably be removed in the future, use
3592                   server-header filters instead.
3593                 </p>
3594               </dd>
3595               <dt>
3596                 Example usage:
3597               </dt>
3598               <dd>
3599                 <p>
3600                 </p>
3601                 <table border="0" bgcolor="#E0E0E0" width="90%">
3602                   <tr>
3603                     <td>
3604 <pre class="SCREEN">
3605 # Disarm the download link in Sourceforge's patch tracker
3606 { -filter \
3607  +content-type-overwrite{text/plain}\
3608  +hide-content-disposition{block} }
3609  .sourceforge.net/tracker/download\.php
3610 </pre>
3611                     </td>
3612                   </tr>
3613                 </table>
3614               </dd>
3615             </dl>
3616           </div>
3617         </div>
3618         <div class="SECT3">
3619           <h4 class="SECT3">
3620             <a name="HIDE-IF-MODIFIED-SINCE">8.5.22.
3621             hide-if-modified-since</a>
3622           </h4>
3623           <div class="VARIABLELIST">
3624             <dl>
3625               <dt>
3626                 Typical use:
3627               </dt>
3628               <dd>
3629                 <p>
3630                   Prevent yet another way to track the user's steps between
3631                   sessions.
3632                 </p>
3633               </dd>
3634               <dt>
3635                 Effect:
3636               </dt>
3637               <dd>
3638                 <p>
3639                   Deletes the <span class="QUOTE">"If-Modified-Since:"</span>
3640                   HTTP client header or modifies its value.
3641                 </p>
3642               </dd>
3643               <dt>
3644                 Type:
3645               </dt>
3646               <dd>
3647                 <p>
3648                   Parameterized.
3649                 </p>
3650               </dd>
3651               <dt>
3652                 Parameter:
3653               </dt>
3654               <dd>
3655                 <p>
3656                   Keyword: <span class="QUOTE">"block"</span>, or a user
3657                   defined value that specifies a range of hours.
3658                 </p>
3659               </dd>
3660               <dt>
3661                 Notes:
3662               </dt>
3663               <dd>
3664                 <p>
3665                   Removing this header is useful for filter testing, where
3666                   you want to force a real reload instead of getting status
3667                   code <span class="QUOTE">"304"</span>, which would cause
3668                   the browser to use a cached copy of the page.
3669                 </p>
3670                 <p>
3671                   Instead of removing the header, <tt class=
3672                   "LITERAL">hide-if-modified-since</tt> can also add or
3673                   subtract a random amount of time to/from the header's
3674                   value. You specify a range of minutes where the random
3675                   factor should be chosen from and <span class=
3676                   "APPLICATION">Privoxy</span> does the rest. A negative
3677                   value means subtracting, a positive value adding.
3678                 </p>
3679                 <p>
3680                   Randomizing the value of the <span class=
3681                   "QUOTE">"If-Modified-Since:"</span> makes it less likely
3682                   that the server can use the time as a cookie replacement,
3683                   but you will run into caching problems if the random range
3684                   is too high.
3685                 </p>
3686                 <p>
3687                   It is a good idea to only use a small negative value and
3688                   let <tt class="LITERAL"><a href=
3689                   "actions-file.html#OVERWRITE-LAST-MODIFIED">overwrite-last-modified</a></tt>
3690                   handle the greater changes.
3691                 </p>
3692                 <p>
3693                   It is also recommended to use this action together with <tt
3694                   class="LITERAL"><a href=
3695                   "actions-file.html#CRUNCH-IF-NONE-MATCH">crunch-if-none-match</a></tt>,
3696                   otherwise it's more or less pointless.
3697                 </p>
3698               </dd>
3699               <dt>
3700                 Example usage (section):
3701               </dt>
3702               <dd>
3703                 <p>
3704                 </p>
3705                 <table border="0" bgcolor="#E0E0E0" width="90%">
3706                   <tr>
3707                     <td>
3708 <pre class="SCREEN">
3709 # Let the browser revalidate but make tracking based on the time less likely.
3710 {+hide-if-modified-since{-60} \
3711  +overwrite-last-modified{randomize} \
3712  +crunch-if-none-match}
3713 /
3714 </pre>
3715                     </td>
3716                   </tr>
3717                 </table>
3718               </dd>
3719             </dl>
3720           </div>
3721         </div>
3722         <div class="SECT3">
3723           <h4 class="SECT3">
3724             <a name="HIDE-FROM-HEADER">8.5.23. hide-from-header</a>
3725           </h4>
3726           <div class="VARIABLELIST">
3727             <dl>
3728               <dt>
3729                 Typical use:
3730               </dt>
3731               <dd>
3732                 <p>
3733                   Keep your (old and ill) browser from telling web servers
3734                   your email address
3735                 </p>
3736               </dd>
3737               <dt>
3738                 Effect:
3739               </dt>
3740               <dd>
3741                 <p>
3742                   Deletes any existing <span class="QUOTE">"From:"</span>
3743                   HTTP header, or replaces it with the specified string.
3744                 </p>
3745               </dd>
3746               <dt>
3747                 Type:
3748               </dt>
3749               <dd>
3750                 <p>
3751                   Parameterized.
3752                 </p>
3753               </dd>
3754               <dt>
3755                 Parameter:
3756               </dt>
3757               <dd>
3758                 <p>
3759                   Keyword: <span class="QUOTE">"block"</span>, or any user
3760                   defined value.
3761                 </p>
3762               </dd>
3763               <dt>
3764                 Notes:
3765               </dt>
3766               <dd>
3767                 <p>
3768                   The keyword <span class="QUOTE">"block"</span> will
3769                   completely remove the header (not to be confused with the
3770                   <tt class="LITERAL"><a href=
3771                   "actions-file.html#BLOCK">block</a></tt> action).
3772                 </p>
3773                 <p>
3774                   Alternately, you can specify any value you prefer to be
3775                   sent to the web server. If you do, it is a matter of
3776                   fairness not to use any address that is actually used by a
3777                   real person.
3778                 </p>
3779                 <p>
3780                   This action is rarely needed, as modern web browsers don't
3781                   send <span class="QUOTE">"From:"</span> headers anymore.
3782                 </p>
3783               </dd>
3784               <dt>
3785                 Example usage:
3786               </dt>
3787               <dd>
3788                 <p>
3789                 </p>
3790                 <table border="0" bgcolor="#E0E0E0" width="90%">
3791                   <tr>
3792                     <td>
3793 <pre class="SCREEN">
3794 +hide-from-header{block}
3795 </pre>
3796                     </td>
3797                   </tr>
3798                 </table>
3799                 or
3800                 <table border="0" bgcolor="#E0E0E0" width="90%">
3801                   <tr>
3802                     <td>
3803 <pre class="SCREEN">
3804 +hide-from-header{spam-me-senseless@sittingduck.example.com}
3805 </pre>
3806                     </td>
3807                   </tr>
3808                 </table>
3809               </dd>
3810             </dl>
3811           </div>
3812         </div>
3813         <div class="SECT3">
3814           <h4 class="SECT3">
3815             <a name="HIDE-REFERRER">8.5.24. hide-referrer</a>
3816           </h4>
3817           <a name="HIDE-REFERER"></a>
3818           <div class="VARIABLELIST">
3819             <dl>
3820               <dt>
3821                 Typical use:
3822               </dt>
3823               <dd>
3824                 <p>
3825                   Conceal which link you followed to get to a particular site
3826                 </p>
3827               </dd>
3828               <dt>
3829                 Effect:
3830               </dt>
3831               <dd>
3832                 <p>
3833                   Deletes the <span class="QUOTE">"Referer:"</span> (sic)
3834                   HTTP header from the client request, or replaces it with a
3835                   forged one.
3836                 </p>
3837               </dd>
3838               <dt>
3839                 Type:
3840               </dt>
3841               <dd>
3842                 <p>
3843                   Parameterized.
3844                 </p>
3845               </dd>
3846               <dt>
3847                 Parameter:
3848               </dt>
3849               <dd>
3850                 <ul>
3851                   <li>
3852                     <p>
3853                       <span class="QUOTE">"conditional-block"</span> to
3854                       delete the header completely if the host has changed.
3855                     </p>
3856                   </li>
3857                   <li>
3858                     <p>
3859                       <span class="QUOTE">"conditional-forge"</span> to forge
3860                       the header if the host has changed.
3861                     </p>
3862                   </li>
3863                   <li>
3864                     <p>
3865                       <span class="QUOTE">"block"</span> to delete the header
3866                       unconditionally.
3867                     </p>
3868                   </li>
3869                   <li>
3870                     <p>
3871                       <span class="QUOTE">"forge"</span> to pretend to be
3872                       coming from the homepage of the server we are talking
3873                       to.
3874                     </p>
3875                   </li>
3876                   <li>
3877                     <p>
3878                       Any other string to set a user defined referrer.
3879                     </p>
3880                   </li>
3881                 </ul>
3882               </dd>
3883               <dt>
3884                 Notes:
3885               </dt>
3886               <dd>
3887                 <p>
3888                   <tt class="LITERAL">conditional-block</tt> is the only
3889                   parameter, that isn't easily detected in the server's log
3890                   file. If it blocks the referrer, the request will look like
3891                   the visitor used a bookmark or typed in the address
3892                   directly.
3893                 </p>
3894                 <p>
3895                   Leaving the referrer unmodified for requests on the same
3896                   host allows the server owner to see the visitor's <span
3897                   class="QUOTE">"click path"</span>, but in most cases she
3898                   could also get that information by comparing other parts of
3899                   the log file: for example the User-Agent if it isn't a very
3900                   common one, or the user's IP address if it doesn't change
3901                   between different requests.
3902                 </p>
3903                 <p>
3904                   Always blocking the referrer, or using a custom one, can
3905                   lead to failures on servers that check the referrer before
3906                   they answer any requests, in an attempt to prevent their
3907                   content from being embedded or linked to elsewhere.
3908                 </p>
3909                 <p>
3910                   Both <tt class="LITERAL">conditional-block</tt> and <tt
3911                   class="LITERAL">forge</tt> will work with referrer checks,
3912                   as long as content and valid referring page are on the same
3913                   host. Most of the time that's the case.
3914                 </p>
3915                 <p>
3916                   <tt class="LITERAL">hide-referer</tt> is an alternate
3917                   spelling of <tt class="LITERAL">hide-referrer</tt> and the
3918                   two can be can be freely substituted with each other.
3919                   (<span class="QUOTE">"referrer"</span> is the correct
3920                   English spelling, however the HTTP specification has a bug
3921                   - it requires it to be spelled as <span class=
3922                   "QUOTE">"referer"</span>.)
3923                 </p>
3924               </dd>
3925               <dt>
3926                 Example usage:
3927               </dt>
3928               <dd>
3929                 <p>
3930                 </p>
3931                 <table border="0" bgcolor="#E0E0E0" width="90%">
3932                   <tr>
3933                     <td>
3934 <pre class="SCREEN">
3935 +hide-referrer{forge}
3936 </pre>
3937                     </td>
3938                   </tr>
3939                 </table>
3940                 or
3941                 <table border="0" bgcolor="#E0E0E0" width="90%">
3942                   <tr>
3943                     <td>
3944 <pre class="SCREEN">
3945 +hide-referrer{http://www.yahoo.com/}
3946 </pre>
3947                     </td>
3948                   </tr>
3949                 </table>
3950               </dd>
3951             </dl>
3952           </div>
3953         </div>
3954         <div class="SECT3">
3955           <h4 class="SECT3">
3956             <a name="HIDE-USER-AGENT">8.5.25. hide-user-agent</a>
3957           </h4>
3958           <div class="VARIABLELIST">
3959             <dl>
3960               <dt>
3961                 Typical use:
3962               </dt>
3963               <dd>
3964                 <p>
3965                   Try to conceal your type of browser and client operating
3966                   system
3967                 </p>
3968               </dd>
3969               <dt>
3970                 Effect:
3971               </dt>
3972               <dd>
3973                 <p>
3974                   Replaces the value of the <span class=
3975                   "QUOTE">"User-Agent:"</span> HTTP header in client requests
3976                   with the specified value.
3977                 </p>
3978               </dd>
3979               <dt>
3980                 Type:
3981               </dt>
3982               <dd>
3983                 <p>
3984                   Parameterized.
3985                 </p>
3986               </dd>
3987               <dt>
3988                 Parameter:
3989               </dt>
3990               <dd>
3991                 <p>
3992                   Any user-defined string.
3993                 </p>
3994               </dd>
3995               <dt>
3996                 Notes:
3997               </dt>
3998               <dd>
3999                 <div class="WARNING">
4000                   <table class="WARNING" border="1" width="90%">
4001                     <tr>
4002                       <td align="CENTER">
4003                         <b>Warning</b>
4004                       </td>
4005                     </tr>
4006                     <tr>
4007                       <td align="LEFT">
4008                         <p>
4009                           This can lead to problems on web sites that depend
4010                           on looking at this header in order to customize
4011                           their content for different browsers (which, by the
4012                           way, is <span class="emphasis"><i class=
4013                           "EMPHASIS">NOT</i></span> the right thing to do:
4014                           good web sites work browser-independently).
4015                         </p>
4016                       </td>
4017                     </tr>
4018                   </table>
4019                 </div>
4020                 <p>
4021                   Using this action in multi-user setups or wherever
4022                   different types of browsers will access the same <span
4023                   class="APPLICATION">Privoxy</span> is <span class=
4024                   "emphasis"><i class="EMPHASIS">not recommended</i></span>.
4025                   In single-user, single-browser setups, you might use it to
4026                   delete your OS version information from the headers,
4027                   because it is an invitation to exploit known bugs for your
4028                   OS. It is also occasionally useful to forge this in order
4029                   to access sites that won't let you in otherwise (though
4030                   there may be a good reason in some cases).
4031                 </p>
4032                 <p>
4033                   More information on known user-agent strings can be found
4034                   at <a href="http://www.user-agents.org/" target=
4035                   "_top">http://www.user-agents.org/</a> and <a href=
4036                   "http://en.wikipedia.org/wiki/User_agent" target=
4037                   "_top">http://en.wikipedia.org/wiki/User_agent</a>.
4038                 </p>
4039               </dd>
4040               <dt>
4041                 Example usage:
4042               </dt>
4043               <dd>
4044                 <p>
4045                 </p>
4046                 <table border="0" bgcolor="#E0E0E0" width="90%">
4047                   <tr>
4048                     <td>
4049 <pre class="SCREEN">
4050 +hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)}
4051 </pre>
4052                     </td>
4053                   </tr>
4054                 </table>
4055               </dd>
4056             </dl>
4057           </div>
4058         </div>
4059         <div class="SECT3">
4060           <h4 class="SECT3">
4061             <a name="LIMIT-CONNECT">8.5.26. limit-connect</a>
4062           </h4>
4063           <div class="VARIABLELIST">
4064             <dl>
4065               <dt>
4066                 Typical use:
4067               </dt>
4068               <dd>
4069                 <p>
4070                   Prevent abuse of <span class="APPLICATION">Privoxy</span>
4071                   as a TCP proxy relay or disable SSL for untrusted sites
4072                 </p>
4073               </dd>
4074               <dt>
4075                 Effect:
4076               </dt>
4077               <dd>
4078                 <p>
4079                   Specifies to which ports HTTP CONNECT requests are
4080                   allowable.
4081                 </p>
4082               </dd>
4083               <dt>
4084                 Type:
4085               </dt>
4086               <dd>
4087                 <p>
4088                   Parameterized.
4089                 </p>
4090               </dd>
4091               <dt>
4092                 Parameter:
4093               </dt>
4094               <dd>
4095                 <p>
4096                   A comma-separated list of ports or port ranges (the latter
4097                   using dashes, with the minimum defaulting to 0 and the
4098                   maximum to 65K).
4099                 </p>
4100               </dd>
4101               <dt>
4102                 Notes:
4103               </dt>
4104               <dd>
4105                 <p>
4106                   By default, i.e. if no <tt class=
4107                   "LITERAL">limit-connect</tt> action applies, <span class=
4108                   "APPLICATION">Privoxy</span> allows HTTP CONNECT requests
4109                   to all ports. Use <tt class="LITERAL">limit-connect</tt> if
4110                   fine-grained control is desired for some or all
4111                   destinations.
4112                 </p>
4113                 <p>
4114                   The CONNECT methods exists in HTTP to allow access to
4115                   secure websites (<span class="QUOTE">"https://"</span>
4116                   URLs) through proxies. It works very simply: the proxy
4117                   connects to the server on the specified port, and then
4118                   short-circuits its connections to the client and to the
4119                   remote server. This means CONNECT-enabled proxies can be
4120                   used as TCP relays very easily.
4121                 </p>
4122                 <p>
4123                   <span class="APPLICATION">Privoxy</span> relays HTTPS
4124                   traffic without seeing the decoded content. Websites can
4125                   leverage this limitation to circumvent <span class=
4126                   "APPLICATION">Privoxy</span>'s filters. By specifying an
4127                   invalid port range you can disable HTTPS entirely.
4128                 </p>
4129               </dd>
4130               <dt>
4131                 Example usages:
4132               </dt>
4133               <dd>
4134                 <p>
4135                 </p>
4136                 <table border="0" bgcolor="#E0E0E0" width="90%">
4137                   <tr>
4138                     <td>
4139 <pre class="SCREEN">
4140 +limit-connect{443}                   # Port 443 is OK.
4141 +limit-connect{80,443}                # Ports 80 and 443 are OK.
4142 +limit-connect{-3, 7, 20-100, 500-}   # Ports less than 3, 7, 20 to 100 and above 500 are OK.
4143 +limit-connect{-}                     # All ports are OK
4144 +limit-connect{,}                     # No HTTPS/SSL traffic is allowed
4145 </pre>
4146                     </td>
4147                   </tr>
4148                 </table>
4149               </dd>
4150             </dl>
4151           </div>
4152         </div>
4153         <div class="SECT3">
4154           <h4 class="SECT3">
4155             <a name="PREVENT-COMPRESSION">8.5.27. prevent-compression</a>
4156           </h4>
4157           <div class="VARIABLELIST">
4158             <dl>
4159               <dt>
4160                 Typical use:
4161               </dt>
4162               <dd>
4163                 <p>
4164                   Ensure that servers send the content uncompressed, so it
4165                   can be passed through <tt class="LITERAL"><a href=
4166                   "actions-file.html#FILTER">filter</a></tt>s.
4167                 </p>
4168               </dd>
4169               <dt>
4170                 Effect:
4171               </dt>
4172               <dd>
4173                 <p>
4174                   Removes the Accept-Encoding header which can be used to ask
4175                   for compressed transfer.
4176                 </p>
4177               </dd>
4178               <dt>
4179                 Type:
4180               </dt>
4181               <dd>
4182                 <p>
4183                   Boolean.
4184                 </p>
4185               </dd>
4186               <dt>
4187                 Parameter:
4188               </dt>
4189               <dd>
4190                 <p>
4191                   N/A
4192                 </p>
4193               </dd>
4194               <dt>
4195                 Notes:
4196               </dt>
4197               <dd>
4198                 <p>
4199                   More and more websites send their content compressed by
4200                   default, which is generally a good idea and saves
4201                   bandwidth. But the <tt class="LITERAL"><a href=
4202                   "actions-file.html#FILTER">filter</a></tt> and <tt class=
4203                   "LITERAL"><a href=
4204                   "actions-file.html#DEANIMATE-GIFS">deanimate-gifs</a></tt>
4205                   actions need access to the uncompressed data.
4206                 </p>
4207                 <p>
4208                   When compiled with zlib support (available since <span
4209                   class="APPLICATION">Privoxy</span> 3.0.7), content that
4210                   should be filtered is decompressed on-the-fly and you don't
4211                   have to worry about this action. If you are using an older
4212                   <span class="APPLICATION">Privoxy</span> version, or one
4213                   that hasn't been compiled with zlib support, this action
4214                   can be used to convince the server to send the content
4215                   uncompressed.
4216                 </p>
4217                 <p>
4218                   Most text-based instances compress very well, the size is
4219                   seldom decreased by less than 50%, for markup-heavy
4220                   instances like news feeds saving more than 90% of the
4221                   original size isn't unusual.
4222                 </p>
4223                 <p>
4224                   Not using compression will therefore slow down the
4225                   transfer, and you should only enable this action if you
4226                   really need it. As of <span class=
4227                   "APPLICATION">Privoxy</span> 3.0.7 it's disabled in all
4228                   predefined action settings.
4229                 </p>
4230                 <p>
4231                   Note that some (rare) ill-configured sites don't handle
4232                   requests for uncompressed documents correctly. Broken PHP
4233                   applications tend to send an empty document body, some IIS
4234                   versions only send the beginning of the content. If you
4235                   enable <tt class="LITERAL">prevent-compression</tt> per
4236                   default, you might want to add exceptions for those sites.
4237                   See the example for how to do that.
4238                 </p>
4239               </dd>
4240               <dt>
4241                 Example usage (sections):
4242               </dt>
4243               <dd>
4244                 <p>
4245                 </p>
4246                 <table border="0" bgcolor="#E0E0E0" width="90%">
4247                   <tr>
4248                     <td>
4249 <pre class="SCREEN">
4250 # Selectively turn off compression, and enable a filter
4251 #
4252 { +filter{tiny-textforms} +prevent-compression }
4253 # Match only these sites
4254  .google.
4255  sourceforge.net
4256  sf.net
4257
4258 # Or instead, we could set a universal default:
4259 #
4260 { +prevent-compression }
4261  / # Match all sites
4262
4263 # Then maybe make exceptions for broken sites:
4264 #
4265 { -prevent-compression }
4266 .compusa.com/
4267 </pre>
4268                     </td>
4269                   </tr>
4270                 </table>
4271               </dd>
4272             </dl>
4273           </div>
4274         </div>
4275         <div class="SECT3">
4276           <h4 class="SECT3">
4277             <a name="OVERWRITE-LAST-MODIFIED">8.5.28.
4278             overwrite-last-modified</a>
4279           </h4>
4280           <div class="VARIABLELIST">
4281             <dl>
4282               <dt>
4283                 Typical use:
4284               </dt>
4285               <dd>
4286                 <p>
4287                   Prevent yet another way to track the user's steps between
4288                   sessions.
4289                 </p>
4290               </dd>
4291               <dt>
4292                 Effect:
4293               </dt>
4294               <dd>
4295                 <p>
4296                   Deletes the <span class="QUOTE">"Last-Modified:"</span>
4297                   HTTP server header or modifies its value.
4298                 </p>
4299               </dd>
4300               <dt>
4301                 Type:
4302               </dt>
4303               <dd>
4304                 <p>
4305                   Parameterized.
4306                 </p>
4307               </dd>
4308               <dt>
4309                 Parameter:
4310               </dt>
4311               <dd>
4312                 <p>
4313                   One of the keywords: <span class="QUOTE">"block"</span>,
4314                   <span class="QUOTE">"reset-to-request-time"</span> and
4315                   <span class="QUOTE">"randomize"</span>
4316                 </p>
4317               </dd>
4318               <dt>
4319                 Notes:
4320               </dt>
4321               <dd>
4322                 <p>
4323                   Removing the <span class="QUOTE">"Last-Modified:"</span>
4324                   header is useful for filter testing, where you want to
4325                   force a real reload instead of getting status code <span
4326                   class="QUOTE">"304"</span>, which would cause the browser
4327                   to reuse the old version of the page.
4328                 </p>
4329                 <p>
4330                   The <span class="QUOTE">"randomize"</span> option
4331                   overwrites the value of the <span class=
4332                   "QUOTE">"Last-Modified:"</span> header with a randomly
4333                   chosen time between the original value and the current
4334                   time. In theory the server could send each document with a
4335                   different <span class="QUOTE">"Last-Modified:"</span>
4336                   header to track visits without using cookies. <span class=
4337                   "QUOTE">"Randomize"</span> makes it impossible and the
4338                   browser can still revalidate cached documents.
4339                 </p>
4340                 <p>
4341                   <span class="QUOTE">"reset-to-request-time"</span>
4342                   overwrites the value of the <span class=
4343                   "QUOTE">"Last-Modified:"</span> header with the current
4344                   time. You could use this option together with <tt class=
4345                   "LITERAL"><a href=
4346                   "actions-file.html#HIDE-IF-MODIFIED-SINCE">hide-if-modified-since</a></tt>
4347                   to further customize your random range.
4348                 </p>
4349                 <p>
4350                   The preferred parameter here is <span class=
4351                   "QUOTE">"randomize"</span>. It is safe to use, as long as
4352                   the time settings are more or less correct. If the server
4353                   sets the <span class="QUOTE">"Last-Modified:"</span> header
4354                   to the time of the request, the random range becomes zero
4355                   and the value stays the same. Therefore you should later
4356                   randomize it a second time with <tt class="LITERAL"><a
4357                   href=
4358                   "actions-file.html#HIDE-IF-MODIFIED-SINCE">hided-if-modified-since</a></tt>,
4359                   just to be sure.
4360                 </p>
4361                 <p>
4362                   It is also recommended to use this action together with <tt
4363                   class="LITERAL"><a href=
4364                   "actions-file.html#CRUNCH-IF-NONE-MATCH">crunch-if-none-match</a></tt>.
4365                 </p>
4366               </dd>
4367               <dt>
4368                 Example usage:
4369               </dt>
4370               <dd>
4371                 <p>
4372                 </p>
4373                 <table border="0" bgcolor="#E0E0E0" width="90%">
4374                   <tr>
4375                     <td>
4376 <pre class="SCREEN">
4377 # Let the browser revalidate without being tracked across sessions
4378 { +hide-if-modified-since{-60} \
4379  +overwrite-last-modified{randomize} \
4380  +crunch-if-none-match}
4381 /
4382 </pre>
4383                     </td>
4384                   </tr>
4385                 </table>
4386               </dd>
4387             </dl>
4388           </div>
4389         </div>
4390         <div class="SECT3">
4391           <h4 class="SECT3">
4392             <a name="REDIRECT">8.5.29. redirect</a>
4393           </h4>
4394           <div class="VARIABLELIST">
4395             <dl>
4396               <dt>
4397                 Typical use:
4398               </dt>
4399               <dd>
4400                 <p>
4401                   Redirect requests to other sites.
4402                 </p>
4403               </dd>
4404               <dt>
4405                 Effect:
4406               </dt>
4407               <dd>
4408                 <p>
4409                   Convinces the browser that the requested document has been
4410                   moved to another location and the browser should get it
4411                   from there.
4412                 </p>
4413               </dd>
4414               <dt>
4415                 Type:
4416               </dt>
4417               <dd>
4418                 <p>
4419                   Parameterized
4420                 </p>
4421               </dd>
4422               <dt>
4423                 Parameter:
4424               </dt>
4425               <dd>
4426                 <p>
4427                   An absolute URL or a single pcrs command.
4428                 </p>
4429               </dd>
4430               <dt>
4431                 Notes:
4432               </dt>
4433               <dd>
4434                 <p>
4435                   Requests to which this action applies are answered with a
4436                   HTTP redirect to URLs of your choosing. The new URL is
4437                   either provided as parameter, or derived by applying a
4438                   single pcrs command to the original URL.
4439                 </p>
4440                 <p>
4441                   This action will be ignored if you use it together with <tt
4442                   class="LITERAL"><a href=
4443                   "actions-file.html#BLOCK">block</a></tt>. It can be
4444                   combined with <tt class="LITERAL"><a href=
4445                   "actions-file.html#FAST-REDIRECTS">fast-redirects{check-decoded-url}</a></tt>
4446                   to redirect to a decoded version of a rewritten URL.
4447                 </p>
4448                 <p>
4449                   Use this action carefully, make sure not to create
4450                   redirection loops and be aware that using your own
4451                   redirects might make it possible to fingerprint your
4452                   requests.
4453                 </p>
4454                 <p>
4455                   In case of problems with your redirects, or simply to watch
4456                   them working, enable <a href="config.html#DEBUG">debug
4457                   128</a>.
4458                 </p>
4459               </dd>
4460               <dt>
4461                 Example usages:
4462               </dt>
4463               <dd>
4464                 <p>
4465                 </p>
4466                 <table border="0" bgcolor="#E0E0E0" width="90%">
4467                   <tr>
4468                     <td>
4469 <pre class="SCREEN">
4470 # Replace example.com's style sheet with another one
4471 { +redirect{http://localhost/css-replacements/example.com.css} }
4472  example.com/stylesheet\.css
4473
4474 # Create a short, easy to remember nickname for a favorite site
4475 # (relies on the browser accept and forward invalid URLs to <span class=
4476 "APPLICATION">Privoxy</span>)
4477 { +redirect{http://www.privoxy.org/user-manual/actions-file.html} }
4478  a
4479
4480 # Always use the expanded view for Undeadly.org articles
4481 # (Note the $ at the end of the URL pattern to make sure
4482 # the request for the rewritten URL isn't redirected as well)
4483 {+redirect{s@$@&amp;mode=expanded@}}
4484 undeadly.org/cgi\?action=article&amp;sid=\d*$
4485
4486 # Redirect Google search requests to MSN
4487 {+redirect{s@^http://[^/]*/search\?q=([^&amp;]*).*@http://search.msn.com/results.aspx?q=$1@}}
4488 .google.com/search
4489
4490 # Redirect MSN search requests to Yahoo
4491 {+redirect{s@^http://[^/]*/results\.aspx\?q=([^&amp;]*).*@http://search.yahoo.com/search?p=$1@}}
4492 search.msn.com//results\.aspx\?q=
4493
4494 # Redirect remote requests for this manual
4495 # to the local version delivered by Privoxy
4496 {+redirect{s@^http://www@http://config@}}
4497 www.privoxy.org/user-manual/
4498 </pre>
4499                     </td>
4500                   </tr>
4501                 </table>
4502               </dd>
4503             </dl>
4504           </div>
4505         </div>
4506         <div class="SECT3">
4507           <h4 class="SECT3">
4508             <a name="SERVER-HEADER-FILTER">8.5.30. server-header-filter</a>
4509           </h4>
4510           <div class="VARIABLELIST">
4511             <dl>
4512               <dt>
4513                 Typical use:
4514               </dt>
4515               <dd>
4516                 <p>
4517                   Rewrite or remove single server headers.
4518                 </p>
4519               </dd>
4520               <dt>
4521                 Effect:
4522               </dt>
4523               <dd>
4524                 <p>
4525                   All server headers to which this action applies are
4526                   filtered on-the-fly through the specified regular
4527                   expression based substitutions.
4528                 </p>
4529               </dd>
4530               <dt>
4531                 Type:
4532               </dt>
4533               <dd>
4534                 <p>
4535                   Parameterized.
4536                 </p>
4537               </dd>
4538               <dt>
4539                 Parameter:
4540               </dt>
4541               <dd>
4542                 <p>
4543                   The name of a server-header filter, as defined in one of
4544                   the <a href="filter-file.html">filter files</a>.
4545                 </p>
4546               </dd>
4547               <dt>
4548                 Notes:
4549               </dt>
4550               <dd>
4551                 <p>
4552                   Server-header filters are applied to each header on its
4553                   own, not to all at once. This makes it easier to diagnose
4554                   problems, but on the downside you can't write filters that
4555                   only change header x if header y's value is z. You can do
4556                   that by using tags though.
4557                 </p>
4558                 <p>
4559                   Server-header filters are executed after the other header
4560                   actions have finished and use their output as input.
4561                 </p>
4562                 <p>
4563                   Please refer to the <a href="filter-file.html">filter file
4564                   chapter</a> to learn which server-header filters are
4565                   available by default, and how to create your own.
4566                 </p>
4567               </dd>
4568               <dt>
4569                 Example usage (section):
4570               </dt>
4571               <dd>
4572                 <p>
4573                 </p>
4574                 <table border="0" bgcolor="#E0E0E0" width="90%">
4575                   <tr>
4576                     <td>
4577 <pre class="SCREEN">
4578 {+server-header-filter{html-to-xml}}
4579 example.org/xml-instance-that-is-delivered-as-html
4580
4581 {+server-header-filter{xml-to-html}}
4582 example.org/instance-that-is-delivered-as-xml-but-is-not
4583
4584 </pre>
4585                     </td>
4586                   </tr>
4587                 </table>
4588               </dd>
4589             </dl>
4590           </div>
4591         </div>
4592         <div class="SECT3">
4593           <h4 class="SECT3">
4594             <a name="SERVER-HEADER-TAGGER">8.5.31. server-header-tagger</a>
4595           </h4>
4596           <div class="VARIABLELIST">
4597             <dl>
4598               <dt>
4599                 Typical use:
4600               </dt>
4601               <dd>
4602                 <p>
4603                   Enable or disable filters based on the Content-Type header.
4604                 </p>
4605               </dd>
4606               <dt>
4607                 Effect:
4608               </dt>
4609               <dd>
4610                 <p>
4611                   Server headers to which this action applies are filtered
4612                   on-the-fly through the specified regular expression based
4613                   substitutions, the result is used as tag.
4614                 </p>
4615               </dd>
4616               <dt>
4617                 Type:
4618               </dt>
4619               <dd>
4620                 <p>
4621                   Parameterized.
4622                 </p>
4623               </dd>
4624               <dt>
4625                 Parameter:
4626               </dt>
4627               <dd>
4628                 <p>
4629                   The name of a server-header tagger, as defined in one of
4630                   the <a href="filter-file.html">filter files</a>.
4631                 </p>
4632               </dd>
4633               <dt>
4634                 Notes:
4635               </dt>
4636               <dd>
4637                 <p>
4638                   Server-header taggers are applied to each header on its
4639                   own, and as the header isn't modified, each tagger <span
4640                   class="QUOTE">"sees"</span> the original.
4641                 </p>
4642                 <p>
4643                   Server-header taggers are executed before all other header
4644                   actions that modify server headers. Their tags can be used
4645                   to control all of the other server-header actions, the
4646                   content filters and the crunch actions (<a href=
4647                   "actions-file.html#REDIRECT">redirect</a> and <a href=
4648                   "actions-file.html#BLOCK">block</a>).
4649                 </p>
4650                 <p>
4651                   Obviously crunching based on tags created by server-header
4652                   taggers doesn't prevent the request from showing up in the
4653                   server's log file.
4654                 </p>
4655               </dd>
4656               <dt>
4657                 Example usage (section):
4658               </dt>
4659               <dd>
4660                 <p>
4661                 </p>
4662                 <table border="0" bgcolor="#E0E0E0" width="90%">
4663                   <tr>
4664                     <td>
4665 <pre class="SCREEN">
4666 # Tag every request with the content type declared by the server
4667 {+server-header-tagger{content-type}}
4668 /
4669
4670 </pre>
4671                     </td>
4672                   </tr>
4673                 </table>
4674               </dd>
4675             </dl>
4676           </div>
4677         </div>
4678         <div class="SECT3">
4679           <h4 class="SECT3">
4680             <a name="SESSION-COOKIES-ONLY">8.5.32. session-cookies-only</a>
4681           </h4>
4682           <div class="VARIABLELIST">
4683             <dl>
4684               <dt>
4685                 Typical use:
4686               </dt>
4687               <dd>
4688                 <p>
4689                   Allow only temporary <span class="QUOTE">"session"</span>
4690                   cookies (for the current browser session <span class=
4691                   "emphasis"><i class="EMPHASIS">only</i></span>).
4692                 </p>
4693               </dd>
4694               <dt>
4695                 Effect:
4696               </dt>
4697               <dd>
4698                 <p>
4699                   Deletes the <span class="QUOTE">"expires"</span> field from
4700                   <span class="QUOTE">"Set-Cookie:"</span> server headers.
4701                   Most browsers will not store such cookies permanently and
4702                   forget them in between sessions.
4703                 </p>
4704               </dd>
4705               <dt>
4706                 Type:
4707               </dt>
4708               <dd>
4709                 <p>
4710                   Boolean.
4711                 </p>
4712               </dd>
4713               <dt>
4714                 Parameter:
4715               </dt>
4716               <dd>
4717                 <p>
4718                   N/A
4719                 </p>
4720               </dd>
4721               <dt>
4722                 Notes:
4723               </dt>
4724               <dd>
4725                 <p>
4726                   This is less strict than <tt class="LITERAL"><a href=
4727                   "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a></tt>
4728                   / <tt class="LITERAL"><a href=
4729                   "actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a></tt>
4730                   and allows you to browse websites that insist or rely on
4731                   setting cookies, without compromising your privacy too
4732                   badly.
4733                 </p>
4734                 <p>
4735                   Most browsers will not permanently store cookies that have
4736                   been processed by <tt class=
4737                   "LITERAL">session-cookies-only</tt> and will forget about
4738                   them between sessions. This makes profiling cookies
4739                   useless, but won't break sites which require cookies so
4740                   that you can log in for transactions. This is generally
4741                   turned on for all sites, and is the recommended setting.
4742                 </p>
4743                 <p>
4744                   It makes <span class="emphasis"><i class="EMPHASIS">no
4745                   sense at all</i></span> to use <tt class=
4746                   "LITERAL">session-cookies-only</tt> together with <tt
4747                   class="LITERAL"><a href=
4748                   "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a></tt>
4749                   or <tt class="LITERAL"><a href=
4750                   "actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a></tt>.
4751                   If you do, cookies will be plainly killed.
4752                 </p>
4753                 <p>
4754                   Note that it is up to the browser how it handles such
4755                   cookies without an <span class="QUOTE">"expires"</span>
4756                   field. If you use an exotic browser, you might want to try
4757                   it out to be sure.
4758                 </p>
4759                 <p>
4760                   This setting also has no effect on cookies that may have
4761                   been stored previously by the browser before starting <span
4762                   class="APPLICATION">Privoxy</span>. These would have to be
4763                   removed manually.
4764                 </p>
4765                 <p>
4766                   <span class="APPLICATION">Privoxy</span> also uses the <a
4767                   href=
4768                   "actions-file.html#FILTER-CONTENT-COOKIES">content-cookies
4769                   filter</a> to block some types of cookies. Content cookies
4770                   are not effected by <tt class=
4771                   "LITERAL">session-cookies-only</tt>.
4772                 </p>
4773               </dd>
4774               <dt>
4775                 Example usage:
4776               </dt>
4777               <dd>
4778                 <p>
4779                 </p>
4780                 <table border="0" bgcolor="#E0E0E0" width="90%">
4781                   <tr>
4782                     <td>
4783 <pre class="SCREEN">
4784 +session-cookies-only
4785 </pre>
4786                     </td>
4787                   </tr>
4788                 </table>
4789               </dd>
4790             </dl>
4791           </div>
4792         </div>
4793         <div class="SECT3">
4794           <h4 class="SECT3">
4795             <a name="SET-IMAGE-BLOCKER">8.5.33. set-image-blocker</a>
4796           </h4>
4797           <div class="VARIABLELIST">
4798             <dl>
4799               <dt>
4800                 Typical use:
4801               </dt>
4802               <dd>
4803                 <p>
4804                   Choose the replacement for blocked images
4805                 </p>
4806               </dd>
4807               <dt>
4808                 Effect:
4809               </dt>
4810               <dd>
4811                 <p>
4812                   This action alone doesn't do anything noticeable. If <span
4813                   class="emphasis"><i class="EMPHASIS">both</i></span> <tt
4814                   class="LITERAL"><a href=
4815                   "actions-file.html#BLOCK">block</a></tt> <span class=
4816                   "emphasis"><i class="EMPHASIS">and</i></span> <tt class=
4817                   "LITERAL"><a href=
4818                   "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a></tt>
4819                   <span class="emphasis"><i class="EMPHASIS">also</i></span>
4820                   apply, i.e. if the request is to be blocked as an image,
4821                   <span class="emphasis"><i class="EMPHASIS">then</i></span>
4822                   the parameter of this action decides what will be sent as a
4823                   replacement.
4824                 </p>
4825               </dd>
4826               <dt>
4827                 Type:
4828               </dt>
4829               <dd>
4830                 <p>
4831                   Parameterized.
4832                 </p>
4833               </dd>
4834               <dt>
4835                 Parameter:
4836               </dt>
4837               <dd>
4838                 <ul>
4839                   <li>
4840                     <p>
4841                       <span class="QUOTE">"pattern"</span> to send a built-in
4842                       checkerboard pattern image. The image is visually
4843                       decent, scales very well, and makes it obvious where
4844                       banners were busted.
4845                     </p>
4846                   </li>
4847                   <li>
4848                     <p>
4849                       <span class="QUOTE">"blank"</span> to send a built-in
4850                       transparent image. This makes banners disappear
4851                       completely, but makes it hard to detect where <span
4852                       class="APPLICATION">Privoxy</span> has blocked images
4853                       on a given page and complicates troubleshooting if
4854                       <span class="APPLICATION">Privoxy</span> has blocked
4855                       innocent images, like navigation icons.
4856                     </p>
4857                   </li>
4858                   <li>
4859                     <p>
4860                       <span class="QUOTE">"<tt class=
4861                       "REPLACEABLE"><i>target-url</i></tt>"</span> to send a
4862                       redirect to <tt class=
4863                       "REPLACEABLE"><i>target-url</i></tt>. You can redirect
4864                       to any image anywhere, even in your local filesystem
4865                       via <span class="QUOTE">"file:///"</span> URL. (But
4866                       note that not all browsers support redirecting to a
4867                       local file system).
4868                     </p>
4869                     <p>
4870                       A good application of redirects is to use special <span
4871                       class="APPLICATION">Privoxy</span>-built-in URLs, which
4872                       send the built-in images, as <tt class=
4873                       "REPLACEABLE"><i>target-url</i></tt>. This has the same
4874                       visual effect as specifying <span class=
4875                       "QUOTE">"blank"</span> or <span class=
4876                       "QUOTE">"pattern"</span> in the first place, but
4877                       enables your browser to cache the replacement image,
4878                       instead of requesting it over and over again.
4879                     </p>
4880                   </li>
4881                 </ul>
4882               </dd>
4883               <dt>
4884                 Notes:
4885               </dt>
4886               <dd>
4887                 <p>
4888                   The URLs for the built-in images are <span class=
4889                   "QUOTE">"http://config.privoxy.org/send-banner?type=<tt
4890                   class="REPLACEABLE"><i>type</i></tt>"</span>, where <tt
4891                   class="REPLACEABLE"><i>type</i></tt> is either <span class=
4892                   "QUOTE">"blank"</span> or <span class=
4893                   "QUOTE">"pattern"</span>.
4894                 </p>
4895                 <p>
4896                   There is a third (advanced) type, called <span class=
4897                   "QUOTE">"auto"</span>. It is <span class="emphasis"><i
4898                   class="EMPHASIS">NOT</i></span> to be used in <tt class=
4899                   "LITERAL">set-image-blocker</tt>, but meant for use from <a
4900                   href="filter-file.html">filters</a>. Auto will select the
4901                   type of image that would have applied to the referring
4902                   page, had it been an image.
4903                 </p>
4904               </dd>
4905               <dt>
4906                 Example usage:
4907               </dt>
4908               <dd>
4909                 <p>
4910                   Built-in pattern:
4911                 </p>
4912                 <p>
4913                 </p>
4914                 <table border="0" bgcolor="#E0E0E0" width="90%">
4915                   <tr>
4916                     <td>
4917 <pre class="SCREEN">
4918 +set-image-blocker{pattern}
4919 </pre>
4920                     </td>
4921                   </tr>
4922                 </table>
4923
4924                 <p>
4925                   Redirect to the BSD daemon:
4926                 </p>
4927                 <p>
4928                 </p>
4929                 <table border="0" bgcolor="#E0E0E0" width="90%">
4930                   <tr>
4931                     <td>
4932 <pre class="SCREEN">
4933 +set-image-blocker{http://www.freebsd.org/gifs/dae_up3.gif}
4934 </pre>
4935                     </td>
4936                   </tr>
4937                 </table>
4938
4939                 <p>
4940                   Redirect to the built-in pattern for better caching:
4941                 </p>
4942                 <p>
4943                 </p>
4944                 <table border="0" bgcolor="#E0E0E0" width="90%">
4945                   <tr>
4946                     <td>
4947 <pre class="SCREEN">
4948 +set-image-blocker{http://config.privoxy.org/send-banner?type=pattern}
4949 </pre>
4950                     </td>
4951                   </tr>
4952                 </table>
4953               </dd>
4954             </dl>
4955           </div>
4956         </div>
4957         <div class="SECT3">
4958           <h3 class="SECT3">
4959             <a name="AEN4549">8.5.34. Summary</a>
4960           </h3>
4961           <p>
4962             Note that many of these actions have the potential to cause a
4963             page to misbehave, possibly even not to display at all. There are
4964             many ways a site designer may choose to design his site, and what
4965             HTTP header content, and other criteria, he may depend on. There
4966             is no way to have hard and fast rules for all sites. See the <a
4967             href="appendix.html#ACTIONSANAT">Appendix</a> for a brief example
4968             on troubleshooting actions.
4969           </p>
4970         </div>
4971       </div>
4972       <div class="SECT2">
4973         <h2 class="SECT2">
4974           <a name="ALIASES">8.6. Aliases</a>
4975         </h2>
4976         <p>
4977           Custom <span class="QUOTE">"actions"</span>, known to <span class=
4978           "APPLICATION">Privoxy</span> as <span class=
4979           "QUOTE">"aliases"</span>, can be defined by combining other
4980           actions. These can in turn be invoked just like the built-in
4981           actions. Currently, an alias name can contain any character except
4982           space, tab, <span class="QUOTE">"="</span>, <span class=
4983           "QUOTE">"{"</span> and <span class="QUOTE">"}"</span>, but we <span
4984           class="emphasis"><i class="EMPHASIS">strongly recommend</i></span>
4985           that you only use <span class="QUOTE">"a"</span> to <span class=
4986           "QUOTE">"z"</span>, <span class="QUOTE">"0"</span> to <span class=
4987           "QUOTE">"9"</span>, <span class="QUOTE">"+"</span>, and <span
4988           class="QUOTE">"-"</span>. Alias names are not case sensitive, and
4989           are not required to start with a <span class="QUOTE">"+"</span> or
4990           <span class="QUOTE">"-"</span> sign, since they are merely
4991           textually expanded.
4992         </p>
4993         <p>
4994           Aliases can be used throughout the actions file, but they <span
4995           class="emphasis"><i class="EMPHASIS">must be defined in a special
4996           section at the top of the file!</i></span> And there can only be
4997           one such section per actions file. Each actions file may have its
4998           own alias section, and the aliases defined in it are only visible
4999           within that file.
5000         </p>
5001         <p>
5002           There are two main reasons to use aliases: One is to save typing
5003           for frequently used combinations of actions, the other one is a
5004           gain in flexibility: If you decide once how you want to handle
5005           shops by defining an alias called <span class=
5006           "QUOTE">"shop"</span>, you can later change your policy on shops in
5007           <span class="emphasis"><i class="EMPHASIS">one</i></span> place,
5008           and your changes will take effect everywhere in the actions file
5009           where the <span class="QUOTE">"shop"</span> alias is used. Calling
5010           aliases by their purpose also makes your actions files more
5011           readable.
5012         </p>
5013         <p>
5014           Currently, there is one big drawback to using aliases, though:
5015           <span class="APPLICATION">Privoxy</span>'s built-in web-based
5016           action file editor honors aliases when reading the actions files,
5017           but it expands them before writing. So the effects of your aliases
5018           are of course preserved, but the aliases themselves are lost when
5019           you edit sections that use aliases with it.
5020         </p>
5021         <p>
5022           Now let's define some aliases...
5023         </p>
5024         <p>
5025         </p>
5026         <table border="0" bgcolor="#E0E0E0" width="100%">
5027           <tr>
5028             <td>
5029 <pre class="SCREEN">
5030  # Useful custom aliases we can use later.
5031  #
5032  # Note the (required!) section header line and that this section
5033  # must be at the top of the actions file!
5034  #
5035  {{alias}}
5036
5037  # These aliases just save typing later:
5038  # (Note that some already use other aliases!)
5039  #
5040  +crunch-all-cookies = +<a href=
5041 "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a> +<a
5042 href="actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a>
5043  -crunch-all-cookies = -<a href=
5044 "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a> -<a
5045 href="actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a>
5046  +block-as-image      = +block{Blocked image.} +handle-as-image
5047  allow-all-cookies   = -crunch-all-cookies -<a href=
5048 "actions-file.html#SESSION-COOKIES-ONLY">session-cookies-only</a> -<a href=
5049 "actions-file.html#FILTER-CONTENT-COOKIES">filter{content-cookies}</a>
5050
5051  # These aliases define combinations of actions
5052  # that are useful for certain types of sites:
5053  #
5054  fragile     = -<a href="actions-file.html#BLOCK">block</a> -<a href=
5055 "actions-file.html#FILTER">filter</a> -crunch-all-cookies -<a href=
5056 "actions-file.html#FAST-REDIRECTS">fast-redirects</a> -<a href=
5057 "actions-file.html#HIDE-REFERER">hide-referrer</a> -<a href=
5058 "actions-file.html#PREVENT-COMPRESSION">prevent-compression</a>
5059
5060  shop        = -crunch-all-cookies -<a href=
5061 "actions-file.html#FILTER-ALL-POPUPS">filter{all-popups}</a>
5062
5063  # Short names for other aliases, for really lazy people ;-)
5064  #
5065  c0 = +crunch-all-cookies
5066  c1 = -crunch-all-cookies
5067 </pre>
5068             </td>
5069           </tr>
5070         </table>
5071
5072         <p>
5073           ...and put them to use. These sections would appear in the lower
5074           part of an actions file and define exceptions to the default
5075           actions (as specified further up for the <span class=
5076           "QUOTE">"/"</span> pattern):
5077         </p>
5078         <p>
5079         </p>
5080         <table border="0" bgcolor="#E0E0E0" width="100%">
5081           <tr>
5082             <td>
5083 <pre class="SCREEN">
5084  # These sites are either very complex or very keen on
5085  # user data and require minimal interference to work:
5086  #
5087  {fragile}
5088  .office.microsoft.com
5089  .windowsupdate.microsoft.com
5090  # Gmail is really mail.google.com, not gmail.com
5091  mail.google.com
5092
5093  # Shopping sites:
5094  # Allow cookies (for setting and retrieving your customer data)
5095  #
5096  {shop}
5097  .quietpc.com
5098  .worldpay.com   # for quietpc.com
5099  mybank.example.com
5100
5101  # These shops require pop-ups:
5102  #
5103  {-filter{all-popups} -filter{unsolicited-popups}}
5104   .dabs.com
5105   .overclockers.co.uk
5106 </pre>
5107             </td>
5108           </tr>
5109         </table>
5110
5111         <p>
5112           Aliases like <span class="QUOTE">"shop"</span> and <span class=
5113           "QUOTE">"fragile"</span> are typically used for <span class=
5114           "QUOTE">"problem"</span> sites that require more than one action to
5115           be disabled in order to function properly.
5116         </p>
5117       </div>
5118       <div class="SECT2">
5119         <h2 class="SECT2">
5120           <a name="ACT-EXAMPLES">8.7. Actions Files Tutorial</a>
5121         </h2>
5122         <p>
5123           The above chapters have shown <a href="actions-file.html">which
5124           actions files there are and how they are organized</a>, how actions
5125           are <a href="actions-file.html#ACTIONS">specified</a> and <a href=
5126           "actions-file.html#ACTIONS-APPLY">applied to URLs</a>, how <a href=
5127           "actions-file.html#AF-PATTERNS">patterns</a> work, and how to
5128           define and use <a href="actions-file.html#ALIASES">aliases</a>.
5129           Now, let's look at an example <tt class=
5130           "FILENAME">match-all.action</tt>, <tt class=
5131           "FILENAME">default.action</tt> and <tt class=
5132           "FILENAME">user.action</tt> file and see how all these pieces come
5133           together:
5134         </p>
5135         <div class="SECT3">
5136           <h3 class="SECT3">
5137             <a name="AEN4613">8.7.1. match-all.action</a>
5138           </h3>
5139           <p>
5140             Remember <span class="emphasis"><i class="EMPHASIS">all actions
5141             are disabled when matching starts</i></span>, so we have to
5142             explicitly enable the ones we want.
5143           </p>
5144           <p>
5145             While the <tt class="FILENAME">match-all.action</tt> file only
5146             contains a single section, it is probably the most important one.
5147             It has only one pattern, <span class="QUOTE">"<tt class=
5148             "LITERAL">/</tt>"</span>, but this pattern <a href=
5149             "actions-file.html#AF-PATTERNS">matches all URLs</a>. Therefore,
5150             the set of actions used in this <span class=
5151             "QUOTE">"default"</span> section <span class="emphasis"><i class=
5152             "EMPHASIS">will be applied to all requests as a start</i></span>.
5153             It can be partly or wholly overridden by other actions files like
5154             <tt class="FILENAME">default.action</tt> and <tt class=
5155             "FILENAME">user.action</tt>, but it will still be largely
5156             responsible for your overall browsing experience.
5157           </p>
5158           <p>
5159             Again, at the start of matching, all actions are disabled, so
5160             there is no need to disable any actions here. (Remember: a <span
5161             class="QUOTE">"+"</span> preceding the action name enables the
5162             action, a <span class="QUOTE">"-"</span> disables!). Also note
5163             how this long line has been made more readable by splitting it
5164             into multiple lines with line continuation.
5165           </p>
5166           <p>
5167           </p>
5168           <table border="0" bgcolor="#E0E0E0" width="100%">
5169             <tr>
5170               <td>
5171 <pre class="SCREEN">
5172 { \
5173  +<a href=
5174 "actions-file.html#CHANGE-X-FORWARDED-FOR">change-x-forwarded-for{block}</a> \
5175  +<a href="actions-file.html#HIDE-FROM-HEADER">hide-from-header{block}</a> \
5176  +<a href=
5177 "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker{pattern}</a> \
5178 }
5179 / # Match all URLs
5180 </pre>
5181               </td>
5182             </tr>
5183           </table>
5184
5185           <p>
5186             The default behavior is now set.
5187           </p>
5188         </div>
5189         <div class="SECT3">
5190           <h3 class="SECT3">
5191             <a name="AEN4635">8.7.2. default.action</a>
5192           </h3>
5193           <p>
5194             If you aren't a developer, there's no need for you to edit the
5195             <tt class="FILENAME">default.action</tt> file. It is maintained
5196             by the <span class="APPLICATION">Privoxy</span> developers and if
5197             you disagree with some of the sections, you should overrule them
5198             in your <tt class="FILENAME">user.action</tt>.
5199           </p>
5200           <p>
5201             Understanding the <tt class="FILENAME">default.action</tt> file
5202             can help you with your <tt class="FILENAME">user.action</tt>,
5203             though.
5204           </p>
5205           <p>
5206             The first section in this file is a special section for internal
5207             use that prevents older <span class="APPLICATION">Privoxy</span>
5208             versions from reading the file:
5209           </p>
5210           <p>
5211           </p>
5212           <table border="0" bgcolor="#E0E0E0" width="100%">
5213             <tr>
5214               <td>
5215 <pre class="SCREEN">
5216 ##########################################################################
5217 # Settings -- Don't change! For internal Privoxy use ONLY.
5218 ##########################################################################
5219 {{settings}}
5220 for-privoxy-version=3.0.11
5221 </pre>
5222               </td>
5223             </tr>
5224           </table>
5225
5226           <p>
5227             After that comes the (optional) alias section. We'll use the
5228             example section from the above <a href=
5229             "actions-file.html#ALIASES">chapter on aliases</a>, that also
5230             explains why and how aliases are used:
5231           </p>
5232           <p>
5233           </p>
5234           <table border="0" bgcolor="#E0E0E0" width="100%">
5235             <tr>
5236               <td>
5237 <pre class="SCREEN">
5238 ##########################################################################
5239 # Aliases
5240 ##########################################################################
5241 {{alias}}
5242
5243  # These aliases just save typing later:
5244  # (Note that some already use other aliases!)
5245  #
5246  +crunch-all-cookies = +<a href=
5247 "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a> +<a
5248 href="actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a>
5249  -crunch-all-cookies = -<a href=
5250 "actions-file.html#CRUNCH-INCOMING-COOKIES">crunch-incoming-cookies</a> -<a
5251 href="actions-file.html#CRUNCH-OUTGOING-COOKIES">crunch-outgoing-cookies</a>
5252  +block-as-image      = +block{Blocked image.} +handle-as-image
5253  mercy-for-cookies   = -crunch-all-cookies -<a href=
5254 "actions-file.html#SESSION-COOKIES-ONLY">session-cookies-only</a> -<a href=
5255 "actions-file.html#FILTER-CONTENT-COOKIES">filter{content-cookies}</a>
5256
5257  # These aliases define combinations of actions
5258  # that are useful for certain types of sites:
5259  #
5260  fragile     = -<a href="actions-file.html#BLOCK">block</a> -<a href=
5261 "actions-file.html#FILTER">filter</a> -crunch-all-cookies -<a href=
5262 "actions-file.html#FAST-REDIRECTS">fast-redirects</a> -<a href=
5263 "actions-file.html#HIDE-REFERER">hide-referrer</a>
5264  shop        = -crunch-all-cookies -<a href=
5265 "actions-file.html#FILTER-ALL-POPUPS">filter{all-popups}</a>
5266 </pre>
5267               </td>
5268             </tr>
5269           </table>
5270
5271           <p>
5272             The first of our specialized sections is concerned with <span
5273             class="QUOTE">"fragile"</span> sites, i.e. sites that require
5274             minimum interference, because they are either very complex or
5275             very keen on tracking you (and have mechanisms in place that make
5276             them unusable for people who avoid being tracked). We will simply
5277             use our pre-defined <tt class="LITERAL">fragile</tt> alias
5278             instead of stating the list of actions explicitly:
5279           </p>
5280           <p>
5281           </p>
5282           <table border="0" bgcolor="#E0E0E0" width="100%">
5283             <tr>
5284               <td>
5285 <pre class="SCREEN">
5286 ##########################################################################
5287 # Exceptions for sites that'll break under the default action set:
5288 ##########################################################################
5289
5290 # "Fragile" Use a minimum set of actions for these sites (see alias above):
5291 #
5292 { fragile }
5293 .office.microsoft.com           # surprise, surprise!
5294 .windowsupdate.microsoft.com
5295 mail.google.com
5296 </pre>
5297               </td>
5298             </tr>
5299           </table>
5300
5301           <p>
5302             Shopping sites are not as fragile, but they typically require
5303             cookies to log in, and pop-up windows for shopping carts or item
5304             details. Again, we'll use a pre-defined alias:
5305           </p>
5306           <p>
5307           </p>
5308           <table border="0" bgcolor="#E0E0E0" width="100%">
5309             <tr>
5310               <td>
5311 <pre class="SCREEN">
5312 # Shopping sites:
5313 #
5314 { shop }
5315 .quietpc.com
5316 .worldpay.com   # for quietpc.com
5317 .jungle.com
5318 .scan.co.uk
5319 </pre>
5320               </td>
5321             </tr>
5322           </table>
5323
5324           <p>
5325             The <tt class="LITERAL"><a href=
5326             "actions-file.html#FAST-REDIRECTS">fast-redirects</a></tt>
5327             action, which may have been enabled in <tt class=
5328             "FILENAME">match-all.action</tt>, breaks some sites. So disable
5329             it for popular sites where we know it misbehaves:
5330           </p>
5331           <p>
5332           </p>
5333           <table border="0" bgcolor="#E0E0E0" width="100%">
5334             <tr>
5335               <td>
5336 <pre class="SCREEN">
5337 { -<a href="actions-file.html#FAST-REDIRECTS">fast-redirects</a> }
5338 login.yahoo.com
5339 edit.*.yahoo.com
5340 .google.com
5341 .altavista.com/.*(like|url|link):http
5342 .altavista.com/trans.*urltext=http
5343 .nytimes.com
5344 </pre>
5345               </td>
5346             </tr>
5347           </table>
5348
5349           <p>
5350             It is important that <span class="APPLICATION">Privoxy</span>
5351             knows which URLs belong to images, so that <span class=
5352             "emphasis"><i class="EMPHASIS">if</i></span> they are to be
5353             blocked, a substitute image can be sent, rather than an HTML
5354             page. Contacting the remote site to find out is not an option,
5355             since it would destroy the loading time advantage of banner
5356             blocking, and it would feed the advertisers information about
5357             you. We can mark any URL as an image with the <tt class=
5358             "LITERAL"><a href=
5359             "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a></tt>
5360             action, and marking all URLs that end in a known image file
5361             extension is a good start:
5362           </p>
5363           <p>
5364           </p>
5365           <table border="0" bgcolor="#E0E0E0" width="100%">
5366             <tr>
5367               <td>
5368 <pre class="SCREEN">
5369 ##########################################################################
5370 # Images:
5371 ##########################################################################
5372
5373 # Define which file types will be treated as images, in case they get
5374 # blocked further down this file:
5375 #
5376 { +<a href="actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a> }
5377 /.*\.(gif|jpe?g|png|bmp|ico)$
5378 </pre>
5379               </td>
5380             </tr>
5381           </table>
5382
5383           <p>
5384             And then there are known banner sources. They often use scripts
5385             to generate the banners, so it won't be visible from the URL that
5386             the request is for an image. Hence we block them <span class=
5387             "emphasis"><i class="EMPHASIS">and</i></span> mark them as images
5388             in one go, with the help of our <tt class=
5389             "LITERAL">+block-as-image</tt> alias defined above. (We could of
5390             course just as well use <tt class="LITERAL">+<a href=
5391             "actions-file.html#BLOCK">block</a> +<a href=
5392             "actions-file.html#HANDLE-AS-IMAGE">handle-as-image</a></tt>
5393             here.) Remember that the type of the replacement image is chosen
5394             by the <tt class="LITERAL"><a href=
5395             "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker</a></tt>
5396             action. Since all URLs have matched the default section with its
5397             <tt class="LITERAL">+<a href=
5398             "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker</a>{pattern}</tt>
5399             action before, it still applies and needn't be repeated:
5400           </p>
5401           <p>
5402           </p>
5403           <table border="0" bgcolor="#E0E0E0" width="100%">
5404             <tr>
5405               <td>
5406 <pre class="SCREEN">
5407 # Known ad generators:
5408 #
5409 { +block-as-image }
5410 ar.atwola.com
5411 .ad.doubleclick.net
5412 .ad.*.doubleclick.net
5413 .a.yimg.com/(?:(?!/i/).)*$
5414 .a[0-9].yimg.com/(?:(?!/i/).)*$
5415 bs*.gsanet.com
5416 .qkimg.net
5417 </pre>
5418               </td>
5419             </tr>
5420           </table>
5421
5422           <p>
5423             One of the most important jobs of <span class=
5424             "APPLICATION">Privoxy</span> is to block banners. Many of these
5425             can be <span class="QUOTE">"blocked"</span> by the <tt class=
5426             "LITERAL"><a href=
5427             "actions-file.html#FILTER">filter</a>{banners-by-size}</tt>
5428             action, which we enabled above, and which deletes the references
5429             to banner images from the pages while they are loaded, so the
5430             browser doesn't request them anymore, and hence they don't need
5431             to be blocked here. But this naturally doesn't catch all banners,
5432             and some people choose not to use filters, so we need a
5433             comprehensive list of patterns for banner URLs here, and apply
5434             the <tt class="LITERAL"><a href=
5435             "actions-file.html#BLOCK">block</a></tt> action to them.
5436           </p>
5437           <p>
5438             First comes many generic patterns, which do most of the work, by
5439             matching typical domain and path name components of banners. Then
5440             comes a list of individual patterns for specific sites, which is
5441             omitted here to keep the example short:
5442           </p>
5443           <p>
5444           </p>
5445           <table border="0" bgcolor="#E0E0E0" width="100%">
5446             <tr>
5447               <td>
5448 <pre class="SCREEN">
5449 ##########################################################################
5450 # Block these fine banners:
5451 ##########################################################################
5452 { <a href="actions-file.html#BLOCK">+block{Banner ads.}</a> }
5453
5454 # Generic patterns:
5455 #
5456 ad*.
5457 .*ads.
5458 banner?.
5459 count*.
5460 /.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?)
5461 /(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/
5462
5463 # Site-specific patterns (abbreviated):
5464 #
5465 .hitbox.com
5466 </pre>
5467               </td>
5468             </tr>
5469           </table>
5470
5471           <p>
5472             It's quite remarkable how many advertisers actually call their
5473             banner servers ads.<tt class=
5474             "REPLACEABLE"><i>company</i></tt>.com, or call the directory in
5475             which the banners are stored simply <span class=
5476             "QUOTE">"banners"</span>. So the above generic patterns are
5477             surprisingly effective.
5478           </p>
5479           <p>
5480             But being very generic, they necessarily also catch URLs that we
5481             don't want to block. The pattern <tt class="LITERAL">.*ads.</tt>
5482             e.g. catches <span class="QUOTE">"nasty-<span class="emphasis"><i
5483             class="EMPHASIS">ads</i></span>.nasty-corp.com"</span> as
5484             intended, but also <span class="QUOTE">"downlo<span class=
5485             "emphasis"><i class=
5486             "EMPHASIS">ads</i></span>.sourcefroge.net"</span> or <span class=
5487             "QUOTE">"<span class="emphasis"><i class=
5488             "EMPHASIS">ads</i></span>l.some-provider.net."</span> So here
5489             come some well-known exceptions to the <tt class="LITERAL">+<a
5490             href="actions-file.html#BLOCK">block</a></tt> section above.
5491           </p>
5492           <p>
5493             Note that these are exceptions to exceptions from the default!
5494             Consider the URL <span class=
5495             "QUOTE">"downloads.sourcefroge.net"</span>: Initially, all
5496             actions are deactivated, so it wouldn't get blocked. Then comes
5497             the defaults section, which matches the URL, but just deactivates
5498             the <tt class="LITERAL"><a href=
5499             "actions-file.html#BLOCK">block</a></tt> action once again. Then
5500             it matches <tt class="LITERAL">.*ads.</tt>, an exception to the
5501             general non-blocking policy, and suddenly <tt class="LITERAL"><a
5502             href="actions-file.html#BLOCK">+block</a></tt> applies. And now,
5503             it'll match <tt class="LITERAL">.*loads.</tt>, where <tt class=
5504             "LITERAL"><a href="actions-file.html#BLOCK">-block</a></tt>
5505             applies, so (unless it matches <span class="emphasis"><i class=
5506             "EMPHASIS">again</i></span> further down) it ends up with no <tt
5507             class="LITERAL"><a href="actions-file.html#BLOCK">block</a></tt>
5508             action applying.
5509           </p>
5510           <p>
5511           </p>
5512           <table border="0" bgcolor="#E0E0E0" width="100%">
5513             <tr>
5514               <td>
5515 <pre class="SCREEN">
5516 ##########################################################################
5517 # Save some innocent victims of the above generic block patterns:
5518 ##########################################################################
5519
5520 # By domain:
5521 #
5522 { -<a href="actions-file.html#BLOCK">block</a> }
5523 adv[io]*.  # (for advogato.org and advice.*)
5524 adsl.      # (has nothing to do with ads)
5525 adobe.     # (has nothing to do with ads either)
5526 ad[ud]*.   # (adult.* and add.*)
5527 .edu       # (universities don't host banners (yet!))
5528 .*loads.   # (downloads, uploads etc)
5529
5530 # By path:
5531 #
5532 /.*loads/
5533
5534 # Site-specific:
5535 #
5536 www.globalintersec.com/adv # (adv = advanced)
5537 www.ugu.com/sui/ugu/adv
5538 </pre>
5539               </td>
5540             </tr>
5541           </table>
5542
5543           <p>
5544             Filtering source code can have nasty side effects, so make an
5545             exception for our friends at sourceforge.net, and all paths with
5546             <span class="QUOTE">"cvs"</span> in them. Note that <tt class=
5547             "LITERAL">-<a href="actions-file.html#FILTER">filter</a></tt>
5548             disables <span class="emphasis"><i class=
5549             "EMPHASIS">all</i></span> filters in one fell swoop!
5550           </p>
5551           <p>
5552           </p>
5553           <table border="0" bgcolor="#E0E0E0" width="100%">
5554             <tr>
5555               <td>
5556 <pre class="SCREEN">
5557 # Don't filter code!
5558 #
5559 { -<a href="actions-file.html#FILTER">filter</a> }
5560 /(.*/)?cvs
5561 bugzilla.
5562 developer.
5563 wiki.
5564 .sourceforge.net
5565 </pre>
5566               </td>
5567             </tr>
5568           </table>
5569
5570           <p>
5571             The actual <tt class="FILENAME">default.action</tt> is of course
5572             much more comprehensive, but we hope this example made clear how
5573             it works.
5574           </p>
5575         </div>
5576         <div class="SECT3">
5577           <h3 class="SECT3">
5578             <a name="AEN4748">8.7.3. user.action</a>
5579           </h3>
5580           <p>
5581             So far we are painting with a broad brush by setting general
5582             policies, which would be a reasonable starting point for many
5583             people. Now, you might want to be more specific and have
5584             customized rules that are more suitable to your personal habits
5585             and preferences. These would be for narrowly defined situations
5586             like your ISP or your bank, and should be placed in <tt class=
5587             "FILENAME">user.action</tt>, which is parsed after all other
5588             actions files and hence has the last word, over-riding any
5589             previously defined actions. <tt class="FILENAME">user.action</tt>
5590             is also a <span class="emphasis"><i class=
5591             "EMPHASIS">safe</i></span> place for your personal settings,
5592             since <tt class="FILENAME">default.action</tt> is actively
5593             maintained by the <span class="APPLICATION">Privoxy</span>
5594             developers and you'll probably want to install updated versions
5595             from time to time.
5596           </p>
5597           <p>
5598             So let's look at a few examples of things that one might
5599             typically do in <tt class="FILENAME">user.action</tt>:
5600           </p>
5601           <p>
5602           </p>
5603           <table border="0" bgcolor="#E0E0E0" width="100%">
5604             <tr>
5605               <td>
5606 <pre class="SCREEN">
5607 # My user.action file. &lt;fred@example.com&gt;
5608 </pre>
5609               </td>
5610             </tr>
5611           </table>
5612
5613           <p>
5614             As <a href="actions-file.html#ALIASES">aliases</a> are local to
5615             the actions file that they are defined in, you can't use the ones
5616             from <tt class="FILENAME">default.action</tt>, unless you repeat
5617             them here:
5618           </p>
5619           <p>
5620           </p>
5621           <table border="0" bgcolor="#E0E0E0" width="100%">
5622             <tr>
5623               <td>
5624 <pre class="SCREEN">
5625 # Aliases are local to the file they are defined in.
5626 # (Re-)define aliases for this file:
5627 #
5628 {{alias}}
5629 #
5630 # These aliases just save typing later, and the alias names should
5631 # be self explanatory.
5632 #
5633 +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
5634 -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
5635  allow-all-cookies  = -crunch-all-cookies -session-cookies-only
5636  allow-popups       = -filter{all-popups}
5637 +block-as-image     = +block{Blocked as image.} +handle-as-image
5638 -block-as-image     = -block
5639
5640 # These aliases define combinations of actions that are useful for
5641 # certain types of sites:
5642 #
5643 fragile     = -block -crunch-all-cookies -filter -fast-redirects -hide-referrer
5644 shop        = -crunch-all-cookies allow-popups
5645
5646 # Allow ads for selected useful free sites:
5647 #
5648 allow-ads   = -block -filter{banners-by-size} -filter{banners-by-link}
5649
5650 # Alias for specific file types that are text, but might have conflicting
5651 # MIME types. We want the browser to force these to be text documents.
5652 handle-as-text = -<a href="actions-file.html#FILTER">filter</a> +-<a href=
5653 "actions-file.html#CONTENT-TYPE-OVERWRITE">content-type-overwrite{text/plain}</a> +-<a
5654  href="actions-file.html#FORCE-TEXT-MODE">force-text-mode</a> -<a href=
5655 "actions-file.html#HIDE-CONTENT-DISPOSITION">hide-content-disposition</a>
5656 </pre>
5657               </td>
5658             </tr>
5659           </table>
5660           &#13;<br>
5661
5662           <p>
5663             Say you have accounts on some sites that you visit regularly, and
5664             you don't want to have to log in manually each time. So you'd
5665             like to allow persistent cookies for these sites. The <tt class=
5666             "LITERAL">allow-all-cookies</tt> alias defined above does exactly
5667             that, i.e. it disables crunching of cookies in any direction, and
5668             the processing of cookies to make them only temporary.
5669           </p>
5670           <p>
5671           </p>
5672           <table border="0" bgcolor="#E0E0E0" width="100%">
5673             <tr>
5674               <td>
5675 <pre class="SCREEN">
5676 { allow-all-cookies }
5677  sourceforge.net
5678  .yahoo.com
5679  .msdn.microsoft.com
5680  .redhat.com
5681 </pre>
5682               </td>
5683             </tr>
5684           </table>
5685
5686           <p>
5687             Your bank is allergic to some filter, but you don't know which,
5688             so you disable them all:
5689           </p>
5690           <p>
5691           </p>
5692           <table border="0" bgcolor="#E0E0E0" width="100%">
5693             <tr>
5694               <td>
5695 <pre class="SCREEN">
5696 { -<a href="actions-file.html#FILTER">filter</a> }
5697  .your-home-banking-site.com
5698 </pre>
5699               </td>
5700             </tr>
5701           </table>
5702
5703           <p>
5704             Some file types you may not want to filter for various reasons:
5705           </p>
5706           <p>
5707           </p>
5708           <table border="0" bgcolor="#E0E0E0" width="100%">
5709             <tr>
5710               <td>
5711 <pre class="SCREEN">
5712 # Technical documentation is likely to contain strings that might
5713 # erroneously get altered by the JavaScript-oriented filters:
5714 #
5715 .tldp.org
5716 /(.*/)?selfhtml/
5717
5718 # And this stupid host sends streaming video with a wrong MIME type,
5719 # so that Privoxy thinks it is getting HTML and starts filtering:
5720 #
5721 stupid-server.example.com/
5722 </pre>
5723               </td>
5724             </tr>
5725           </table>
5726
5727           <p>
5728             Example of a simple <a href="actions-file.html#BLOCK">block</a>
5729             action. Say you've seen an ad on your favourite page on
5730             example.com that you want to get rid of. You have right-clicked
5731             the image, selected <span class="QUOTE">"copy image
5732             location"</span> and pasted the URL below while removing the
5733             leading http://, into a <tt class="LITERAL">{ +block{} }</tt>
5734             section. Note that <tt class="LITERAL">{ +handle-as-image }</tt>
5735             need not be specified, since all URLs ending in <tt class=
5736             "LITERAL">.gif</tt> will be tagged as images by the general rules
5737             as set in default.action anyway:
5738           </p>
5739           <p>
5740           </p>
5741           <table border="0" bgcolor="#E0E0E0" width="100%">
5742             <tr>
5743               <td>
5744 <pre class="SCREEN">
5745 { +<a href="actions-file.html#BLOCK">block</a>{Nasty ads.} }
5746  www.example.com/nasty-ads/sponsor\.gif
5747  another.example.net/more/junk/here/
5748 </pre>
5749               </td>
5750             </tr>
5751           </table>
5752
5753           <p>
5754             The URLs of dynamically generated banners, especially from large
5755             banner farms, often don't use the well-known image file name
5756             extensions, which makes it impossible for <span class=
5757             "APPLICATION">Privoxy</span> to guess the file type just by
5758             looking at the URL. You can use the <tt class=
5759             "LITERAL">+block-as-image</tt> alias defined above for these
5760             cases. Note that objects which match this rule but then turn out
5761             NOT to be an image are typically rendered as a <span class=
5762             "QUOTE">"broken image"</span> icon by the browser. Use
5763             cautiously.
5764           </p>
5765           <p>
5766           </p>
5767           <table border="0" bgcolor="#E0E0E0" width="100%">
5768             <tr>
5769               <td>
5770 <pre class="SCREEN">
5771 { +block-as-image }
5772  .doubleclick.net
5773  .fastclick.net
5774  /Realmedia/ads/
5775  ar.atwola.com/
5776 </pre>
5777               </td>
5778             </tr>
5779           </table>
5780
5781           <p>
5782             Now you noticed that the default configuration breaks Forbes
5783             Magazine, but you were too lazy to find out which action is the
5784             culprit, and you were again too lazy to give <a href=
5785             "contact.html">feedback</a>, so you just used the <tt class=
5786             "LITERAL">fragile</tt> alias on the site, and -- <span class=
5787             "emphasis"><i class="EMPHASIS">whoa!</i></span> -- it worked. The
5788             <tt class="LITERAL">fragile</tt> aliases disables those actions
5789             that are most likely to break a site. Also, good for testing
5790             purposes to see if it is <span class="APPLICATION">Privoxy</span>
5791             that is causing the problem or not. We later find other regular
5792             sites that misbehave, and add those to our personalized list of
5793             troublemakers:
5794           </p>
5795           <table border="0" bgcolor="#E0E0E0" width="100%">
5796             <tr>
5797               <td>
5798 <pre class="SCREEN">
5799 { fragile }
5800  .forbes.com
5801  webmail.example.com
5802  .mybank.com
5803 </pre>
5804               </td>
5805             </tr>
5806           </table>
5807
5808           <p>
5809             You like the <span class="QUOTE">"fun"</span> text replacements
5810             in <tt class="FILENAME">default.filter</tt>, but it is disabled
5811             in the distributed actions file. So you'd like to turn it on in
5812             your private, update-safe config, once and for all:
5813           </p>
5814           <table border="0" bgcolor="#E0E0E0" width="100%">
5815             <tr>
5816               <td>
5817 <pre class="SCREEN">
5818 { +<a href="actions-file.html#FILTER-FUN">filter{fun}</a> }
5819  / # For ALL sites!
5820 </pre>
5821               </td>
5822             </tr>
5823           </table>
5824
5825           <p>
5826             Note that the above is not really a good idea: There are
5827             exceptions to the filters in <tt class=
5828             "FILENAME">default.action</tt> for things that really shouldn't
5829             be filtered, like code on CVS-&gt;Web interfaces. Since <tt
5830             class="FILENAME">user.action</tt> has the last word, these
5831             exceptions won't be valid for the <span class=
5832             "QUOTE">"fun"</span> filtering specified here.
5833           </p>
5834           <p>
5835             You might also worry about how your favourite free websites are
5836             funded, and find that they rely on displaying banner
5837             advertisements to survive. So you might want to specifically
5838             allow banners for those sites that you feel provide value to you:
5839           </p>
5840           <table border="0" bgcolor="#E0E0E0" width="100%">
5841             <tr>
5842               <td>
5843 <pre class="SCREEN">
5844 { allow-ads }
5845  .sourceforge.net
5846  .slashdot.org
5847  .osdn.net
5848 </pre>
5849               </td>
5850             </tr>
5851           </table>
5852
5853           <p>
5854             Note that <tt class="LITERAL">allow-ads</tt> has been aliased to
5855             <tt class="LITERAL">-<a href=
5856             "actions-file.html#BLOCK">block</a></tt>, <tt class="LITERAL">-<a
5857             href=
5858             "actions-file.html#FILTER-BANNERS-BY-SIZE">filter{banners-by-size}</a></tt>,
5859             and <tt class="LITERAL">-<a href=
5860             "actions-file.html#FILTER-BANNERS-BY-LINK">filter{banners-by-link}</a></tt>
5861             above.
5862           </p>
5863           <p>
5864             Invoke another alias here to force an over-ride of the MIME type
5865             <tt class="LITERAL">application/x-sh</tt> which typically would
5866             open a download type dialog. In my case, I want to look at the
5867             shell script, and then I can save it should I choose to.
5868           </p>
5869           <table border="0" bgcolor="#E0E0E0" width="100%">
5870             <tr>
5871               <td>
5872 <pre class="SCREEN">
5873 { handle-as-text }
5874  /.*\.sh$
5875 </pre>
5876               </td>
5877             </tr>
5878           </table>
5879
5880           <p>
5881             <tt class="FILENAME">user.action</tt> is generally the best place
5882             to define exceptions and additions to the default policies of <tt
5883             class="FILENAME">default.action</tt>. Some actions are safe to
5884             have their default policies set here though. So let's set a
5885             default policy to have a <span class="QUOTE">"blank"</span> image
5886             as opposed to the checkerboard pattern for <span class=
5887             "emphasis"><i class="EMPHASIS">ALL</i></span> sites. <span class=
5888             "QUOTE">"/"</span> of course matches all URL paths and patterns:
5889           </p>
5890           <table border="0" bgcolor="#E0E0E0" width="100%">
5891             <tr>
5892               <td>
5893 <pre class="SCREEN">
5894 { +<a href=
5895 "actions-file.html#SET-IMAGE-BLOCKER">set-image-blocker{blank}</a> }
5896 / # ALL sites
5897 </pre>
5898               </td>
5899             </tr>
5900           </table>
5901         </div>
5902       </div>
5903     </div>
5904     <div class="NAVFOOTER">
5905       <hr width="100%" class="c1">
5906       <table summary="Footer navigation table" width="100%" border="0"
5907       cellpadding="0" cellspacing="0">
5908         <tr>
5909           <td width="33%" align="left" valign="top">
5910             <a href="config.html" accesskey="P">Prev</a>
5911           </td>
5912           <td width="34%" align="center" valign="top">
5913             <a href="index.html" accesskey="H">Home</a>
5914           </td>
5915           <td width="33%" align="right" valign="top">
5916             <a href="filter-file.html" accesskey="N">Next</a>
5917           </td>
5918         </tr>
5919         <tr>
5920           <td width="33%" align="left" valign="top">
5921             The Main Configuration File
5922           </td>
5923           <td width="34%" align="center" valign="top">
5924             &nbsp;
5925           </td>
5926           <td width="33%" align="right" valign="top">
5927             Filter Files
5928           </td>
5929         </tr>
5930       </table>
5931     </div>
5932   </body>
5933 </html>
5934