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43 >Privoxy Frequently Asked Questions</TH
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80 >1. General Information</A
88 >1.1. Who should give <SPAN
94 > Anyone who is interested in security, privacy, or in
95 finer-grained control over their web and Internet experience.
104 >1.2. Is Privoxy the best choice for
111 > is certainly a good choice, especially for those who want more
112 control and security. Those with the willingness to read the documentation
113 and the ability to fine-tune their installation will benefit the most.
120 strengths is that it is highly configurable giving you the ability to
121 completely personalize your installation. Being familiar with, or at least
122 having an interest in learning about <A
123 HREF="http://en.wikipedia.org/wiki/Http"
126 > and other networking
128 HREF="http://en.wikipedia.org/wiki/Html"
133 HREF="http://en.wikipedia.org/wiki/Regular_expressions"
141 will be a big plus and will help you get the most out of <SPAN
145 A new installation just includes a very basic configuration. The user
146 should take this as a starting point only, and enhance it as he or she
147 sees fit. In fact, the user is encouraged, and expected to, fine-tune the
154 > configuration can be done
156 HREF="http://en.wikipedia.org/wiki/Web_browser"
160 But there are areas where configuration is done using a
162 HREF="http://en.wikipedia.org/wiki/Text_editors"
166 to edit configuration files. Also note that the web-based action editor
167 doesn't use authentication and should only be enabled in environments
168 where all clients with access to <SPAN
171 > listening port can be trusted.
180 >1.3. What is a <SPAN
188 HREF="http://en.wikipedia.org/wiki/Proxy_server"
192 is a service, based on a software such as <SPAN
196 (i.e. browsers) can use instead of connecting to web servers directly.
197 The clients then ask the proxy to request objects (web pages, images, movies etc)
198 on their behalf and to forward the data to the clients.
204 HREF="http://en.wikipedia.org/wiki/Proxy_server"
206 >Wikipedia's proxy definition</A
210 > There are many reasons to use web proxies, such as security (firewalling),
211 efficiency (caching) and others, and there are any number of proxies
212 to accommodate those needs.
218 > is a proxy that is primarily focused on
219 privacy enhancement, ad and junk elimination and freeing the user from
220 restrictions placed on his activities. Sitting between your browser(s) and the Internet,
221 it is in a perfect position to filter outbound personal information that your
222 browser is leaking, as well as inbound junk. It uses a variety of techniques to do
223 this, all of which are under your complete control via the various configuration
224 files and options. Being a proxy also makes it easier to share
225 configurations among multiple browsers and/or users.
234 >1.4. Does Privoxy do anything more than ad blocking?</A
238 Yes, ad blocking is but one possible use. There are many, many ways <SPAN
242 can be used to sanitize and customize web browsing. </P
250 >1.5. What is this new version of
257 > A long time ago, there was the
259 HREF="http://www.junkbusters.com/ijb.html"
263 >Internet Junkbuster</SPAN
266 by Anonymous Coders and <A
267 HREF="http://www.junkbusters.com/"
271 >. This saved many users a lot of pain in the early days of
272 web advertising and user tracking.</P
274 > But the web, its protocols and standards, and with it, the techniques for
275 forcing ads on users, give up autonomy over their browsing, and
276 for tracking them, keeps evolving. Unfortunately, the <SPAN
280 > did not. Version 2.0.2, published in 1998, was
281 (and is) the last official
283 HREF="http://www.junkbusters.com/ijbdist.html#release"
288 HREF="http://www.junkbusters.com"
290 >Junkbusters Corporation</A
292 Fortunately, it had been released under the GNU
294 HREF="http://www.gnu.org/licenses/gpl.html"
297 >, which allowed further
298 development by others.</P
300 > So Stefan Waldherr started maintaining an
302 HREF="http://www.waldherr.org/junkbuster/"
304 >improved version of the
306 >, to which eventually a number of people contributed patches.
307 It could already replace banners with a transparent image, and had a first
308 version of pop-up killing, but it was still very closely based on the
309 original, with all its limitations, such as the lack of HTTP/1.1 support,
310 flexible per-site configuration, or content modification. The last release
311 from this effort was version 2.0.2-10, published in 2000.</P
315 HREF="http://www.privoxy.org/user-manual/copyright.html#AUTHORS"
319 picked up the thread, and started turning the software inside out, upside down,
320 and then reassembled it, adding many
322 HREF="http://www.privoxy.org/user-manual/introduction.html#FEATURES"
328 > The result of this is <SPAN
332 stable version, 3.0, was released August, 2002.
344 >? Why change the name from
345 Junkbuster at all?</A
348 > Though outdated, <A
349 HREF="http://junkbusters.com/"
351 >Junkbusters Corporation</A
353 continues to offer their original version of the <SPAN
361 >-derived software under the same name
364 > There are also potential legal complications from our use of the
368 > name, which is a registered trademark of
370 HREF="http://junkbusters.com/"
372 >Junkbusters Corporation</A
374 There are, however, no objections from Junkbusters Corporation to the
378 > project itself, and they, in fact, still
379 share our ideals and goals.</P
381 > The developers also believed that there are so many improvements over the original
382 code, that it was time to make a clean break from the past and make
383 a name in their own right.</P
395 >Privacy Enhancing Proxy</I
399 modification and junk suppression gives <SPAN
406 control, more freedom, and allows you to browse your personal and
424 >1.7. How does Privoxy differ
425 from the old Junkbuster?</A
439 > still blocks ads and banners,
441 HREF="http://en.wikipedia.org/wiki/Browser_cookie"
445 helps protect your privacy. But, most of these features have been enhanced,
446 and many new ones have been added, all in the same vein.
452 >'s new features include:</P
459 > Can keep outgoing connections alive and reuse them later on.
464 > Supports tagging which allows to change the behaviour
465 based on client and server headers.
470 > Can be run as an "intercepting" proxy, which obviates the need to
471 configure browsers individually.
476 > Sophisticated actions and filters for manipulating both server and client
482 > Can be chained with other proxies.
487 > Integrated browser based configuration and control utility at <A
488 HREF="http://config.privoxy.org/"
490 >http://config.privoxy.org/</A
497 tracing of rule and filter effects. Remote toggling.
502 > Web page filtering (text replacements, removes banners based on size,
506 >, JavaScript and HTML annoyances,
507 pop-up windows, etc.)
512 > Modularized configuration that allows for standard settings and
513 user settings to reside in separate files, so that installing updated
514 actions files won't overwrite individual user settings.
519 > Support for Perl Compatible Regular Expressions in the configuration files, and
520 a more sophisticated and flexible configuration syntax.
525 > Improved cookie management features (e.g. session based cookies).
535 > Bypass many click-tracking scripts (avoids script redirection).
540 > Multi-threaded (POSIX and native threads).
545 > User-customizable HTML templates for most proxy-generated pages (e.g. "blocked" page).
550 > Auto-detection and re-reading of config file changes.
555 > Improved signal handling, and a true daemon mode (Unix).
560 > Every feature now controllable on a per-site or per-location basis, configuration
561 more powerful and versatile over-all.
566 > Many smaller new features added, limitations and bugs removed.
578 >1.8. How does Privoxy know what is
579 an ad, and what is not?</A
585 >'s approach to blocking ads is twofold:</P
587 > First, there are certain patterns in the <SPAN
594 of banner images. This applies to both the path (you wouldn't guess how many
595 web sites serve their banners from a directory called <SPAN
599 and the host (blocking the big banner hosting services like doublecklick.net
600 already helps a lot). <SPAN
603 > takes advantage of this
605 HREF="../user-manual/actions-file.html#AF-PATTERNS"
609 > to sort out and block the requests for things that sound
610 like they would be ads or banners.</P
612 > Second, banners tend to come in certain <SPAN
619 can't tell the size of an image by its URL without downloading it, and if you
620 do, it's too late to save bandwidth. Therefore, <SPAN
624 also inspects the HTML sources of web pages while they are loaded, and replaces
625 references to images with standard banner sizes by dummy references, so that
626 your browser doesn't request them anymore in the first place.</P
628 > Both of this involves a certain amount of guesswork and is, of course, freely
629 and readily configurable.</P
637 >1.9. Can Privoxy make mistakes?
638 This does not sound very scientific.</A
641 > Actually, it's a black art ;-) And yes, it is always possible to have a broad
642 rule accidentally block or change something by mistake. You will almost surely
643 run into such situations at some point. It is tricky writing rules to
644 cover every conceivable possibility, and not occasionally get false positives.</P
646 > But this should not be a big concern since the
650 > configuration is very flexible, and
651 includes tools to help identify these types of situations so they can be
652 addressed as needed, allowing you to customize your installation.
654 HREF="trouble.html#BADSITE"
655 >See the Troubleshooting section below</A
664 >1.10. Will I have to configure Privoxy
665 before I can use it?</A
668 > That depends on your expectations.
669 The default installation should give you a good starting
670 point, and block <SPAN
676 > ads and unwanted content,
677 but many of the more advanced features are off by default, and require
678 you to activate them. </P
680 > You do have to set up your browser to use
685 HREF="installation.html#FIRSTSTEP"
686 >Installation section below</A
689 > And you will certainly run into situations where there are false positives,
690 or ads not being blocked that you may not want to see. In these cases, you
691 would certainly benefit by customizing <SPAN
695 configuration to more closely match your individual situation. And we
696 encourage you to do this. This is where the real power of
708 >1.11. Can Privoxy run as a server on a network?</A
715 > runs as a server already, and can easily be configured to
719 > more than one client. See <A
720 HREF="configuration.html#LANCONFIG"
721 > How can I set up Privoxy to act as a proxy for my LAN</A
730 >1.12. My browser does the same things as
731 Privoxy. Why should I use Privoxy at all?</A
734 > Modern browsers do indeed have <SPAN
741 functionality as <SPAN
745 adequate for you. But <SPAN
749 versatile and powerful, and can probably do a number of things
750 your browser just can't.
753 > In addition, a proxy is good choice if you use multiple browsers, or
754 have a LAN with multiple computers since <SPAN
757 > can run as a server
758 application. This way all the configuration is in one place, and you don't
759 have to maintain a similar configuration for possibly many browsers or
763 > Note, however, that it's recommended to leverage both your browser's
767 > privacy enhancing features
768 at the same time. While your browser probably lacks some features
772 > offers, it should also be able to do some things more
773 reliable, for example restricting and suppressing JavaScript.
782 >1.13. Why should I trust Privoxy?</A
785 > The most important reason is because you have access to
792 >, and you can control everything. You can
793 check every line of every configuration file yourself. You can check every
794 last bit of source code should you desire. And even if you can't read code,
795 there should be some comfort in knowing that other people can,
796 and do read it. You can build the software from scratch, if you want,
797 so that you know the executable is clean, and that it is
804 >. In fact, we encourage this level of scrutiny. It
805 is one reason we use <SPAN
817 >1.14. Is there is a license or fee? What about a
818 warranty? Registration?</A
824 > is free software and licensed under the <A
825 HREF="http://www.gnu.org/licenses/old-licenses/gpl-2.0.html"
827 >GNU General Public License (GPL) version 2</A
829 It is free to use, copy, modify or distribute as you wish under the terms of this
830 license. Please see the <A
831 HREF="copyright.html"
834 information on the license and copyright. Or the <TT
838 that should be included.
847 > of any kind, expressed, implied or otherwise.
848 That is something that would cost real money ;-) There is no registration either.
857 >1.15. Can Privoxy remove spyware? Adware? Viruses?</A
860 > No, at least not reliably enough to trust it. <SPAN
863 > is not designed to be
864 a malware removal tool and the default configuration doesn't even try to
865 filter out any malware.</P
870 > could help prevent contact from (known) sites that use such
871 tactics with appropriate configuration rules, and thus could conceivably
872 prevent contamination from such sites. However, keeping such a configuration
873 up to date would require a lot of time and effort that would be better spend
874 on keeping your software itself up to date so it doesn't have known
883 >1.16. Can I use Privoxy with other ad-blocking software?</A
889 > should work fine with other proxies and other software in general.</P
891 > But it is probably not necessary to use <SPAN
894 > in conjunction with other
895 ad-blocking products, and this could conceivably cause undesirable results.
896 It might be better to choose one software or the other and work a little to
897 tweak its configuration to your liking.</P
899 > Note that this is an advice specific to ad blocking.</P
907 >1.17. I would like to help you, what can I do?</A
915 >1.17.1. Would you like to participate?</A
924 > need help. There is something for
925 everybody who wants to help us. We welcome new developers, packagers,
926 testers, documentation writers or really anyone with a desire to help in
937 >. There are many other tasks available. In fact,
938 the programmers often can't spend as much time programming because of some
939 of the other, more mundane things that need to be done, like checking the
940 Tracker feedback sections.
944 HREF="https://sourceforge.net/account/register.php"
946 >get an account on SourceForge.net</A
948 and mail your id to the <A
949 HREF="mailto:ijbswa-developers@lists.sourceforge.net"
953 >. Then, please read the <A
954 HREF="../developer-manual/index.html"
956 >Developer's Manual</A
958 the pertinent sections.</P
960 > You can also start helping out without SourceForge.net account,
961 simply by showing up on the mailing list, helping out other users,
962 providing general feedback or reporting problems you noticed.
970 NAME="JOINTEAM-MONEY"
971 >1.17.2. Contribute!</A
974 > We, of course, welcome donations and could use money for domain registering,
975 buying software to test <SPAN
978 > with, and, of course,
979 for regular world-wide get-togethers (hahaha). If you enjoy the software and feel
980 like helping us with a donation, just <A
981 HREF="mailto: ijbswa-developers@lists.sourceforge.net"
985 and get your name on the list of contributors.</P
992 NAME="JOINTEAM-SOFTWARE"
996 > If you are a vendor of a web-related software like a browser, web server
997 or proxy, and would like us to ensure that <SPAN
1001 runs smoothly with your product, you might consider supplying us with a
1002 copy or license. We can't, however, guarantee that we will fix all potential
1003 compatibility issues as a result.</P
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