doc/webserver/user-manual/config.html

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  24         <th colspan="3" align="center">Privoxy 3.0.21 User Manual</th>
  25       </tr>
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  40   <div class="SECT1">
  41     <h1 class="SECT1"><a name="CONFIG" id="CONFIG">7. The Main Configuration
  42     File</a></h1>
  43
  44     <p>By default, the main configuration file is named <tt class=
  45     "FILENAME">config</tt>, with the exception of Windows, where it is named
  46     <tt class="FILENAME">config.txt</tt>. Configuration lines consist of an
  47     initial keyword followed by a list of values, all separated by whitespace
  48     (any number of spaces or tabs). For example:</p>
  49
  50     <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
  51     "emphasis"><i class="EMPHASIS">confdir /etc/privoxy</i></span></tt></p>
  52
  53     <p>Assigns the value <tt class="LITERAL">/etc/privoxy</tt> to the option
  54     <tt class="LITERAL">confdir</tt> and thus indicates that the
  55     configuration directory is named <span class=
  56     "QUOTE">"/etc/privoxy/"</span>.</p>
  57
  58     <p>All options in the config file except for <tt class=
  59     "LITERAL">confdir</tt> and <tt class="LITERAL">logdir</tt> are optional.
  60     Watch out in the below description for what happens if you leave them
  61     unset.</p>
  62
  63     <p>The main config file controls all aspects of <span class=
  64     "APPLICATION">Privoxy</span>'s operation that are not location dependent
  65     (i.e. they apply universally, no matter where you may be surfing). Like
  66     the filter and action files, the config file is a plain text file and can
  67     be modified with a text editor like emacs, vim or notepad.exe.</p>
  68
  69     <div class="SECT2">
  70       <h2 class="SECT2"><a name="LOCAL-SET-UP" id="LOCAL-SET-UP">7.1. Local
  71       Set-up Documentation</a></h2>
  72
  73       <p>If you intend to operate <span class="APPLICATION">Privoxy</span>
  74       for more users than just yourself, it might be a good idea to let them
  75       know how to reach you, what you block and why you do that, your
  76       policies, etc.</p>
  77
  78       <div class="SECT3">
  79         <h4 class="SECT3"><a name="USER-MANUAL" id="USER-MANUAL">7.1.1.
  80         user-manual</a></h4>
  81
  82         <div class="VARIABLELIST">
  83           <dl>
  84             <dt>Specifies:</dt>
  85
  86             <dd>
  87               <p>Location of the <span class="APPLICATION">Privoxy</span>
  88               User Manual.</p>
  89             </dd>
  90
  91             <dt>Type of value:</dt>
  92
  93             <dd>
  94               <p>A fully qualified URI</p>
  95             </dd>
  96
  97             <dt>Default value:</dt>
  98
  99             <dd>
 100               <p><span class="emphasis"><i class=
 101               "EMPHASIS">Unset</i></span></p>
 102             </dd>
 103
 104             <dt>Effect if unset:</dt>
 105
 106             <dd>
 107               <p><a href="http://www.privoxy.org/user-manual/" target=
 108               "_top">http://www.privoxy.org/<tt class=
 109               "REPLACEABLE"><i>version</i></tt>/user-manual/</a> will be
 110               used, where <tt class="REPLACEABLE"><i>version</i></tt> is the
 111               <span class="APPLICATION">Privoxy</span> version.</p>
 112             </dd>
 113
 114             <dt>Notes:</dt>
 115
 116             <dd>
 117               <p>The User Manual URI is the single best source of information
 118               on <span class="APPLICATION">Privoxy</span>, and is used for
 119               help links from some of the internal CGI pages. The manual
 120               itself is normally packaged with the binary distributions, so
 121               you probably want to set this to a locally installed copy.</p>
 122
 123               <p>Examples:</p>
 124
 125               <p>The best all purpose solution is simply to put the full
 126               local <tt class="LITERAL">PATH</tt> to where the <i class=
 127               "CITETITLE">User Manual</i> is located:</p>
 128
 129               <table border="0" bgcolor="#E0E0E0" width="90%">
 130                 <tr>
 131                   <td>
 132                     <pre class="SCREEN">
 133   user-manual  /usr/share/doc/privoxy/user-manual
 134 </pre>
 135                   </td>
 136                 </tr>
 137               </table>
 138
 139               <p>The User Manual is then available to anyone with access to
 140               <span class="APPLICATION">Privoxy</span>, by following the
 141               built-in URL: <tt class=
 142               "LITERAL">http://config.privoxy.org/user-manual/</tt> (or the
 143               shortcut: <tt class=
 144               "LITERAL">http://p.p/user-manual/</tt>).</p>
 145
 146               <p>If the documentation is not on the local system, it can be
 147               accessed from a remote server, as:</p>
 148
 149               <table border="0" bgcolor="#E0E0E0" width="90%">
 150                 <tr>
 151                   <td>
 152                     <pre class="SCREEN">
 153   user-manual  http://example.com/privoxy/user-manual/
 154 </pre>
 155                   </td>
 156                 </tr>
 157               </table>
 158
 159               <div class="WARNING">
 160                 <table class="WARNING" border="1" width="90%">
 161                   <tr>
 162                     <td align="center"><b>Warning</b></td>
 163                   </tr>
 164
 165                   <tr>
 166                     <td align="left">
 167                       <p>If set, this option should be <span class=
 168                       "emphasis"><i class="EMPHASIS">the first option in the
 169                       config file</i></span>, because it is used while the
 170                       config file is being read on start-up.</p>
 171                     </td>
 172                   </tr>
 173                 </table>
 174               </div>
 175             </dd>
 176           </dl>
 177         </div>
 178       </div>
 179
 180       <div class="SECT3">
 181         <h4 class="SECT3"><a name="TRUST-INFO-URL" id="TRUST-INFO-URL">7.1.2.
 182         trust-info-url</a></h4>
 183
 184         <div class="VARIABLELIST">
 185           <dl>
 186             <dt>Specifies:</dt>
 187
 188             <dd>
 189               <p>A URL to be displayed in the error page that users will see
 190               if access to an untrusted page is denied.</p>
 191             </dd>
 192
 193             <dt>Type of value:</dt>
 194
 195             <dd>
 196               <p>URL</p>
 197             </dd>
 198
 199             <dt>Default value:</dt>
 200
 201             <dd>
 202               <p><span class="emphasis"><i class=
 203               "EMPHASIS">Unset</i></span></p>
 204             </dd>
 205
 206             <dt>Effect if unset:</dt>
 207
 208             <dd>
 209               <p>No links are displayed on the "untrusted" error page.</p>
 210             </dd>
 211
 212             <dt>Notes:</dt>
 213
 214             <dd>
 215               <p>The value of this option only matters if the experimental
 216               trust mechanism has been activated. (See <a href=
 217               "config.html#TRUSTFILE"><span class="emphasis"><i class=
 218               "EMPHASIS">trustfile</i></span></a> below.)</p>
 219
 220               <p>If you use the trust mechanism, it is a good idea to write
 221               up some on-line documentation about your trust policy and to
 222               specify the URL(s) here. Use multiple times for multiple
 223               URLs.</p>
 224
 225               <p>The URL(s) should be added to the trustfile as well, so
 226               users don't end up locked out from the information on why they
 227               were locked out in the first place!</p>
 228             </dd>
 229           </dl>
 230         </div>
 231       </div>
 232
 233       <div class="SECT3">
 234         <h4 class="SECT3"><a name="ADMIN-ADDRESS" id="ADMIN-ADDRESS">7.1.3.
 235         admin-address</a></h4>
 236
 237         <div class="VARIABLELIST">
 238           <dl>
 239             <dt>Specifies:</dt>
 240
 241             <dd>
 242               <p>An email address to reach the <span class=
 243               "APPLICATION">Privoxy</span> administrator.</p>
 244             </dd>
 245
 246             <dt>Type of value:</dt>
 247
 248             <dd>
 249               <p>Email address</p>
 250             </dd>
 251
 252             <dt>Default value:</dt>
 253
 254             <dd>
 255               <p><span class="emphasis"><i class=
 256               "EMPHASIS">Unset</i></span></p>
 257             </dd>
 258
 259             <dt>Effect if unset:</dt>
 260
 261             <dd>
 262               <p>No email address is displayed on error pages and the CGI
 263               user interface.</p>
 264             </dd>
 265
 266             <dt>Notes:</dt>
 267
 268             <dd>
 269               <p>If both <tt class="LITERAL">admin-address</tt> and
 270               <tt class="LITERAL">proxy-info-url</tt> are unset, the whole
 271               "Local Privoxy Support" box on all generated pages will not be
 272               shown.</p>
 273             </dd>
 274           </dl>
 275         </div>
 276       </div>
 277
 278       <div class="SECT3">
 279         <h4 class="SECT3"><a name="PROXY-INFO-URL" id="PROXY-INFO-URL">7.1.4.
 280         proxy-info-url</a></h4>
 281
 282         <div class="VARIABLELIST">
 283           <dl>
 284             <dt>Specifies:</dt>
 285
 286             <dd>
 287               <p>A URL to documentation about the local <span class=
 288               "APPLICATION">Privoxy</span> setup, configuration or
 289               policies.</p>
 290             </dd>
 291
 292             <dt>Type of value:</dt>
 293
 294             <dd>
 295               <p>URL</p>
 296             </dd>
 297
 298             <dt>Default value:</dt>
 299
 300             <dd>
 301               <p><span class="emphasis"><i class=
 302               "EMPHASIS">Unset</i></span></p>
 303             </dd>
 304
 305             <dt>Effect if unset:</dt>
 306
 307             <dd>
 308               <p>No link to local documentation is displayed on error pages
 309               and the CGI user interface.</p>
 310             </dd>
 311
 312             <dt>Notes:</dt>
 313
 314             <dd>
 315               <p>If both <tt class="LITERAL">admin-address</tt> and
 316               <tt class="LITERAL">proxy-info-url</tt> are unset, the whole
 317               "Local Privoxy Support" box on all generated pages will not be
 318               shown.</p>
 319
 320               <p>This URL shouldn't be blocked ;-)</p>
 321             </dd>
 322           </dl>
 323         </div>
 324       </div>
 325     </div>
 326
 327     <div class="SECT2">
 328       <h2 class="SECT2"><a name="CONF-LOG-LOC" id="CONF-LOG-LOC">7.2.
 329       Configuration and Log File Locations</a></h2>
 330
 331       <p><span class="APPLICATION">Privoxy</span> can (and normally does) use
 332       a number of other files for additional configuration, help and logging.
 333       This section of the configuration file tells <span class=
 334       "APPLICATION">Privoxy</span> where to find those other files.</p>
 335
 336       <p>The user running <span class="APPLICATION">Privoxy</span>, must have
 337       read permission for all configuration files, and write permission to
 338       any files that would be modified, such as log files and actions
 339       files.</p>
 340
 341       <div class="SECT3">
 342         <h4 class="SECT3"><a name="CONFDIR" id="CONFDIR">7.2.1.
 343         confdir</a></h4>
 344
 345         <div class="VARIABLELIST">
 346           <dl>
 347             <dt>Specifies:</dt>
 348
 349             <dd>
 350               <p>The directory where the other configuration files are
 351               located.</p>
 352             </dd>
 353
 354             <dt>Type of value:</dt>
 355
 356             <dd>
 357               <p>Path name</p>
 358             </dd>
 359
 360             <dt>Default value:</dt>
 361
 362             <dd>
 363               <p>/etc/privoxy (Unix) <span class="emphasis"><i class=
 364               "EMPHASIS">or</i></span> <span class=
 365               "APPLICATION">Privoxy</span> installation dir (Windows)</p>
 366             </dd>
 367
 368             <dt>Effect if unset:</dt>
 369
 370             <dd>
 371               <p><span class="emphasis"><i class=
 372               "EMPHASIS">Mandatory</i></span></p>
 373             </dd>
 374
 375             <dt>Notes:</dt>
 376
 377             <dd>
 378               <p>No trailing <span class="QUOTE">"<tt class=
 379               "LITERAL">/</tt>"</span>, please.</p>
 380             </dd>
 381           </dl>
 382         </div>
 383       </div>
 384
 385       <div class="SECT3">
 386         <h4 class="SECT3"><a name="TEMPLDIR" id="TEMPLDIR">7.2.2.
 387         templdir</a></h4>
 388
 389         <div class="VARIABLELIST">
 390           <dl>
 391             <dt>Specifies:</dt>
 392
 393             <dd>
 394               <p>An alternative directory where the templates are loaded
 395               from.</p>
 396             </dd>
 397
 398             <dt>Type of value:</dt>
 399
 400             <dd>
 401               <p>Path name</p>
 402             </dd>
 403
 404             <dt>Default value:</dt>
 405
 406             <dd>
 407               <p>unset</p>
 408             </dd>
 409
 410             <dt>Effect if unset:</dt>
 411
 412             <dd>
 413               <p>The templates are assumed to be located in
 414               confdir/template.</p>
 415             </dd>
 416
 417             <dt>Notes:</dt>
 418
 419             <dd>
 420               <p><span class="APPLICATION">Privoxy's</span> original
 421               templates are usually overwritten with each update. Use this
 422               option to relocate customized templates that should be kept. As
 423               template variables might change between updates, you shouldn't
 424               expect templates to work with <span class=
 425               "APPLICATION">Privoxy</span> releases other than the one they
 426               were part of, though.</p>
 427             </dd>
 428           </dl>
 429         </div>
 430       </div>
 431
 432       <div class="SECT3">
 433         <h4 class="SECT3"><a name="LOGDIR" id="LOGDIR">7.2.3. logdir</a></h4>
 434
 435         <div class="VARIABLELIST">
 436           <dl>
 437             <dt>Specifies:</dt>
 438
 439             <dd>
 440               <p>The directory where all logging takes place (i.e. where the
 441               <tt class="FILENAME">logfile</tt> is located).</p>
 442             </dd>
 443
 444             <dt>Type of value:</dt>
 445
 446             <dd>
 447               <p>Path name</p>
 448             </dd>
 449
 450             <dt>Default value:</dt>
 451
 452             <dd>
 453               <p>/var/log/privoxy (Unix) <span class="emphasis"><i class=
 454               "EMPHASIS">or</i></span> <span class=
 455               "APPLICATION">Privoxy</span> installation dir (Windows)</p>
 456             </dd>
 457
 458             <dt>Effect if unset:</dt>
 459
 460             <dd>
 461               <p><span class="emphasis"><i class=
 462               "EMPHASIS">Mandatory</i></span></p>
 463             </dd>
 464
 465             <dt>Notes:</dt>
 466
 467             <dd>
 468               <p>No trailing <span class="QUOTE">"<tt class=
 469               "LITERAL">/</tt>"</span>, please.</p>
 470             </dd>
 471           </dl>
 472         </div>
 473       </div>
 474
 475       <div class="SECT3">
 476         <h4 class="SECT3"><a name="ACTIONSFILE" id="ACTIONSFILE">7.2.4.
 477         actionsfile</a></h4><a name="DEFAULT.ACTION" id=
 478         "DEFAULT.ACTION"></a><a name="STANDARD.ACTION" id=
 479         "STANDARD.ACTION"></a><a name="USER.ACTION" id="USER.ACTION"></a>
 480
 481         <div class="VARIABLELIST">
 482           <dl>
 483             <dt>Specifies:</dt>
 484
 485             <dd>
 486               <p>The <a href="actions-file.html">actions file(s)</a> to
 487               use</p>
 488             </dd>
 489
 490             <dt>Type of value:</dt>
 491
 492             <dd>
 493               <p>Complete file name, relative to <tt class=
 494               "LITERAL">confdir</tt></p>
 495             </dd>
 496
 497             <dt>Default values:</dt>
 498
 499             <dd>
 500               <table border="0">
 501                 <tbody>
 502                   <tr>
 503                     <td>
 504                       <p class="LITERALLAYOUT">
 505                       &nbsp;&nbsp;match-all.action&nbsp;#&nbsp;Actions&nbsp;that&nbsp;are&nbsp;applied&nbsp;to&nbsp;all&nbsp;sites&nbsp;and&nbsp;maybe&nbsp;overruled&nbsp;later&nbsp;on.</p>
 506                     </td>
 507                   </tr>
 508
 509                   <tr>
 510                     <td>
 511                       <p class="LITERALLAYOUT">
 512                       &nbsp;&nbsp;default.action&nbsp;&nbsp;&nbsp;#&nbsp;Main&nbsp;actions&nbsp;file</p>
 513                     </td>
 514                   </tr>
 515
 516                   <tr>
 517                     <td>
 518                       <p class="LITERALLAYOUT">
 519                       &nbsp;&nbsp;user.action&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#&nbsp;User&nbsp;customizations</p>
 520                     </td>
 521                   </tr>
 522                 </tbody>
 523               </table>
 524             </dd>
 525
 526             <dt>Effect if unset:</dt>
 527
 528             <dd>
 529               <p>No actions are taken at all. More or less neutral
 530               proxying.</p>
 531             </dd>
 532
 533             <dt>Notes:</dt>
 534
 535             <dd>
 536               <p>Multiple <tt class="LITERAL">actionsfile</tt> lines are
 537               permitted, and are in fact recommended!</p>
 538
 539               <p>The default values are <tt class=
 540               "FILENAME">default.action</tt>, which is the <span class=
 541               "QUOTE">"main"</span> actions file maintained by the
 542               developers, and <tt class="FILENAME">user.action</tt>, where
 543               you can make your personal additions.</p>
 544
 545               <p>Actions files contain all the per site and per URL
 546               configuration for ad blocking, cookie management, privacy
 547               considerations, etc. There is no point in using <span class=
 548               "APPLICATION">Privoxy</span> without at least one actions
 549               file.</p>
 550
 551               <p>Note that since Privoxy 3.0.7, the complete filename,
 552               including the <span class="QUOTE">".action"</span> extension
 553               has to be specified. The syntax change was necessary to be
 554               consistent with the other file options and to allow previously
 555               forbidden characters.</p>
 556             </dd>
 557           </dl>
 558         </div>
 559       </div>
 560
 561       <div class="SECT3">
 562         <h4 class="SECT3"><a name="FILTERFILE" id="FILTERFILE">7.2.5.
 563         filterfile</a></h4><a name="DEFAULT.FILTER" id="DEFAULT.FILTER"></a>
 564
 565         <div class="VARIABLELIST">
 566           <dl>
 567             <dt>Specifies:</dt>
 568
 569             <dd>
 570               <p>The <a href="filter-file.html">filter file(s)</a> to use</p>
 571             </dd>
 572
 573             <dt>Type of value:</dt>
 574
 575             <dd>
 576               <p>File name, relative to <tt class="LITERAL">confdir</tt></p>
 577             </dd>
 578
 579             <dt>Default value:</dt>
 580
 581             <dd>
 582               <p>default.filter (Unix) <span class="emphasis"><i class=
 583               "EMPHASIS">or</i></span> default.filter.txt (Windows)</p>
 584             </dd>
 585
 586             <dt>Effect if unset:</dt>
 587
 588             <dd>
 589               <p>No textual content filtering takes place, i.e. all
 590               <tt class="LITERAL">+<a href=
 591               "actions-file.html#FILTER">filter</a>{<tt class=
 592               "REPLACEABLE"><i>name</i></tt>}</tt> actions in the actions
 593               files are turned neutral.</p>
 594             </dd>
 595
 596             <dt>Notes:</dt>
 597
 598             <dd>
 599               <p>Multiple <tt class="LITERAL">filterfile</tt> lines are
 600               permitted.</p>
 601
 602               <p>The <a href="filter-file.html">filter files</a> contain
 603               content modification rules that use <a href=
 604               "appendix.html#REGEX">regular expressions</a>. These rules
 605               permit powerful changes on the content of Web pages, and
 606               optionally the headers as well, e.g., you could try to disable
 607               your favorite JavaScript annoyances, re-write the actual
 608               displayed text, or just have some fun playing buzzword bingo
 609               with web pages.</p>
 610
 611               <p>The <tt class="LITERAL">+<a href=
 612               "actions-file.html#FILTER">filter</a>{<tt class=
 613               "REPLACEABLE"><i>name</i></tt>}</tt> actions rely on the
 614               relevant filter (<tt class="REPLACEABLE"><i>name</i></tt>) to
 615               be defined in a filter file!</p>
 616
 617               <p>A pre-defined filter file called <tt class=
 618               "FILENAME">default.filter</tt> that contains a number of useful
 619               filters for common problems is included in the distribution.
 620               See the section on the <tt class="LITERAL"><a href=
 621               "actions-file.html#FILTER">filter</a></tt> action for a
 622               list.</p>
 623
 624               <p>It is recommended to place any locally adapted filters into
 625               a separate file, such as <tt class=
 626               "FILENAME">user.filter</tt>.</p>
 627             </dd>
 628           </dl>
 629         </div>
 630       </div>
 631
 632       <div class="SECT3">
 633         <h4 class="SECT3"><a name="LOGFILE" id="LOGFILE">7.2.6.
 634         logfile</a></h4>
 635
 636         <div class="VARIABLELIST">
 637           <dl>
 638             <dt>Specifies:</dt>
 639
 640             <dd>
 641               <p>The log file to use</p>
 642             </dd>
 643
 644             <dt>Type of value:</dt>
 645
 646             <dd>
 647               <p>File name, relative to <tt class="LITERAL">logdir</tt></p>
 648             </dd>
 649
 650             <dt>Default value:</dt>
 651
 652             <dd>
 653               <p><span class="emphasis"><i class="EMPHASIS">Unset (commented
 654               out)</i></span>. When activated: logfile (Unix) <span class=
 655               "emphasis"><i class="EMPHASIS">or</i></span> privoxy.log
 656               (Windows).</p>
 657             </dd>
 658
 659             <dt>Effect if unset:</dt>
 660
 661             <dd>
 662               <p>No logfile is written.</p>
 663             </dd>
 664
 665             <dt>Notes:</dt>
 666
 667             <dd>
 668               <p>The logfile is where all logging and error messages are
 669               written. The level of detail and number of messages are set
 670               with the <tt class="LITERAL">debug</tt> option (see below). The
 671               logfile can be useful for tracking down a problem with
 672               <span class="APPLICATION">Privoxy</span> (e.g., it's not
 673               blocking an ad you think it should block) and it can help you
 674               to monitor what your browser is doing.</p>
 675
 676               <p>Depending on the debug options below, the logfile may be a
 677               privacy risk if third parties can get access to it. As most
 678               users will never look at it, <span class=
 679               "APPLICATION">Privoxy</span> 3.0.7 and later only log fatal
 680               errors by default.</p>
 681
 682               <p>For most troubleshooting purposes, you will have to change
 683               that, please refer to the debugging section for details.</p>
 684
 685               <p>Your logfile will grow indefinitely, and you will probably
 686               want to periodically remove it. On Unix systems, you can do
 687               this with a cron job (see <span class="QUOTE">"man
 688               cron"</span>).</p>
 689
 690               <p>Any log files must be writable by whatever user <span class=
 691               "APPLICATION">Privoxy</span> is being run as (on Unix, default
 692               user id is <span class="QUOTE">"privoxy"</span>).</p>
 693             </dd>
 694           </dl>
 695         </div>
 696       </div>
 697
 698       <div class="SECT3">
 699         <h4 class="SECT3"><a name="TRUSTFILE" id="TRUSTFILE">7.2.7.
 700         trustfile</a></h4>
 701
 702         <div class="VARIABLELIST">
 703           <dl>
 704             <dt>Specifies:</dt>
 705
 706             <dd>
 707               <p>The name of the trust file to use</p>
 708             </dd>
 709
 710             <dt>Type of value:</dt>
 711
 712             <dd>
 713               <p>File name, relative to <tt class="LITERAL">confdir</tt></p>
 714             </dd>
 715
 716             <dt>Default value:</dt>
 717
 718             <dd>
 719               <p><span class="emphasis"><i class="EMPHASIS">Unset (commented
 720               out)</i></span>. When activated: trust (Unix) <span class=
 721               "emphasis"><i class="EMPHASIS">or</i></span> trust.txt
 722               (Windows)</p>
 723             </dd>
 724
 725             <dt>Effect if unset:</dt>
 726
 727             <dd>
 728               <p>The entire trust mechanism is disabled.</p>
 729             </dd>
 730
 731             <dt>Notes:</dt>
 732
 733             <dd>
 734               <p>The trust mechanism is an experimental feature for building
 735               white-lists and should be used with care. It is <span class=
 736               "emphasis"><i class="EMPHASIS">NOT</i></span> recommended for
 737               the casual user.</p>
 738
 739               <p>If you specify a trust file, <span class=
 740               "APPLICATION">Privoxy</span> will only allow access to sites
 741               that are specified in the trustfile. Sites can be listed in one
 742               of two ways:</p>
 743
 744               <p>Prepending a <tt class="LITERAL">~</tt> character limits
 745               access to this site only (and any sub-paths within this site),
 746               e.g. <tt class="LITERAL">~www.example.com</tt> allows access to
 747               <tt class="LITERAL">~www.example.com/features/news.html</tt>,
 748               etc.</p>
 749
 750               <p>Or, you can designate sites as <span class=
 751               "emphasis"><i class="EMPHASIS">trusted referrers</i></span>, by
 752               prepending the name with a <tt class="LITERAL">+</tt>
 753               character. The effect is that access to untrusted sites will be
 754               granted -- but only if a link from this trusted referrer was
 755               used to get there. The link target will then be added to the
 756               <span class="QUOTE">"trustfile"</span> so that future, direct
 757               accesses will be granted. Sites added via this mechanism do not
 758               become trusted referrers themselves (i.e. they are added with a
 759               <tt class="LITERAL">~</tt> designation). There is a limit of
 760               512 such entries, after which new entries will not be made.</p>
 761
 762               <p>If you use the <tt class="LITERAL">+</tt> operator in the
 763               trust file, it may grow considerably over time.</p>
 764
 765               <p>It is recommended that <span class=
 766               "APPLICATION">Privoxy</span> be compiled with the <tt class=
 767               "LITERAL">--disable-force</tt>, <tt class=
 768               "LITERAL">--disable-toggle</tt> and <tt class=
 769               "LITERAL">--disable-editor</tt> options, if this feature is to
 770               be used.</p>
 771
 772               <p>Possible applications include limiting Internet access for
 773               children.</p>
 774             </dd>
 775           </dl>
 776         </div>
 777       </div>
 778     </div>
 779
 780     <div class="SECT2">
 781       <h2 class="SECT2"><a name="DEBUGGING" id="DEBUGGING">7.3.
 782       Debugging</a></h2>
 783
 784       <p>These options are mainly useful when tracing a problem. Note that
 785       you might also want to invoke <span class="APPLICATION">Privoxy</span>
 786       with the <tt class="LITERAL">--no-daemon</tt> command line option when
 787       debugging.</p>
 788
 789       <div class="SECT3">
 790         <h4 class="SECT3"><a name="DEBUG" id="DEBUG">7.3.1. debug</a></h4>
 791
 792         <div class="VARIABLELIST">
 793           <dl>
 794             <dt>Specifies:</dt>
 795
 796             <dd>
 797               <p>Key values that determine what information gets logged.</p>
 798             </dd>
 799
 800             <dt>Type of value:</dt>
 801
 802             <dd>
 803               <p>Integer values</p>
 804             </dd>
 805
 806             <dt>Default value:</dt>
 807
 808             <dd>
 809               <p>0 (i.e.: only fatal errors (that cause Privoxy to exit) are
 810               logged)</p>
 811             </dd>
 812
 813             <dt>Effect if unset:</dt>
 814
 815             <dd>
 816               <p>Default value is used (see above).</p>
 817             </dd>
 818
 819             <dt>Notes:</dt>
 820
 821             <dd>
 822               <p>The available debug levels are:</p>
 823
 824               <table border="0" bgcolor="#E0E0E0" width="90%">
 825                 <tr>
 826                   <td>
 827                     <pre class="PROGRAMLISTING">
 828   debug     1 # Log the destination for each request <span class=
 829 "APPLICATION">Privoxy</span> let through. See also debug 1024.
 830   debug     2 # show each connection status
 831   debug     4 # show I/O status
 832   debug     8 # show header parsing
 833   debug    16 # log all data written to the network
 834   debug    32 # debug force feature
 835   debug    64 # debug regular expression filters
 836   debug   128 # debug redirects
 837   debug   256 # debug GIF de-animation
 838   debug   512 # Common Log Format
 839   debug  1024 # Log the destination for requests <span class=
 840 "APPLICATION">Privoxy</span> didn't let through, and the reason why.
 841   debug  2048 # CGI user interface
 842   debug  4096 # Startup banner and warnings.
 843   debug  8192 # Non-fatal errors
 844   debug 32768 # log all data read from the network
 845   debug 65536 # Log the applying actions
 846 </pre>
 847                   </td>
 848                 </tr>
 849               </table>
 850
 851               <p>To select multiple debug levels, you can either add them or
 852               use multiple <tt class="LITERAL">debug</tt> lines.</p>
 853
 854               <p>A debug level of 1 is informative because it will show you
 855               each request as it happens. <span class="emphasis"><i class=
 856               "EMPHASIS">1, 1024, 4096 and 8192 are recommended</i></span> so
 857               that you will notice when things go wrong. The other levels are
 858               probably only of interest if you are hunting down a specific
 859               problem. They can produce a hell of an output (especially
 860               16).</p>
 861
 862               <p><span class="APPLICATION">Privoxy</span> used to ship with
 863               the debug levels recommended above enabled by default, but due
 864               to privacy concerns 3.0.7 and later are configured to only log
 865               fatal errors.</p>
 866
 867               <p>If you are used to the more verbose settings, simply enable
 868               the debug lines below again.</p>
 869
 870               <p>If you want to use pure CLF (Common Log Format), you should
 871               set <span class="QUOTE">"debug 512"</span> <span class=
 872               "emphasis"><i class="EMPHASIS">ONLY</i></span> and not enable
 873               anything else.</p>
 874
 875               <p><span class="APPLICATION">Privoxy</span> has a hard-coded
 876               limit for the length of log messages. If it's reached, messages
 877               are logged truncated and marked with <span class="QUOTE">"...
 878               [too long, truncated]"</span>.</p>
 879
 880               <p>Please don't file any support requests without trying to
 881               reproduce the problem with increased debug level first. Once
 882               you read the log messages, you may even be able to solve the
 883               problem on your own.</p>
 884             </dd>
 885           </dl>
 886         </div>
 887       </div>
 888
 889       <div class="SECT3">
 890         <h4 class="SECT3"><a name="SINGLE-THREADED" id=
 891         "SINGLE-THREADED">7.3.2. single-threaded</a></h4>
 892
 893         <div class="VARIABLELIST">
 894           <dl>
 895             <dt>Specifies:</dt>
 896
 897             <dd>
 898               <p>Whether to run only one server thread.</p>
 899             </dd>
 900
 901             <dt>Type of value:</dt>
 902
 903             <dd>
 904               <p><span class="emphasis"><i class=
 905               "EMPHASIS">None</i></span></p>
 906             </dd>
 907
 908             <dt>Default value:</dt>
 909
 910             <dd>
 911               <p><span class="emphasis"><i class=
 912               "EMPHASIS">Unset</i></span></p>
 913             </dd>
 914
 915             <dt>Effect if unset:</dt>
 916
 917             <dd>
 918               <p>Multi-threaded (or, where unavailable: forked) operation,
 919               i.e. the ability to serve multiple requests simultaneously.</p>
 920             </dd>
 921
 922             <dt>Notes:</dt>
 923
 924             <dd>
 925               <p>This option is only there for debugging purposes.
 926               <span class="emphasis"><i class="EMPHASIS">It will drastically
 927               reduce performance.</i></span></p>
 928             </dd>
 929           </dl>
 930         </div>
 931       </div>
 932
 933       <div class="SECT3">
 934         <h4 class="SECT3"><a name="HOSTNAME" id="HOSTNAME">7.3.3.
 935         hostname</a></h4>
 936
 937         <div class="VARIABLELIST">
 938           <dl>
 939             <dt>Specifies:</dt>
 940
 941             <dd>
 942               <p>The hostname shown on the CGI pages.</p>
 943             </dd>
 944
 945             <dt>Type of value:</dt>
 946
 947             <dd>
 948               <p>Text</p>
 949             </dd>
 950
 951             <dt>Default value:</dt>
 952
 953             <dd>
 954               <p><span class="emphasis"><i class=
 955               "EMPHASIS">Unset</i></span></p>
 956             </dd>
 957
 958             <dt>Effect if unset:</dt>
 959
 960             <dd>
 961               <p>The hostname provided by the operating system is used.</p>
 962             </dd>
 963
 964             <dt>Notes:</dt>
 965
 966             <dd>
 967               <p>On some misconfigured systems resolving the hostname fails
 968               or takes too much time and slows Privoxy down. Setting a fixed
 969               hostname works around the problem.</p>
 970
 971               <p>In other circumstances it might be desirable to show a
 972               hostname other than the one returned by the operating system.
 973               For example if the system has several different hostnames and
 974               you don't want to use the first one.</p>
 975
 976               <p>Note that Privoxy does not validate the specified hostname
 977               value.</p>
 978             </dd>
 979           </dl>
 980         </div>
 981       </div>
 982     </div>
 983
 984     <div class="SECT2">
 985       <h2 class="SECT2"><a name="ACCESS-CONTROL" id="ACCESS-CONTROL">7.4.
 986       Access Control and Security</a></h2>
 987
 988       <p>This section of the config file controls the security-relevant
 989       aspects of <span class="APPLICATION">Privoxy</span>'s
 990       configuration.</p>
 991
 992       <div class="SECT3">
 993         <h4 class="SECT3"><a name="LISTEN-ADDRESS" id="LISTEN-ADDRESS">7.4.1.
 994         listen-address</a></h4>
 995
 996         <div class="VARIABLELIST">
 997           <dl>
 998             <dt>Specifies:</dt>
 999
1000             <dd>
1001               <p>The address and TCP port on which <span class=
1002               "APPLICATION">Privoxy</span> will listen for client
1003               requests.</p>
1004             </dd>
1005
1006             <dt>Type of value:</dt>
1007
1008             <dd>
1009               <p>[<tt class="REPLACEABLE"><i>IP-Address</i></tt>]:<tt class=
1010               "REPLACEABLE"><i>Port</i></tt></p>
1011
1012               <p>[<tt class="REPLACEABLE"><i>Hostname</i></tt>]:<tt class=
1013               "REPLACEABLE"><i>Port</i></tt></p>
1014             </dd>
1015
1016             <dt>Default value:</dt>
1017
1018             <dd>
1019               <p>127.0.0.1:8118</p>
1020             </dd>
1021
1022             <dt>Effect if unset:</dt>
1023
1024             <dd>
1025               <p>Bind to 127.0.0.1 (IPv4 localhost), port 8118. This is
1026               suitable and recommended for home users who run <span class=
1027               "APPLICATION">Privoxy</span> on the same machine as their
1028               browser.</p>
1029             </dd>
1030
1031             <dt>Notes:</dt>
1032
1033             <dd>
1034               <p>You will need to configure your browser(s) to this proxy
1035               address and port.</p>
1036
1037               <p>If you already have another service running on port 8118, or
1038               if you want to serve requests from other machines (e.g. on your
1039               local network) as well, you will need to override the
1040               default.</p>
1041
1042               <p>You can use this statement multiple times to make
1043               <span class="APPLICATION">Privoxy</span> listen on more ports
1044               or more <abbr class="ABBREV">IP</abbr> addresses. Suitable if
1045               your operating system does not support sharing <abbr class=
1046               "ABBREV">IPv6</abbr> and <abbr class="ABBREV">IPv4</abbr>
1047               protocols on the same socket.</p>
1048
1049               <p>If a hostname is used instead of an IP address, <span class=
1050               "APPLICATION">Privoxy</span> will try to resolve it to an IP
1051               address and if there are multiple, use the first one
1052               returned.</p>
1053
1054               <p>If the address for the hostname isn't already known on the
1055               system (for example because it's in /etc/hostname), this may
1056               result in DNS traffic.</p>
1057
1058               <p>If the specified address isn't available on the system, or
1059               if the hostname can't be resolved, <span class=
1060               "APPLICATION">Privoxy</span> will fail to start.</p>
1061
1062               <p>IPv6 addresses containing colons have to be quoted by
1063               brackets. They can only be used if <span class=
1064               "APPLICATION">Privoxy</span> has been compiled with IPv6
1065               support. If you aren't sure if your version supports it, have a
1066               look at <tt class=
1067               "LITERAL">http://config.privoxy.org/show-status</tt>.</p>
1068
1069               <p>Some operating systems will prefer IPv6 to IPv4 addresses
1070               even if the system has no IPv6 connectivity which is usually
1071               not expected by the user. Some even rely on DNS to resolve
1072               localhost which mean the "localhost" address used may not
1073               actually be local.</p>
1074
1075               <p>It is therefore recommended to explicitly configure the
1076               intended IP address instead of relying on the operating system,
1077               unless there's a strong reason not to.</p>
1078
1079               <p>If you leave out the address, <span class=
1080               "APPLICATION">Privoxy</span> will bind to all IPv4 interfaces
1081               (addresses) on your machine and may become reachable from the
1082               Internet and/or the local network. Be aware that some GNU/Linux
1083               distributions modify that behaviour without updating the
1084               documentation. Check for non-standard patches if your
1085               <span class="APPLICATION">Privoxy</span> version behaves
1086               differently.</p>
1087
1088               <p>If you configure <span class="APPLICATION">Privoxy</span> to
1089               be reachable from the network, consider using <a href=
1090               "config.html#ACLS">access control lists</a> (ACL's, see below),
1091               and/or a firewall.</p>
1092
1093               <p>If you open <span class="APPLICATION">Privoxy</span> to
1094               untrusted users, you will also want to make sure that the
1095               following actions are disabled: <tt class="LITERAL"><a href=
1096               "config.html#ENABLE-EDIT-ACTIONS">enable-edit-actions</a></tt>
1097               and <tt class="LITERAL"><a href=
1098               "config.html#ENABLE-REMOTE-TOGGLE">enable-remote-toggle</a></tt></p>
1099             </dd>
1100
1101             <dt>Example:</dt>
1102
1103             <dd>
1104               <p>Suppose you are running <span class=
1105               "APPLICATION">Privoxy</span> on a machine which has the address
1106               192.168.0.1 on your local private network (192.168.0.0) and has
1107               another outside connection with a different address. You want
1108               it to serve requests from inside only:</p>
1109
1110               <table border="0" bgcolor="#E0E0E0" width="90%">
1111                 <tr>
1112                   <td>
1113                     <pre class="PROGRAMLISTING">
1114   listen-address  192.168.0.1:8118
1115 </pre>
1116                   </td>
1117                 </tr>
1118               </table>
1119
1120               <p>Suppose you are running <span class=
1121               "APPLICATION">Privoxy</span> on an IPv6-capable machine and you
1122               want it to listen on the IPv6 address of the loopback
1123               device:</p>
1124
1125               <table border="0" bgcolor="#E0E0E0" width="90%">
1126                 <tr>
1127                   <td>
1128                     <pre class="PROGRAMLISTING">
1129   listen-address [::1]:8118
1130 </pre>
1131                   </td>
1132                 </tr>
1133               </table>
1134             </dd>
1135           </dl>
1136         </div>
1137       </div>
1138
1139       <div class="SECT3">
1140         <h4 class="SECT3"><a name="TOGGLE" id="TOGGLE">7.4.2. toggle</a></h4>
1141
1142         <div class="VARIABLELIST">
1143           <dl>
1144             <dt>Specifies:</dt>
1145
1146             <dd>
1147               <p>Initial state of "toggle" status</p>
1148             </dd>
1149
1150             <dt>Type of value:</dt>
1151
1152             <dd>
1153               <p>1 or 0</p>
1154             </dd>
1155
1156             <dt>Default value:</dt>
1157
1158             <dd>
1159               <p>1</p>
1160             </dd>
1161
1162             <dt>Effect if unset:</dt>
1163
1164             <dd>
1165               <p>Act as if toggled on</p>
1166             </dd>
1167
1168             <dt>Notes:</dt>
1169
1170             <dd>
1171               <p>If set to 0, <span class="APPLICATION">Privoxy</span> will
1172               start in <span class="QUOTE">"toggled off"</span> mode, i.e.
1173               mostly behave like a normal, content-neutral proxy with both ad
1174               blocking and content filtering disabled. See <tt class=
1175               "LITERAL">enable-remote-toggle</tt> below.</p>
1176             </dd>
1177           </dl>
1178         </div>
1179       </div>
1180
1181       <div class="SECT3">
1182         <h4 class="SECT3"><a name="ENABLE-REMOTE-TOGGLE" id=
1183         "ENABLE-REMOTE-TOGGLE">7.4.3. enable-remote-toggle</a></h4>
1184
1185         <div class="VARIABLELIST">
1186           <dl>
1187             <dt>Specifies:</dt>
1188
1189             <dd>
1190               <p>Whether or not the <a href=
1191               "http://config.privoxy.org/toggle" target="_top">web-based
1192               toggle feature</a> may be used</p>
1193             </dd>
1194
1195             <dt>Type of value:</dt>
1196
1197             <dd>
1198               <p>0 or 1</p>
1199             </dd>
1200
1201             <dt>Default value:</dt>
1202
1203             <dd>
1204               <p>0</p>
1205             </dd>
1206
1207             <dt>Effect if unset:</dt>
1208
1209             <dd>
1210               <p>The web-based toggle feature is disabled.</p>
1211             </dd>
1212
1213             <dt>Notes:</dt>
1214
1215             <dd>
1216               <p>When toggled off, <span class="APPLICATION">Privoxy</span>
1217               mostly acts like a normal, content-neutral proxy, i.e. doesn't
1218               block ads or filter content.</p>
1219
1220               <p>Access to the toggle feature can <span class=
1221               "emphasis"><i class="EMPHASIS">not</i></span> be controlled
1222               separately by <span class="QUOTE">"ACLs"</span> or HTTP
1223               authentication, so that everybody who can access <span class=
1224               "APPLICATION">Privoxy</span> (see <span class=
1225               "QUOTE">"ACLs"</span> and <tt class=
1226               "LITERAL">listen-address</tt> above) can toggle it for all
1227               users. So this option is <span class="emphasis"><i class=
1228               "EMPHASIS">not recommended</i></span> for multi-user
1229               environments with untrusted users.</p>
1230
1231               <p>Note that malicious client side code (e.g Java) is also
1232               capable of using this option.</p>
1233
1234               <p>As a lot of <span class="APPLICATION">Privoxy</span> users
1235               don't read documentation, this feature is disabled by
1236               default.</p>
1237
1238               <p>Note that you must have compiled <span class=
1239               "APPLICATION">Privoxy</span> with support for this feature,
1240               otherwise this option has no effect.</p>
1241             </dd>
1242           </dl>
1243         </div>
1244       </div>
1245
1246       <div class="SECT3">
1247         <h4 class="SECT3"><a name="ENABLE-REMOTE-HTTP-TOGGLE" id=
1248         "ENABLE-REMOTE-HTTP-TOGGLE">7.4.4. enable-remote-http-toggle</a></h4>
1249
1250         <div class="VARIABLELIST">
1251           <dl>
1252             <dt>Specifies:</dt>
1253
1254             <dd>
1255               <p>Whether or not Privoxy recognizes special HTTP headers to
1256               change its behaviour.</p>
1257             </dd>
1258
1259             <dt>Type of value:</dt>
1260
1261             <dd>
1262               <p>0 or 1</p>
1263             </dd>
1264
1265             <dt>Default value:</dt>
1266
1267             <dd>
1268               <p>0</p>
1269             </dd>
1270
1271             <dt>Effect if unset:</dt>
1272
1273             <dd>
1274               <p>Privoxy ignores special HTTP headers.</p>
1275             </dd>
1276
1277             <dt>Notes:</dt>
1278
1279             <dd>
1280               <p>When toggled on, the client can change <span class=
1281               "APPLICATION">Privoxy's</span> behaviour by setting special
1282               HTTP headers. Currently the only supported special header is
1283               <span class="QUOTE">"X-Filter: No"</span>, to disable filtering
1284               for the ongoing request, even if it is enabled in one of the
1285               action files.</p>
1286
1287               <p>This feature is disabled by default. If you are using
1288               <span class="APPLICATION">Privoxy</span> in a environment with
1289               trusted clients, you may enable this feature at your
1290               discretion. Note that malicious client side code (e.g Java) is
1291               also capable of using this feature.</p>
1292
1293               <p>This option will be removed in future releases as it has
1294               been obsoleted by the more general header taggers.</p>
1295             </dd>
1296           </dl>
1297         </div>
1298       </div>
1299
1300       <div class="SECT3">
1301         <h4 class="SECT3"><a name="ENABLE-EDIT-ACTIONS" id=
1302         "ENABLE-EDIT-ACTIONS">7.4.5. enable-edit-actions</a></h4>
1303
1304         <div class="VARIABLELIST">
1305           <dl>
1306             <dt>Specifies:</dt>
1307
1308             <dd>
1309               <p>Whether or not the <a href=
1310               "http://config.privoxy.org/show-status" target="_top">web-based
1311               actions file editor</a> may be used</p>
1312             </dd>
1313
1314             <dt>Type of value:</dt>
1315
1316             <dd>
1317               <p>0 or 1</p>
1318             </dd>
1319
1320             <dt>Default value:</dt>
1321
1322             <dd>
1323               <p>0</p>
1324             </dd>
1325
1326             <dt>Effect if unset:</dt>
1327
1328             <dd>
1329               <p>The web-based actions file editor is disabled.</p>
1330             </dd>
1331
1332             <dt>Notes:</dt>
1333
1334             <dd>
1335               <p>Access to the editor can <span class="emphasis"><i class=
1336               "EMPHASIS">not</i></span> be controlled separately by
1337               <span class="QUOTE">"ACLs"</span> or HTTP authentication, so
1338               that everybody who can access <span class=
1339               "APPLICATION">Privoxy</span> (see <span class=
1340               "QUOTE">"ACLs"</span> and <tt class=
1341               "LITERAL">listen-address</tt> above) can modify its
1342               configuration for all users.</p>
1343
1344               <p>This option is <span class="emphasis"><i class=
1345               "EMPHASIS">not recommended</i></span> for environments with
1346               untrusted users and as a lot of <span class=
1347               "APPLICATION">Privoxy</span> users don't read documentation,
1348               this feature is disabled by default.</p>
1349
1350               <p>Note that malicious client side code (e.g Java) is also
1351               capable of using the actions editor and you shouldn't enable
1352               this options unless you understand the consequences and are
1353               sure your browser is configured correctly.</p>
1354
1355               <p>Note that you must have compiled <span class=
1356               "APPLICATION">Privoxy</span> with support for this feature,
1357               otherwise this option has no effect.</p>
1358             </dd>
1359           </dl>
1360         </div>
1361       </div>
1362
1363       <div class="SECT3">
1364         <h4 class="SECT3"><a name="ENFORCE-BLOCKS" id="ENFORCE-BLOCKS">7.4.6.
1365         enforce-blocks</a></h4>
1366
1367         <div class="VARIABLELIST">
1368           <dl>
1369             <dt>Specifies:</dt>
1370
1371             <dd>
1372               <p>Whether the user is allowed to ignore blocks and can
1373               <span class="QUOTE">"go there anyway"</span>.</p>
1374             </dd>
1375
1376             <dt>Type of value:</dt>
1377
1378             <dd>
1379               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
1380             </dd>
1381
1382             <dt>Default value:</dt>
1383
1384             <dd>
1385               <p><span class="emphasis"><i class="EMPHASIS">0</i></span></p>
1386             </dd>
1387
1388             <dt>Effect if unset:</dt>
1389
1390             <dd>
1391               <p>Blocks are not enforced.</p>
1392             </dd>
1393
1394             <dt>Notes:</dt>
1395
1396             <dd>
1397               <p><span class="APPLICATION">Privoxy</span> is mainly used to
1398               block and filter requests as a service to the user, for example
1399               to block ads and other junk that clogs the pipes. <span class=
1400               "APPLICATION">Privoxy's</span> configuration isn't perfect and
1401               sometimes innocent pages are blocked. In this situation it
1402               makes sense to allow the user to enforce the request and have
1403               <span class="APPLICATION">Privoxy</span> ignore the block.</p>
1404
1405               <p>In the default configuration <span class=
1406               "APPLICATION">Privoxy's</span> <span class=
1407               "QUOTE">"Blocked"</span> page contains a <span class=
1408               "QUOTE">"go there anyway"</span> link to adds a special string
1409               (the force prefix) to the request URL. If that link is used,
1410               <span class="APPLICATION">Privoxy</span> will detect the force
1411               prefix, remove it again and let the request pass.</p>
1412
1413               <p>Of course <span class="APPLICATION">Privoxy</span> can also
1414               be used to enforce a network policy. In that case the user
1415               obviously should not be able to bypass any blocks, and that's
1416               what the <span class="QUOTE">"enforce-blocks"</span> option is
1417               for. If it's enabled, <span class="APPLICATION">Privoxy</span>
1418               hides the <span class="QUOTE">"go there anyway"</span> link. If
1419               the user adds the force prefix by hand, it will not be accepted
1420               and the circumvention attempt is logged.</p>
1421             </dd>
1422
1423             <dt>Examples:</dt>
1424
1425             <dd>
1426               <p>enforce-blocks 1</p>
1427             </dd>
1428           </dl>
1429         </div>
1430       </div>
1431
1432       <div class="SECT3">
1433         <h4 class="SECT3"><a name="ACLS" id="ACLS">7.4.7. ACLs: permit-access
1434         and deny-access</a></h4><a name="PERMIT-ACCESS" id=
1435         "PERMIT-ACCESS"></a><a name="DENY-ACCESS" id="DENY-ACCESS"></a>
1436
1437         <div class="VARIABLELIST">
1438           <dl>
1439             <dt>Specifies:</dt>
1440
1441             <dd>
1442               <p>Who can access what.</p>
1443             </dd>
1444
1445             <dt>Type of value:</dt>
1446
1447             <dd>
1448               <p><tt class="REPLACEABLE"><i>src_addr</i></tt>[:<tt class=
1449               "REPLACEABLE"><i>port</i></tt>][/<tt class=
1450               "REPLACEABLE"><i>src_masklen</i></tt>] [<tt class=
1451               "REPLACEABLE"><i>dst_addr</i></tt>[:<tt class=
1452               "REPLACEABLE"><i>port</i></tt>][/<tt class=
1453               "REPLACEABLE"><i>dst_masklen</i></tt>]]</p>
1454
1455               <p>Where <tt class="REPLACEABLE"><i>src_addr</i></tt> and
1456               <tt class="REPLACEABLE"><i>dst_addr</i></tt> are IPv4 addresses
1457               in dotted decimal notation or valid DNS names, <tt class=
1458               "REPLACEABLE"><i>port</i></tt> is a port number, and <tt class=
1459               "REPLACEABLE"><i>src_masklen</i></tt> and <tt class=
1460               "REPLACEABLE"><i>dst_masklen</i></tt> are subnet masks in CIDR
1461               notation, i.e. integer values from 2 to 30 representing the
1462               length (in bits) of the network address. The masks and the
1463               whole destination part are optional.</p>
1464
1465               <p>If your system implements <a href=
1466               "http://tools.ietf.org/html/rfc3493" target="_top">RFC
1467               3493</a>, then <tt class="REPLACEABLE"><i>src_addr</i></tt> and
1468               <tt class="REPLACEABLE"><i>dst_addr</i></tt> can be IPv6
1469               addresses delimeted by brackets, <tt class=
1470               "REPLACEABLE"><i>port</i></tt> can be a number or a service
1471               name, and <tt class="REPLACEABLE"><i>src_masklen</i></tt> and
1472               <tt class="REPLACEABLE"><i>dst_masklen</i></tt> can be a number
1473               from 0 to 128.</p>
1474             </dd>
1475
1476             <dt>Default value:</dt>
1477
1478             <dd>
1479               <p><span class="emphasis"><i class=
1480               "EMPHASIS">Unset</i></span></p>
1481
1482               <p>If no <tt class="REPLACEABLE"><i>port</i></tt> is specified,
1483               any port will match. If no <tt class=
1484               "REPLACEABLE"><i>src_masklen</i></tt> or <tt class=
1485               "REPLACEABLE"><i>src_masklen</i></tt> is given, the complete IP
1486               address has to match (i.e. 32 bits for IPv4 and 128 bits for
1487               IPv6).</p>
1488             </dd>
1489
1490             <dt>Effect if unset:</dt>
1491
1492             <dd>
1493               <p>Don't restrict access further than implied by <tt class=
1494               "LITERAL">listen-address</tt></p>
1495             </dd>
1496
1497             <dt>Notes:</dt>
1498
1499             <dd>
1500               <p>Access controls are included at the request of ISPs and
1501               systems administrators, and <span class="emphasis"><i class=
1502               "EMPHASIS">are not usually needed by individual
1503               users</i></span>. For a typical home user, it will normally
1504               suffice to ensure that <span class="APPLICATION">Privoxy</span>
1505               only listens on the localhost (127.0.0.1) or internal (home)
1506               network address by means of the <a href=
1507               "config.html#LISTEN-ADDRESS"><span class="emphasis"><i class=
1508               "EMPHASIS">listen-address</i></span></a> option.</p>
1509
1510               <p>Please see the warnings in the FAQ that <span class=
1511               "APPLICATION">Privoxy</span> is not intended to be a substitute
1512               for a firewall or to encourage anyone to defer addressing basic
1513               security weaknesses.</p>
1514
1515               <p>Multiple ACL lines are OK. If any ACLs are specified,
1516               <span class="APPLICATION">Privoxy</span> only talks to IP
1517               addresses that match at least one <tt class=
1518               "LITERAL">permit-access</tt> line and don't match any
1519               subsequent <tt class="LITERAL">deny-access</tt> line. In other
1520               words, the last match wins, with the default being <tt class=
1521               "LITERAL">deny-access</tt>.</p>
1522
1523               <p>If <span class="APPLICATION">Privoxy</span> is using a
1524               forwarder (see <tt class="LITERAL">forward</tt> below) for a
1525               particular destination URL, the <tt class=
1526               "REPLACEABLE"><i>dst_addr</i></tt> that is examined is the
1527               address of the forwarder and <span class="emphasis"><i class=
1528               "EMPHASIS">NOT</i></span> the address of the ultimate target.
1529               This is necessary because it may be impossible for the local
1530               <span class="APPLICATION">Privoxy</span> to determine the IP
1531               address of the ultimate target (that's often what gateways are
1532               used for).</p>
1533
1534               <p>You should prefer using IP addresses over DNS names, because
1535               the address lookups take time. All DNS names must resolve! You
1536               can <span class="emphasis"><i class="EMPHASIS">not</i></span>
1537               use domain patterns like <span class="QUOTE">"*.org"</span> or
1538               partial domain names. If a DNS name resolves to multiple IP
1539               addresses, only the first one is used.</p>
1540
1541               <p>Some systems allow IPv4 clients to connect to IPv6 server
1542               sockets. Then the client's IPv4 address will be translated by
1543               the system into IPv6 address space with special prefix
1544               ::ffff:0:0/96 (so called IPv4 mapped IPv6 address).
1545               <span class="APPLICATION">Privoxy</span> can handle it and maps
1546               such ACL addresses automatically.</p>
1547
1548               <p>Denying access to particular sites by ACL may have undesired
1549               side effects if the site in question is hosted on a machine
1550               which also hosts other sites (most sites are).</p>
1551             </dd>
1552
1553             <dt>Examples:</dt>
1554
1555             <dd>
1556               <p>Explicitly define the default behavior if no ACL and
1557               <tt class="LITERAL">listen-address</tt> are set: <span class=
1558               "QUOTE">"localhost"</span> is OK. The absence of a <tt class=
1559               "REPLACEABLE"><i>dst_addr</i></tt> implies that <span class=
1560               "emphasis"><i class="EMPHASIS">all</i></span> destination
1561               addresses are OK:</p>
1562
1563               <table border="0" bgcolor="#E0E0E0" width="90%">
1564                 <tr>
1565                   <td>
1566                     <pre class="SCREEN">
1567   permit-access  localhost
1568 </pre>
1569                   </td>
1570                 </tr>
1571               </table>
1572
1573               <p>Allow any host on the same class C subnet as www.privoxy.org
1574               access to nothing but www.example.com (or other domains hosted
1575               on the same system):</p>
1576
1577               <table border="0" bgcolor="#E0E0E0" width="90%">
1578                 <tr>
1579                   <td>
1580                     <pre class="SCREEN">
1581   permit-access  www.privoxy.org/24 www.example.com/32
1582 </pre>
1583                   </td>
1584                 </tr>
1585               </table>
1586
1587               <p>Allow access from any host on the 26-bit subnet
1588               192.168.45.64 to anywhere, with the exception that
1589               192.168.45.73 may not access the IP address behind
1590               www.dirty-stuff.example.com:</p>
1591
1592               <table border="0" bgcolor="#E0E0E0" width="90%">
1593                 <tr>
1594                   <td>
1595                     <pre class="SCREEN">
1596   permit-access  192.168.45.64/26
1597   deny-access    192.168.45.73    www.dirty-stuff.example.com
1598 </pre>
1599                   </td>
1600                 </tr>
1601               </table>
1602
1603               <p>Allow access from the IPv4 network 192.0.2.0/24 even if
1604               listening on an IPv6 wild card address (not supported on all
1605               platforms):</p>
1606
1607               <table border="0" bgcolor="#E0E0E0" width="90%">
1608                 <tr>
1609                   <td>
1610                     <pre class="PROGRAMLISTING">
1611   permit-access  192.0.2.0/24
1612 </pre>
1613                   </td>
1614                 </tr>
1615               </table>
1616
1617               <p>This is equivalent to the following line even if listening
1618               on an IPv4 address (not supported on all platforms):</p>
1619
1620               <table border="0" bgcolor="#E0E0E0" width="90%">
1621                 <tr>
1622                   <td>
1623                     <pre class="PROGRAMLISTING">
1624   permit-access  [::ffff:192.0.2.0]/120
1625 </pre>
1626                   </td>
1627                 </tr>
1628               </table>
1629             </dd>
1630           </dl>
1631         </div>
1632       </div>
1633
1634       <div class="SECT3">
1635         <h4 class="SECT3"><a name="BUFFER-LIMIT" id="BUFFER-LIMIT">7.4.8.
1636         buffer-limit</a></h4>
1637
1638         <div class="VARIABLELIST">
1639           <dl>
1640             <dt>Specifies:</dt>
1641
1642             <dd>
1643               <p>Maximum size of the buffer for content filtering.</p>
1644             </dd>
1645
1646             <dt>Type of value:</dt>
1647
1648             <dd>
1649               <p>Size in Kbytes</p>
1650             </dd>
1651
1652             <dt>Default value:</dt>
1653
1654             <dd>
1655               <p>4096</p>
1656             </dd>
1657
1658             <dt>Effect if unset:</dt>
1659
1660             <dd>
1661               <p>Use a 4MB (4096 KB) limit.</p>
1662             </dd>
1663
1664             <dt>Notes:</dt>
1665
1666             <dd>
1667               <p>For content filtering, i.e. the <tt class=
1668               "LITERAL">+filter</tt> and <tt class=
1669               "LITERAL">+deanimate-gif</tt> actions, it is necessary that
1670               <span class="APPLICATION">Privoxy</span> buffers the entire
1671               document body. This can be potentially dangerous, since a
1672               server could just keep sending data indefinitely and wait for
1673               your RAM to exhaust -- with nasty consequences. Hence this
1674               option.</p>
1675
1676               <p>When a document buffer size reaches the <tt class=
1677               "LITERAL">buffer-limit</tt>, it is flushed to the client
1678               unfiltered and no further attempt to filter the rest of the
1679               document is made. Remember that there may be multiple threads
1680               running, which might require up to <tt class=
1681               "LITERAL">buffer-limit</tt> Kbytes <span class=
1682               "emphasis"><i class="EMPHASIS">each</i></span>, unless you have
1683               enabled <span class="QUOTE">"single-threaded"</span> above.</p>
1684             </dd>
1685           </dl>
1686         </div>
1687       </div>
1688     </div>
1689
1690     <div class="SECT2">
1691       <h2 class="SECT2"><a name="FORWARDING" id="FORWARDING">7.5.
1692       Forwarding</a></h2>
1693
1694       <p>This feature allows routing of HTTP requests through a chain of
1695       multiple proxies.</p>
1696
1697       <p>Forwarding can be used to chain Privoxy with a caching proxy to
1698       speed up browsing. Using a parent proxy may also be necessary if the
1699       machine that <span class="APPLICATION">Privoxy</span> runs on has no
1700       direct Internet access.</p>
1701
1702       <p>Note that parent proxies can severely decrease your privacy level.
1703       For example a parent proxy could add your IP address to the request
1704       headers and if it's a caching proxy it may add the <span class=
1705       "QUOTE">"Etag"</span> header to revalidation requests again, even
1706       though you configured Privoxy to remove it. It may also ignore
1707       Privoxy's header time randomization and use the original values which
1708       could be used by the server as cookie replacement to track your steps
1709       between visits.</p>
1710
1711       <p>Also specified here are SOCKS proxies. <span class=
1712       "APPLICATION">Privoxy</span> supports the SOCKS 4 and SOCKS 4A
1713       protocols.</p>
1714
1715       <div class="SECT3">
1716         <h4 class="SECT3"><a name="FORWARD" id="FORWARD">7.5.1.
1717         forward</a></h4>
1718
1719         <div class="VARIABLELIST">
1720           <dl>
1721             <dt>Specifies:</dt>
1722
1723             <dd>
1724               <p>To which parent HTTP proxy specific requests should be
1725               routed.</p>
1726             </dd>
1727
1728             <dt>Type of value:</dt>
1729
1730             <dd>
1731               <p><tt class="REPLACEABLE"><i>target_pattern</i></tt>
1732               <tt class="REPLACEABLE"><i>http_parent</i></tt>[:<tt class=
1733               "REPLACEABLE"><i>port</i></tt>]</p>
1734
1735               <p>where <tt class="REPLACEABLE"><i>target_pattern</i></tt> is
1736               a <a href="actions-file.html#AF-PATTERNS">URL pattern</a> that
1737               specifies to which requests (i.e. URLs) this forward rule shall
1738               apply. Use <tt class="LITERAL">/</tt> to denote <span class=
1739               "QUOTE">"all URLs"</span>. <tt class=
1740               "REPLACEABLE"><i>http_parent</i></tt>[:<tt class=
1741               "REPLACEABLE"><i>port</i></tt>] is the DNS name or IP address
1742               of the parent HTTP proxy through which the requests should be
1743               forwarded, optionally followed by its listening port (default:
1744               8000). Use a single dot (<tt class="LITERAL">.</tt>) to denote
1745               <span class="QUOTE">"no forwarding"</span>.</p>
1746             </dd>
1747
1748             <dt>Default value:</dt>
1749
1750             <dd>
1751               <p><span class="emphasis"><i class=
1752               "EMPHASIS">Unset</i></span></p>
1753             </dd>
1754
1755             <dt>Effect if unset:</dt>
1756
1757             <dd>
1758               <p>Don't use parent HTTP proxies.</p>
1759             </dd>
1760
1761             <dt>Notes:</dt>
1762
1763             <dd>
1764               <p>If <tt class="REPLACEABLE"><i>http_parent</i></tt> is
1765               <span class="QUOTE">"."</span>, then requests are not forwarded
1766               to another HTTP proxy but are made directly to the web
1767               servers.</p>
1768
1769               <p><tt class="REPLACEABLE"><i>http_parent</i></tt> can be a
1770               numerical IPv6 address (if <a href=
1771               "http://tools.ietf.org/html/rfc3493" target="_top">RFC 3493</a>
1772               is implemented). To prevent clashes with the port delimiter,
1773               the whole IP address has to be put into brackets. On the other
1774               hand a <tt class="REPLACEABLE"><i>target_pattern</i></tt>
1775               containing an IPv6 address has to be put into angle brackets
1776               (normal brackets are reserved for regular expressions
1777               already).</p>
1778
1779               <p>Multiple lines are OK, they are checked in sequence, and the
1780               last match wins.</p>
1781             </dd>
1782
1783             <dt>Examples:</dt>
1784
1785             <dd>
1786               <p>Everything goes to an example parent proxy, except SSL on
1787               port 443 (which it doesn't handle):</p>
1788
1789               <table border="0" bgcolor="#E0E0E0" width="90%">
1790                 <tr>
1791                   <td>
1792                     <pre class="SCREEN">
1793   forward   /      parent-proxy.example.org:8080
1794   forward   :443   .
1795 </pre>
1796                   </td>
1797                 </tr>
1798               </table>
1799
1800               <p>Everything goes to our example ISP's caching proxy, except
1801               for requests to that ISP's sites:</p>
1802
1803               <table border="0" bgcolor="#E0E0E0" width="90%">
1804                 <tr>
1805                   <td>
1806                     <pre class="SCREEN">
1807   forward   /                  caching-proxy.isp.example.net:8000
1808   forward   .isp.example.net   .
1809 </pre>
1810                   </td>
1811                 </tr>
1812               </table>
1813
1814               <p>Parent proxy specified by an IPv6 address:</p>
1815
1816               <table border="0" bgcolor="#E0E0E0" width="90%">
1817                 <tr>
1818                   <td>
1819                     <pre class="PROGRAMLISTING">
1820   forward   /                   [2001:DB8::1]:8000
1821 </pre>
1822                   </td>
1823                 </tr>
1824               </table>
1825
1826               <p>Suppose your parent proxy doesn't support IPv6:</p>
1827
1828               <table border="0" bgcolor="#E0E0E0" width="90%">
1829                 <tr>
1830                   <td>
1831                     <pre class="PROGRAMLISTING">
1832   forward  /                        parent-proxy.example.org:8000
1833   forward  ipv6-server.example.org  .
1834   forward  &lt;[2-3][0-9a-f][0-9a-f][0-9a-f]:*&gt;   .
1835 </pre>
1836                   </td>
1837                 </tr>
1838               </table>
1839             </dd>
1840           </dl>
1841         </div>
1842       </div>
1843
1844       <div class="SECT3">
1845         <h4 class="SECT3"><a name="SOCKS" id="SOCKS">7.5.2. forward-socks4,
1846         forward-socks4a, forward-socks5 and forward-socks5t</a></h4><a name=
1847         "FORWARD-SOCKS4" id="FORWARD-SOCKS4"></a><a name="FORWARD-SOCKS4A"
1848         id="FORWARD-SOCKS4A"></a>
1849
1850         <div class="VARIABLELIST">
1851           <dl>
1852             <dt>Specifies:</dt>
1853
1854             <dd>
1855               <p>Through which SOCKS proxy (and optionally to which parent
1856               HTTP proxy) specific requests should be routed.</p>
1857             </dd>
1858
1859             <dt>Type of value:</dt>
1860
1861             <dd>
1862               <p><tt class="REPLACEABLE"><i>target_pattern</i></tt>
1863               <tt class="REPLACEABLE"><i>socks_proxy</i></tt>[:<tt class=
1864               "REPLACEABLE"><i>port</i></tt>] <tt class=
1865               "REPLACEABLE"><i>http_parent</i></tt>[:<tt class=
1866               "REPLACEABLE"><i>port</i></tt>]</p>
1867
1868               <p>where <tt class="REPLACEABLE"><i>target_pattern</i></tt> is
1869               a <a href="actions-file.html#AF-PATTERNS">URL pattern</a> that
1870               specifies to which requests (i.e. URLs) this forward rule shall
1871               apply. Use <tt class="LITERAL">/</tt> to denote <span class=
1872               "QUOTE">"all URLs"</span>. <tt class=
1873               "REPLACEABLE"><i>http_parent</i></tt> and <tt class=
1874               "REPLACEABLE"><i>socks_proxy</i></tt> are IP addresses in
1875               dotted decimal notation or valid DNS names (<tt class=
1876               "REPLACEABLE"><i>http_parent</i></tt> may be <span class=
1877               "QUOTE">"."</span> to denote <span class="QUOTE">"no HTTP
1878               forwarding"</span>), and the optional <tt class=
1879               "REPLACEABLE"><i>port</i></tt> parameters are TCP ports, i.e.
1880               integer values from 1 to 65535</p>
1881             </dd>
1882
1883             <dt>Default value:</dt>
1884
1885             <dd>
1886               <p><span class="emphasis"><i class=
1887               "EMPHASIS">Unset</i></span></p>
1888             </dd>
1889
1890             <dt>Effect if unset:</dt>
1891
1892             <dd>
1893               <p>Don't use SOCKS proxies.</p>
1894             </dd>
1895
1896             <dt>Notes:</dt>
1897
1898             <dd>
1899               <p>Multiple lines are OK, they are checked in sequence, and the
1900               last match wins.</p>
1901
1902               <p>The difference between <tt class=
1903               "LITERAL">forward-socks4</tt> and <tt class=
1904               "LITERAL">forward-socks4a</tt> is that in the SOCKS 4A
1905               protocol, the DNS resolution of the target hostname happens on
1906               the SOCKS server, while in SOCKS 4 it happens locally.</p>
1907
1908               <p>With <tt class="LITERAL">forward-socks5</tt> the DNS
1909               resolution will happen on the remote server as well.</p>
1910
1911               <p><tt class="LITERAL">forward-socks5t</tt> works like vanilla
1912               <tt class="LITERAL">forward-socks5</tt> but lets <span class=
1913               "APPLICATION">Privoxy</span> additionally use Tor-specific
1914               SOCKS extensions. Currently the only supported SOCKS extension
1915               is optimistic data which can reduce the latency for the first
1916               request made on a newly created connection.</p>
1917
1918               <p><tt class="REPLACEABLE"><i>socks_proxy</i></tt> and
1919               <tt class="REPLACEABLE"><i>http_parent</i></tt> can be a
1920               numerical IPv6 address (if <a href=
1921               "http://tools.ietf.org/html/rfc3493" target="_top">RFC 3493</a>
1922               is implemented). To prevent clashes with the port delimiter,
1923               the whole IP address has to be put into brackets. On the other
1924               hand a <tt class="REPLACEABLE"><i>target_pattern</i></tt>
1925               containing an IPv6 address has to be put into angle brackets
1926               (normal brackets are reserved for regular expressions
1927               already).</p>
1928
1929               <p>If <tt class="REPLACEABLE"><i>http_parent</i></tt> is
1930               <span class="QUOTE">"."</span>, then requests are not forwarded
1931               to another HTTP proxy but are made (HTTP-wise) directly to the
1932               web servers, albeit through a SOCKS proxy.</p>
1933             </dd>
1934
1935             <dt>Examples:</dt>
1936
1937             <dd>
1938               <p>From the company example.com, direct connections are made to
1939               all <span class="QUOTE">"internal"</span> domains, but
1940               everything outbound goes through their ISP's proxy by way of
1941               example.com's corporate SOCKS 4A gateway to the Internet.</p>
1942
1943               <table border="0" bgcolor="#E0E0E0" width="90%">
1944                 <tr>
1945                   <td>
1946                     <pre class="SCREEN">
1947   forward-socks4a   /              socks-gw.example.com:1080  www-cache.isp.example.net:8080
1948   forward           .example.com   .
1949 </pre>
1950                   </td>
1951                 </tr>
1952               </table>
1953
1954               <p>A rule that uses a SOCKS 4 gateway for all destinations but
1955               no HTTP parent looks like this:</p>
1956
1957               <table border="0" bgcolor="#E0E0E0" width="90%">
1958                 <tr>
1959                   <td>
1960                     <pre class="SCREEN">
1961   forward-socks4   /               socks-gw.example.com:1080  .
1962 </pre>
1963                   </td>
1964                 </tr>
1965               </table>
1966
1967               <p>To chain Privoxy and Tor, both running on the same system,
1968               you would use something like:</p>
1969
1970               <table border="0" bgcolor="#E0E0E0" width="90%">
1971                 <tr>
1972                   <td>
1973                     <pre class="SCREEN">
1974   forward-socks5   /               127.0.0.1:9050 .
1975 </pre>
1976                   </td>
1977                 </tr>
1978               </table>
1979
1980               <p>The public <span class="APPLICATION">Tor</span> network
1981               can't be used to reach your local network, if you need to
1982               access local servers you therefore might want to make some
1983               exceptions:</p>
1984
1985               <table border="0" bgcolor="#E0E0E0" width="90%">
1986                 <tr>
1987                   <td>
1988                     <pre class="SCREEN">
1989   forward         192.168.*.*/     .
1990   forward            10.*.*.*/     .
1991   forward           127.*.*.*/     .
1992 </pre>
1993                   </td>
1994                 </tr>
1995               </table>
1996
1997               <p>Unencrypted connections to systems in these address ranges
1998               will be as (un)secure as the local network is, but the
1999               alternative is that you can't reach the local network through
2000               <span class="APPLICATION">Privoxy</span> at all. Of course this
2001               may actually be desired and there is no reason to make these
2002               exceptions if you aren't sure you need them.</p>
2003
2004               <p>If you also want to be able to reach servers in your local
2005               network by using their names, you will need additional
2006               exceptions that look like this:</p>
2007
2008               <table border="0" bgcolor="#E0E0E0" width="90%">
2009                 <tr>
2010                   <td>
2011                     <pre class="SCREEN">
2012  forward           localhost/     .
2013 </pre>
2014                   </td>
2015                 </tr>
2016               </table>
2017             </dd>
2018           </dl>
2019         </div>
2020       </div>
2021
2022       <div class="SECT3">
2023         <h4 class="SECT3"><a name="ADVANCED-FORWARDING-EXAMPLES" id=
2024         "ADVANCED-FORWARDING-EXAMPLES">7.5.3. Advanced Forwarding
2025         Examples</a></h4>
2026
2027         <p>If you have links to multiple ISPs that provide various special
2028         content only to their subscribers, you can configure multiple
2029         <span class="APPLICATION">Privoxies</span> which have connections to
2030         the respective ISPs to act as forwarders to each other, so that
2031         <span class="emphasis"><i class="EMPHASIS">your</i></span> users can
2032         see the internal content of all ISPs.</p>
2033
2034         <p>Assume that host-a has a PPP connection to isp-a.example.net. And
2035         host-b has a PPP connection to isp-b.example.org. Both run
2036         <span class="APPLICATION">Privoxy</span>. Their forwarding
2037         configuration can look like this:</p>
2038
2039         <p>host-a:</p>
2040
2041         <table border="0" bgcolor="#E0E0E0" width="100%">
2042           <tr>
2043             <td>
2044               <pre class="SCREEN">
2045   forward    /           .
2046   forward    .isp-b.example.net  host-b:8118
2047 </pre>
2048             </td>
2049           </tr>
2050         </table>
2051
2052         <p>host-b:</p>
2053
2054         <table border="0" bgcolor="#E0E0E0" width="100%">
2055           <tr>
2056             <td>
2057               <pre class="SCREEN">
2058   forward    /           .
2059   forward    .isp-a.example.org  host-a:8118
2060 </pre>
2061             </td>
2062           </tr>
2063         </table>
2064
2065         <p>Now, your users can set their browser's proxy to use either host-a
2066         or host-b and be able to browse the internal content of both isp-a
2067         and isp-b.</p>
2068
2069         <p>If you intend to chain <span class="APPLICATION">Privoxy</span>
2070         and <span class="APPLICATION">squid</span> locally, then chaining as
2071         <tt class="LITERAL">browser -&gt; squid -&gt; privoxy</tt> is the
2072         recommended way.</p>
2073
2074         <p>Assuming that <span class="APPLICATION">Privoxy</span> and
2075         <span class="APPLICATION">squid</span> run on the same box, your
2076         <span class="APPLICATION">squid</span> configuration could then look
2077         like this:</p>
2078
2079         <table border="0" bgcolor="#E0E0E0" width="100%">
2080           <tr>
2081             <td>
2082               <pre class="SCREEN">
2083   # Define Privoxy as parent proxy (without ICP)
2084   cache_peer 127.0.0.1 parent 8118 7 no-query
2085
2086   # Define ACL for protocol FTP
2087   acl ftp proto FTP
2088
2089   # Do not forward FTP requests to Privoxy
2090   always_direct allow ftp
2091
2092   # Forward all the rest to Privoxy
2093   never_direct allow all
2094 </pre>
2095             </td>
2096           </tr>
2097         </table>
2098
2099         <p>You would then need to change your browser's proxy settings to
2100         <span class="APPLICATION">squid</span>'s address and port. Squid
2101         normally uses port 3128. If unsure consult <tt class=
2102         "LITERAL">http_port</tt> in <tt class="FILENAME">squid.conf</tt>.</p>
2103
2104         <p>You could just as well decide to only forward requests you suspect
2105         of leading to Windows executables through a virus-scanning parent
2106         proxy, say, on <tt class="LITERAL">antivir.example.com</tt>, port
2107         8010:</p>
2108
2109         <table border="0" bgcolor="#E0E0E0" width="100%">
2110           <tr>
2111             <td>
2112               <pre class="SCREEN">
2113   forward   /                          .
2114   forward   /.*\.(exe|com|dll|zip)$    antivir.example.com:8010
2115 </pre>
2116             </td>
2117           </tr>
2118         </table>
2119       </div>
2120
2121       <div class="SECT3">
2122         <h4 class="SECT3"><a name="FORWARDED-CONNECT-RETRIES" id=
2123         "FORWARDED-CONNECT-RETRIES">7.5.4. forwarded-connect-retries</a></h4>
2124
2125         <div class="VARIABLELIST">
2126           <dl>
2127             <dt>Specifies:</dt>
2128
2129             <dd>
2130               <p>How often Privoxy retries if a forwarded connection request
2131               fails.</p>
2132             </dd>
2133
2134             <dt>Type of value:</dt>
2135
2136             <dd>
2137               <p><tt class="REPLACEABLE"><i>Number of retries.</i></tt></p>
2138             </dd>
2139
2140             <dt>Default value:</dt>
2141
2142             <dd>
2143               <p><span class="emphasis"><i class="EMPHASIS">0</i></span></p>
2144             </dd>
2145
2146             <dt>Effect if unset:</dt>
2147
2148             <dd>
2149               <p>Connections forwarded through other proxies are treated like
2150               direct connections and no retry attempts are made.</p>
2151             </dd>
2152
2153             <dt>Notes:</dt>
2154
2155             <dd>
2156               <p><tt class=
2157               "REPLACEABLE"><i>forwarded-connect-retries</i></tt> is mainly
2158               interesting for socks4a connections, where <span class=
2159               "APPLICATION">Privoxy</span> can't detect why the connections
2160               failed. The connection might have failed because of a DNS
2161               timeout in which case a retry makes sense, but it might also
2162               have failed because the server doesn't exist or isn't
2163               reachable. In this case the retry will just delay the
2164               appearance of Privoxy's error message.</p>
2165
2166               <p>Note that in the context of this option, <span class=
2167               "QUOTE">"forwarded connections"</span> includes all connections
2168               that Privoxy forwards through other proxies. This option is not
2169               limited to the HTTP CONNECT method.</p>
2170
2171               <p>Only use this option, if you are getting lots of
2172               forwarding-related error messages that go away when you try
2173               again manually. Start with a small value and check Privoxy's
2174               logfile from time to time, to see how many retries are usually
2175               needed.</p>
2176             </dd>
2177
2178             <dt>Examples:</dt>
2179
2180             <dd>
2181               <p>forwarded-connect-retries 1</p>
2182             </dd>
2183           </dl>
2184         </div>
2185       </div>
2186     </div>
2187
2188     <div class="SECT2">
2189       <h2 class="SECT2"><a name="MISC" id="MISC">7.6. Miscellaneous</a></h2>
2190
2191       <div class="SECT3">
2192         <h4 class="SECT3"><a name="ACCEPT-INTERCEPTED-REQUESTS" id=
2193         "ACCEPT-INTERCEPTED-REQUESTS">7.6.1.
2194         accept-intercepted-requests</a></h4>
2195
2196         <div class="VARIABLELIST">
2197           <dl>
2198             <dt>Specifies:</dt>
2199
2200             <dd>
2201               <p>Whether intercepted requests should be treated as valid.</p>
2202             </dd>
2203
2204             <dt>Type of value:</dt>
2205
2206             <dd>
2207               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2208             </dd>
2209
2210             <dt>Default value:</dt>
2211
2212             <dd>
2213               <p><span class="emphasis"><i class="EMPHASIS">0</i></span></p>
2214             </dd>
2215
2216             <dt>Effect if unset:</dt>
2217
2218             <dd>
2219               <p>Only proxy requests are accepted, intercepted requests are
2220               treated as invalid.</p>
2221             </dd>
2222
2223             <dt>Notes:</dt>
2224
2225             <dd>
2226               <p>If you don't trust your clients and want to force them to
2227               use <span class="APPLICATION">Privoxy</span>, enable this
2228               option and configure your packet filter to redirect outgoing
2229               HTTP connections into <span class=
2230               "APPLICATION">Privoxy</span>.</p>
2231
2232               <p>Make sure that <span class="APPLICATION">Privoxy's</span>
2233               own requests aren't redirected as well. Additionally take care
2234               that <span class="APPLICATION">Privoxy</span> can't
2235               intentionally connect to itself, otherwise you could run into
2236               redirection loops if <span class="APPLICATION">Privoxy's</span>
2237               listening port is reachable by the outside or an attacker has
2238               access to the pages you visit.</p>
2239             </dd>
2240
2241             <dt>Examples:</dt>
2242
2243             <dd>
2244               <p>accept-intercepted-requests 1</p>
2245             </dd>
2246           </dl>
2247         </div>
2248       </div>
2249
2250       <div class="SECT3">
2251         <h4 class="SECT3"><a name="ALLOW-CGI-REQUEST-CRUNCHING" id=
2252         "ALLOW-CGI-REQUEST-CRUNCHING">7.6.2.
2253         allow-cgi-request-crunching</a></h4>
2254
2255         <div class="VARIABLELIST">
2256           <dl>
2257             <dt>Specifies:</dt>
2258
2259             <dd>
2260               <p>Whether requests to <span class=
2261               "APPLICATION">Privoxy's</span> CGI pages can be blocked or
2262               redirected.</p>
2263             </dd>
2264
2265             <dt>Type of value:</dt>
2266
2267             <dd>
2268               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2269             </dd>
2270
2271             <dt>Default value:</dt>
2272
2273             <dd>
2274               <p><span class="emphasis"><i class="EMPHASIS">0</i></span></p>
2275             </dd>
2276
2277             <dt>Effect if unset:</dt>
2278
2279             <dd>
2280               <p><span class="APPLICATION">Privoxy</span> ignores block and
2281               redirect actions for its CGI pages.</p>
2282             </dd>
2283
2284             <dt>Notes:</dt>
2285
2286             <dd>
2287               <p>By default <span class="APPLICATION">Privoxy</span> ignores
2288               block or redirect actions for its CGI pages. Intercepting these
2289               requests can be useful in multi-user setups to implement
2290               fine-grained access control, but it can also render the
2291               complete web interface useless and make debugging problems
2292               painful if done without care.</p>
2293
2294               <p>Don't enable this option unless you're sure that you really
2295               need it.</p>
2296             </dd>
2297
2298             <dt>Examples:</dt>
2299
2300             <dd>
2301               <p>allow-cgi-request-crunching 1</p>
2302             </dd>
2303           </dl>
2304         </div>
2305       </div>
2306
2307       <div class="SECT3">
2308         <h4 class="SECT3"><a name="SPLIT-LARGE-FORMS" id=
2309         "SPLIT-LARGE-FORMS">7.6.3. split-large-forms</a></h4>
2310
2311         <div class="VARIABLELIST">
2312           <dl>
2313             <dt>Specifies:</dt>
2314
2315             <dd>
2316               <p>Whether the CGI interface should stay compatible with broken
2317               HTTP clients.</p>
2318             </dd>
2319
2320             <dt>Type of value:</dt>
2321
2322             <dd>
2323               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2324             </dd>
2325
2326             <dt>Default value:</dt>
2327
2328             <dd>
2329               <p><span class="emphasis"><i class="EMPHASIS">0</i></span></p>
2330             </dd>
2331
2332             <dt>Effect if unset:</dt>
2333
2334             <dd>
2335               <p>The CGI form generate long GET URLs.</p>
2336             </dd>
2337
2338             <dt>Notes:</dt>
2339
2340             <dd>
2341               <p><span class="APPLICATION">Privoxy's</span> CGI forms can
2342               lead to rather long URLs. This isn't a problem as far as the
2343               HTTP standard is concerned, but it can confuse clients with
2344               arbitrary URL length limitations.</p>
2345
2346               <p>Enabling split-large-forms causes <span class=
2347               "APPLICATION">Privoxy</span> to divide big forms into smaller
2348               ones to keep the URL length down. It makes editing a lot less
2349               convenient and you can no longer submit all changes at once,
2350               but at least it works around this browser bug.</p>
2351
2352               <p>If you don't notice any editing problems, there is no reason
2353               to enable this option, but if one of the submit buttons appears
2354               to be broken, you should give it a try.</p>
2355             </dd>
2356
2357             <dt>Examples:</dt>
2358
2359             <dd>
2360               <p>split-large-forms 1</p>
2361             </dd>
2362           </dl>
2363         </div>
2364       </div>
2365
2366       <div class="SECT3">
2367         <h4 class="SECT3"><a name="KEEP-ALIVE-TIMEOUT" id=
2368         "KEEP-ALIVE-TIMEOUT">7.6.4. keep-alive-timeout</a></h4>
2369
2370         <div class="VARIABLELIST">
2371           <dl>
2372             <dt>Specifies:</dt>
2373
2374             <dd>
2375               <p>Number of seconds after which an open connection will no
2376               longer be reused.</p>
2377             </dd>
2378
2379             <dt>Type of value:</dt>
2380
2381             <dd>
2382               <p><tt class="REPLACEABLE"><i>Time in seconds.</i></tt></p>
2383             </dd>
2384
2385             <dt>Default value:</dt>
2386
2387             <dd>
2388               <p>None</p>
2389             </dd>
2390
2391             <dt>Effect if unset:</dt>
2392
2393             <dd>
2394               <p>Connections are not kept alive.</p>
2395             </dd>
2396
2397             <dt>Notes:</dt>
2398
2399             <dd>
2400               <p>This option allows clients to keep the connection to
2401               <span class="APPLICATION">Privoxy</span> alive. If the server
2402               supports it, <span class="APPLICATION">Privoxy</span> will keep
2403               the connection to the server alive as well. Under certain
2404               circumstances this may result in speed-ups.</p>
2405
2406               <p>By default, <span class="APPLICATION">Privoxy</span> will
2407               close the connection to the server if the client connection
2408               gets closed, or if the specified timeout has been reached
2409               without a new request coming in. This behaviour can be changed
2410               with the <a href="#CONNECTION-SHARING" target=
2411               "_top">connection-sharing</a> option.</p>
2412
2413               <p>This option has no effect if <span class=
2414               "APPLICATION">Privoxy</span> has been compiled without
2415               keep-alive support.</p>
2416
2417               <p>Note that a timeout of five seconds as used in the default
2418               configuration file significantly decreases the number of
2419               connections that will be reused. The value is used because some
2420               browsers limit the number of connections they open to a single
2421               host and apply the same limit to proxies. This can result in a
2422               single website <span class="QUOTE">"grabbing"</span> all the
2423               connections the browser allows, which means connections to
2424               other websites can't be opened until the connections currently
2425               in use time out.</p>
2426
2427               <p>Several users have reported this as a Privoxy bug, so the
2428               default value has been reduced. Consider increasing it to 300
2429               seconds or even more if you think your browser can handle it.
2430               If your browser appears to be hanging, it probably can't.</p>
2431             </dd>
2432
2433             <dt>Examples:</dt>
2434
2435             <dd>
2436               <p>keep-alive-timeout 300</p>
2437             </dd>
2438           </dl>
2439         </div>
2440       </div>
2441
2442       <div class="SECT3">
2443         <h4 class="SECT3"><a name="TOLERATE-PIPELINING" id=
2444         "TOLERATE-PIPELINING">7.6.5. tolerate-pipelining</a></h4>
2445
2446         <div class="VARIABLELIST">
2447           <dl>
2448             <dt>Specifies:</dt>
2449
2450             <dd>
2451               <p>Whether or not pipelined requests should be served.</p>
2452             </dd>
2453
2454             <dt>Type of value:</dt>
2455
2456             <dd>
2457               <p><tt class="REPLACEABLE"><i>0 or 1.</i></tt></p>
2458             </dd>
2459
2460             <dt>Default value:</dt>
2461
2462             <dd>
2463               <p>None</p>
2464             </dd>
2465
2466             <dt>Effect if unset:</dt>
2467
2468             <dd>
2469               <p>If Privoxy receives more than one request at once, it
2470               terminates the client connection after serving the first
2471               one.</p>
2472             </dd>
2473
2474             <dt>Notes:</dt>
2475
2476             <dd>
2477               <p><span class="APPLICATION">Privoxy</span> currently doesn't
2478               pipeline outgoing requests, thus allowing pipelining on the
2479               client connection is not guaranteed to improve the
2480               performance.</p>
2481
2482               <p>By default <span class="APPLICATION">Privoxy</span> tries to
2483               discourage clients from pipelining by discarding aggressively
2484               pipelined requests, which forces the client to resend them
2485               through a new connection.</p>
2486
2487               <p>This option lets <span class="APPLICATION">Privoxy</span>
2488               tolerate pipelining. Whether or not that improves performance
2489               mainly depends on the client configuration.</p>
2490
2491               <p>If you are seeing problems with pages not properly loading,
2492               disabling this option could work around the problem.</p>
2493             </dd>
2494
2495             <dt>Examples:</dt>
2496
2497             <dd>
2498               <p>tolerate-pipelining 1</p>
2499             </dd>
2500           </dl>
2501         </div>
2502       </div>
2503
2504       <div class="SECT3">
2505         <h4 class="SECT3"><a name="DEFAULT-SERVER-TIMEOUT" id=
2506         "DEFAULT-SERVER-TIMEOUT">7.6.6. default-server-timeout</a></h4>
2507
2508         <div class="VARIABLELIST">
2509           <dl>
2510             <dt>Specifies:</dt>
2511
2512             <dd>
2513               <p>Assumed server-side keep-alive timeout if not specified by
2514               the server.</p>
2515             </dd>
2516
2517             <dt>Type of value:</dt>
2518
2519             <dd>
2520               <p><tt class="REPLACEABLE"><i>Time in seconds.</i></tt></p>
2521             </dd>
2522
2523             <dt>Default value:</dt>
2524
2525             <dd>
2526               <p>None</p>
2527             </dd>
2528
2529             <dt>Effect if unset:</dt>
2530
2531             <dd>
2532               <p>Connections for which the server didn't specify the
2533               keep-alive timeout are not reused.</p>
2534             </dd>
2535
2536             <dt>Notes:</dt>
2537
2538             <dd>
2539               <p>Enabling this option significantly increases the number of
2540               connections that are reused, provided the <a href=
2541               "#KEEP-ALIVE-TIMEOUT" target="_top">keep-alive-timeout</a>
2542               option is also enabled.</p>
2543
2544               <p>While it also increases the number of connections problems
2545               when <span class="APPLICATION">Privoxy</span> tries to reuse a
2546               connection that already has been closed on the server side, or
2547               is closed while <span class="APPLICATION">Privoxy</span> is
2548               trying to reuse it, this should only be a problem if it happens
2549               for the first request sent by the client. If it happens for
2550               requests on reused client connections, <span class=
2551               "APPLICATION">Privoxy</span> will simply close the connection
2552               and the client is supposed to retry the request without
2553               bothering the user.</p>
2554
2555               <p>Enabling this option is therefore only recommended if the
2556               <a href="#CONNECTION-SHARING" target=
2557               "_top">connection-sharing</a> option is disabled.</p>
2558
2559               <p>It is an error to specify a value larger than the <a href=
2560               "#KEEP-ALIVE-TIMEOUT" target="_top">keep-alive-timeout</a>
2561               value.</p>
2562
2563               <p>This option has no effect if <span class=
2564               "APPLICATION">Privoxy</span> has been compiled without
2565               keep-alive support.</p>
2566             </dd>
2567
2568             <dt>Examples:</dt>
2569
2570             <dd>
2571               <p>default-server-timeout 60</p>
2572             </dd>
2573           </dl>
2574         </div>
2575       </div>
2576
2577       <div class="SECT3">
2578         <h4 class="SECT3"><a name="CONNECTION-SHARING" id=
2579         "CONNECTION-SHARING">7.6.7. connection-sharing</a></h4>
2580
2581         <div class="VARIABLELIST">
2582           <dl>
2583             <dt>Specifies:</dt>
2584
2585             <dd>
2586               <p>Whether or not outgoing connections that have been kept
2587               alive should be shared between different incoming
2588               connections.</p>
2589             </dd>
2590
2591             <dt>Type of value:</dt>
2592
2593             <dd>
2594               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2595             </dd>
2596
2597             <dt>Default value:</dt>
2598
2599             <dd>
2600               <p>None</p>
2601             </dd>
2602
2603             <dt>Effect if unset:</dt>
2604
2605             <dd>
2606               <p>Connections are not shared.</p>
2607             </dd>
2608
2609             <dt>Notes:</dt>
2610
2611             <dd>
2612               <p>This option has no effect if <span class=
2613               "APPLICATION">Privoxy</span> has been compiled without
2614               keep-alive support, or if it's disabled.</p>
2615             </dd>
2616
2617             <dt>Notes:</dt>
2618
2619             <dd>
2620               <p>Note that reusing connections doesn't necessary cause
2621               speedups. There are also a few privacy implications you should
2622               be aware of.</p>
2623
2624               <p>If this option is effective, outgoing connections are shared
2625               between clients (if there are more than one) and closing the
2626               browser that initiated the outgoing connection does no longer
2627               affect the connection between <span class=
2628               "APPLICATION">Privoxy</span> and the server unless the client's
2629               request hasn't been completed yet.</p>
2630
2631               <p>If the outgoing connection is idle, it will not be closed
2632               until either <span class="APPLICATION">Privoxy's</span> or the
2633               server's timeout is reached. While it's open, the server knows
2634               that the system running <span class=
2635               "APPLICATION">Privoxy</span> is still there.</p>
2636
2637               <p>If there are more than one client (maybe even belonging to
2638               multiple users), they will be able to reuse each others
2639               connections. This is potentially dangerous in case of
2640               authentication schemes like NTLM where only the connection is
2641               authenticated, instead of requiring authentication for each
2642               request.</p>
2643
2644               <p>If there is only a single client, and if said client can
2645               keep connections alive on its own, enabling this option has
2646               next to no effect. If the client doesn't support connection
2647               keep-alive, enabling this option may make sense as it allows
2648               <span class="APPLICATION">Privoxy</span> to keep outgoing
2649               connections alive even if the client itself doesn't support
2650               it.</p>
2651
2652               <p>You should also be aware that enabling this option increases
2653               the likelihood of getting the "No server or forwarder data"
2654               error message, especially if you are using a slow connection to
2655               the Internet.</p>
2656
2657               <p>This option should only be used by experienced users who
2658               understand the risks and can weight them against the
2659               benefits.</p>
2660             </dd>
2661
2662             <dt>Examples:</dt>
2663
2664             <dd>
2665               <p>connection-sharing 1</p>
2666             </dd>
2667           </dl>
2668         </div>
2669       </div>
2670
2671       <div class="SECT3">
2672         <h4 class="SECT3"><a name="SOCKET-TIMEOUT" id="SOCKET-TIMEOUT">7.6.8.
2673         socket-timeout</a></h4>
2674
2675         <div class="VARIABLELIST">
2676           <dl>
2677             <dt>Specifies:</dt>
2678
2679             <dd>
2680               <p>Number of seconds after which a socket times out if no data
2681               is received.</p>
2682             </dd>
2683
2684             <dt>Type of value:</dt>
2685
2686             <dd>
2687               <p><tt class="REPLACEABLE"><i>Time in seconds.</i></tt></p>
2688             </dd>
2689
2690             <dt>Default value:</dt>
2691
2692             <dd>
2693               <p>None</p>
2694             </dd>
2695
2696             <dt>Effect if unset:</dt>
2697
2698             <dd>
2699               <p>A default value of 300 seconds is used.</p>
2700             </dd>
2701
2702             <dt>Notes:</dt>
2703
2704             <dd>
2705               <p>The default is quite high and you probably want to reduce
2706               it. If you aren't using an occasionally slow proxy like Tor,
2707               reducing it to a few seconds should be fine.</p>
2708             </dd>
2709
2710             <dt>Examples:</dt>
2711
2712             <dd>
2713               <p>socket-timeout 300</p>
2714             </dd>
2715           </dl>
2716         </div>
2717       </div>
2718
2719       <div class="SECT3">
2720         <h4 class="SECT3"><a name="MAX-CLIENT-CONNECTIONS" id=
2721         "MAX-CLIENT-CONNECTIONS">7.6.9. max-client-connections</a></h4>
2722
2723         <div class="VARIABLELIST">
2724           <dl>
2725             <dt>Specifies:</dt>
2726
2727             <dd>
2728               <p>Maximum number of client connections that will be
2729               served.</p>
2730             </dd>
2731
2732             <dt>Type of value:</dt>
2733
2734             <dd>
2735               <p><tt class="REPLACEABLE"><i>Positive number.</i></tt></p>
2736             </dd>
2737
2738             <dt>Default value:</dt>
2739
2740             <dd>
2741               <p>128</p>
2742             </dd>
2743
2744             <dt>Effect if unset:</dt>
2745
2746             <dd>
2747               <p>Connections are served until a resource limit is
2748               reached.</p>
2749             </dd>
2750
2751             <dt>Notes:</dt>
2752
2753             <dd>
2754               <p><span class="APPLICATION">Privoxy</span> creates one thread
2755               (or process) for every incoming client connection that isn't
2756               rejected based on the access control settings.</p>
2757
2758               <p>If the system is powerful enough, <span class=
2759               "APPLICATION">Privoxy</span> can theoretically deal with
2760               several hundred (or thousand) connections at the same time, but
2761               some operating systems enforce resource limits by shutting down
2762               offending processes and their default limits may be below the
2763               ones <span class="APPLICATION">Privoxy</span> would require
2764               under heavy load.</p>
2765
2766               <p>Configuring <span class="APPLICATION">Privoxy</span> to
2767               enforce a connection limit below the thread or process limit
2768               used by the operating system makes sure this doesn't happen.
2769               Simply increasing the operating system's limit would work too,
2770               but if <span class="APPLICATION">Privoxy</span> isn't the only
2771               application running on the system, you may actually want to
2772               limit the resources used by <span class=
2773               "APPLICATION">Privoxy</span>.</p>
2774
2775               <p>If <span class="APPLICATION">Privoxy</span> is only used by
2776               a single trusted user, limiting the number of client
2777               connections is probably unnecessary. If there are multiple
2778               possibly untrusted users you probably still want to
2779               additionally use a packet filter to limit the maximal number of
2780               incoming connections per client. Otherwise a malicious user
2781               could intentionally create a high number of connections to
2782               prevent other users from using <span class=
2783               "APPLICATION">Privoxy</span>.</p>
2784
2785               <p>Obviously using this option only makes sense if you choose a
2786               limit below the one enforced by the operating system.</p>
2787
2788               <p>One most POSIX-compliant systems <span class=
2789               "APPLICATION">Privoxy</span> can't properly deal with more than
2790               FD_SETSIZE file descriptors at the same time and has to reject
2791               connections if the limit is reached. This will likely change in
2792               a future version, but currently this limit can't be increased
2793               without recompiling <span class="APPLICATION">Privoxy</span>
2794               with a different FD_SETSIZE limit.</p>
2795             </dd>
2796
2797             <dt>Examples:</dt>
2798
2799             <dd>
2800               <p>max-client-connections 256</p>
2801             </dd>
2802           </dl>
2803         </div>
2804       </div>
2805
2806       <div class="SECT3">
2807         <h4 class="SECT3"><a name="HANDLE-AS-EMPTY-DOC-RETURNS-OK" id=
2808         "HANDLE-AS-EMPTY-DOC-RETURNS-OK">7.6.10.
2809         handle-as-empty-doc-returns-ok</a></h4>
2810
2811         <div class="VARIABLELIST">
2812           <dl>
2813             <dt>Specifies:</dt>
2814
2815             <dd>
2816               <p>The status code Privoxy returns for pages blocked with
2817               <tt class="LITERAL"><a href=
2818               "actions-file.html#HANDLE-AS-EMPTY-DOCUMENT" target=
2819               "_top">+handle-as-empty-document</a></tt>.</p>
2820             </dd>
2821
2822             <dt>Type of value:</dt>
2823
2824             <dd>
2825               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2826             </dd>
2827
2828             <dt>Default value:</dt>
2829
2830             <dd>
2831               <p>0</p>
2832             </dd>
2833
2834             <dt>Effect if unset:</dt>
2835
2836             <dd>
2837               <p>Privoxy returns a status 403(forbidden) for all blocked
2838               pages.</p>
2839             </dd>
2840
2841             <dt>Effect if set:</dt>
2842
2843             <dd>
2844               <p>Privoxy returns a status 200(OK) for pages blocked with
2845               +handle-as-empty-document and a status 403(Forbidden) for all
2846               other blocked pages.</p>
2847             </dd>
2848
2849             <dt>Notes:</dt>
2850
2851             <dd>
2852               <p>This is a work-around for Firefox bug 492459: <span class=
2853               "QUOTE">" Websites are no longer rendered if SSL requests for
2854               JavaScripts are blocked by a proxy. "</span> (<a href=
2855               "https://bugzilla.mozilla.org/show_bug.cgi?id=492459" target=
2856               "_top">https://bugzilla.mozilla.org/show_bug.cgi?id=492459</a>)
2857               As the bug has been fixed for quite some time this option
2858               should no longer be needed and will be removed in a future
2859               release. Please speak up if you have a reason why the option
2860               should be kept around.</p>
2861             </dd>
2862           </dl>
2863         </div>
2864       </div>
2865
2866       <div class="SECT3">
2867         <h4 class="SECT3"><a name="ENABLE-COMPRESSION" id=
2868         "ENABLE-COMPRESSION">7.6.11. enable-compression</a></h4>
2869
2870         <div class="VARIABLELIST">
2871           <dl>
2872             <dt>Specifies:</dt>
2873
2874             <dd>
2875               <p>Whether or not buffered content is compressed before
2876               delivery.</p>
2877             </dd>
2878
2879             <dt>Type of value:</dt>
2880
2881             <dd>
2882               <p><tt class="REPLACEABLE"><i>0 or 1</i></tt></p>
2883             </dd>
2884
2885             <dt>Default value:</dt>
2886
2887             <dd>
2888               <p>0</p>
2889             </dd>
2890
2891             <dt>Effect if unset:</dt>
2892
2893             <dd>
2894               <p>Privoxy does not compress buffered content.</p>
2895             </dd>
2896
2897             <dt>Effect if set:</dt>
2898
2899             <dd>
2900               <p>Privoxy compresses buffered content before delivering it to
2901               the client, provided the client supports it.</p>
2902             </dd>
2903
2904             <dt>Notes:</dt>
2905
2906             <dd>
2907               <p>This directive is only supported if Privoxy has been
2908               compiled with FEATURE_COMPRESSION, which should not to be
2909               confused with FEATURE_ZLIB.</p>
2910
2911               <p>Compressing buffered content is mainly useful if Privoxy and
2912               the client are running on different systems. If they are
2913               running on the same system, enabling compression is likely to
2914               slow things down. If you didn't measure otherwise, you should
2915               assume that it does and keep this option disabled.</p>
2916
2917               <p>Privoxy will not compress buffered content below a certain
2918               length.</p>
2919             </dd>
2920           </dl>
2921         </div>
2922       </div>
2923
2924       <div class="SECT3">
2925         <h4 class="SECT3"><a name="COMPRESSION-LEVEL" id=
2926         "COMPRESSION-LEVEL">7.6.12. compression-level</a></h4>
2927
2928         <div class="VARIABLELIST">
2929           <dl>
2930             <dt>Specifies:</dt>
2931
2932             <dd>
2933               <p>The compression level that is passed to the zlib library
2934               when compressing buffered content.</p>
2935             </dd>
2936
2937             <dt>Type of value:</dt>
2938
2939             <dd>
2940               <p><tt class="REPLACEABLE"><i>Positive number ranging from 0 to
2941               9.</i></tt></p>
2942             </dd>
2943
2944             <dt>Default value:</dt>
2945
2946             <dd>
2947               <p>1</p>
2948             </dd>
2949
2950             <dt>Notes:</dt>
2951
2952             <dd>
2953               <p>Compressing the data more takes usually longer than
2954               compressing it less or not compressing it at all. Which level
2955               is best depends on the connection between Privoxy and the
2956               client. If you can't be bothered to benchmark it for yourself,
2957               you should stick with the default and keep compression
2958               disabled.</p>
2959
2960               <p>If compression is disabled, the compression level is
2961               irrelevant.</p>
2962             </dd>
2963
2964             <dt>Examples:</dt>
2965
2966             <dd>
2967               <table border="0" bgcolor="#E0E0E0" width="90%">
2968                 <tr>
2969                   <td>
2970                     <pre class="SCREEN">
2971     # Best speed (compared to the other levels)
2972     compression-level 1
2973     # Best compression
2974     compression-level 9
2975     # No compression. Only useful for testing as the added header
2976     # slightly increases the amount of data that has to be sent.
2977     # If your benchmark shows that using this compression level
2978     # is superior to using no compression at all, the benchmark
2979     # is likely to be flawed.
2980     compression-level 0
2981
2982 </pre>
2983                   </td>
2984                 </tr>
2985               </table>
2986             </dd>
2987           </dl>
2988         </div>
2989       </div>
2990
2991       <div class="SECT3">
2992         <h4 class="SECT3"><a name="CLIENT-HEADER-ORDER" id=
2993         "CLIENT-HEADER-ORDER">7.6.13. client-header-order</a></h4>
2994
2995         <div class="VARIABLELIST">
2996           <dl>
2997             <dt>Specifies:</dt>
2998
2999             <dd>
3000               <p>The order in which client headers are sorted before
3001               forwarding them.</p>
3002             </dd>
3003
3004             <dt>Type of value:</dt>
3005
3006             <dd>
3007               <p><tt class="REPLACEABLE"><i>Client header names delimited by
3008               spaces or tabs</i></tt></p>
3009             </dd>
3010
3011             <dt>Default value:</dt>
3012
3013             <dd>
3014               <p>None</p>
3015             </dd>
3016
3017             <dt>Notes:</dt>
3018
3019             <dd>
3020               <p>By default <span class="APPLICATION">Privoxy</span> leaves
3021               the client headers in the order they were sent by the client.
3022               Headers are modified in-place, new headers are added at the end
3023               of the already existing headers.</p>
3024
3025               <p>The header order can be used to fingerprint client requests
3026               independently of other headers like the User-Agent.</p>
3027
3028               <p>This directive allows to sort the headers differently to
3029               better mimic a different User-Agent. Client headers will be
3030               emitted in the order given, headers whose name isn't explicitly
3031               specified are added at the end.</p>
3032
3033               <p>Note that sorting headers in an uncommon way will make
3034               fingerprinting actually easier. Encrypted headers are not
3035               affected by this directive.</p>
3036             </dd>
3037           </dl>
3038         </div>
3039       </div>
3040     </div>
3041
3042     <div class="SECT2">
3043       <h2 class="SECT2"><a name="WINDOWS-GUI" id="WINDOWS-GUI">7.7. Windows
3044       GUI Options</a></h2>
3045
3046       <p><span class="APPLICATION">Privoxy</span> has a number of options
3047       specific to the Windows GUI interface:</p><a name="ACTIVITY-ANIMATION"
3048       id="ACTIVITY-ANIMATION"></a>
3049
3050       <p>If <span class="QUOTE">"activity-animation"</span> is set to 1, the
3051       <span class="APPLICATION">Privoxy</span> icon will animate when
3052       <span class="QUOTE">"Privoxy"</span> is active. To turn off, set to
3053       0.</p>
3054
3055       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3056       "emphasis"><i class="EMPHASIS">activity-animation 1</i></span><br>
3057       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-MESSAGES" id=
3058       "LOG-MESSAGES"></a>
3059
3060       <p>If <span class="QUOTE">"log-messages"</span> is set to 1,
3061       <span class="APPLICATION">Privoxy</span> copies log messages to the
3062       console window. The log detail depends on the <a href=
3063       "config.html#DEBUG">debug</a> directive.</p>
3064
3065       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3066       "emphasis"><i class="EMPHASIS">log-messages 1</i></span><br>
3067       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-BUFFER-SIZE" id=
3068       "LOG-BUFFER-SIZE"></a>
3069
3070       <p>If <span class="QUOTE">"log-buffer-size"</span> is set to 1, the
3071       size of the log buffer, i.e. the amount of memory used for the log
3072       messages displayed in the console window, will be limited to
3073       <span class="QUOTE">"log-max-lines"</span> (see below).</p>
3074
3075       <p>Warning: Setting this to 0 will result in the buffer to grow
3076       infinitely and eat up all your memory!</p>
3077
3078       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3079       "emphasis"><i class="EMPHASIS">log-buffer-size 1</i></span><br>
3080       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-MAX-LINES" id=
3081       "LOG-MAX-LINES"></a>
3082
3083       <p><span class="APPLICATION">log-max-lines</span> is the maximum number
3084       of lines held in the log buffer. See above.</p>
3085
3086       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3087       "emphasis"><i class="EMPHASIS">log-max-lines 200</i></span><br>
3088       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-HIGHLIGHT-MESSAGES" id=
3089       "LOG-HIGHLIGHT-MESSAGES"></a>
3090
3091       <p>If <span class="QUOTE">"log-highlight-messages"</span> is set to 1,
3092       <span class="APPLICATION">Privoxy</span> will highlight portions of the
3093       log messages with a bold-faced font:</p>
3094
3095       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3096       "emphasis"><i class="EMPHASIS">log-highlight-messages 1</i></span><br>
3097       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-FONT-NAME" id=
3098       "LOG-FONT-NAME"></a>
3099
3100       <p>The font used in the console window:</p>
3101
3102       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3103       "emphasis"><i class="EMPHASIS">log-font-name Comic Sans
3104       MS</i></span><br>
3105       &nbsp;&nbsp;&nbsp;</tt></p><a name="LOG-FONT-SIZE" id=
3106       "LOG-FONT-SIZE"></a>
3107
3108       <p>Font size used in the console window:</p>
3109
3110       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3111       "emphasis"><i class="EMPHASIS">log-font-size 8</i></span><br>
3112       &nbsp;&nbsp;&nbsp;</tt></p><a name="SHOW-ON-TASK-BAR" id=
3113       "SHOW-ON-TASK-BAR"></a>
3114
3115       <p><span class="QUOTE">"show-on-task-bar"</span> controls whether or
3116       not <span class="APPLICATION">Privoxy</span> will appear as a button on
3117       the Task bar when minimized:</p>
3118
3119       <p class="LITERALLAYOUT"><tt class="LITERAL">&nbsp;&nbsp;<span class=
3120       "emphasis"><i class="EMPHASIS">show-on-task-bar 0</i></span><br>
3121       &nbsp;&nbsp;&nbsp;</tt></p><a name="CLOSE-BUTTON-MINIMIZES" id=
3122       "CLOSE-BUTTON-MINIMIZES"></a>
3123
3124       <p>If <span class="QUOTE">"close-button-minimizes"</span> is set to 1,
3125       the Windows close button will minimize <span class=
3126       "APPLICATION">Privoxy</span> instead of closing the program (close with
3127       the exit option on the File menu).</p>