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40 >Privoxy Frequently Asked Questions</TH
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77 >1. General Information</A
85 >1.1. Who should give <SPAN
91 > Anyone who is interested in security, privacy, or in
92 finer-grained control over their web and Internet experience.
101 >1.2. Is Privoxy the best choice for
108 > is certainly a good choice, especially for those who want more
109 control and security. Those with the willingness to read the documentation
110 and the ability to fine-tune their installation will benefit the most.
117 strengths is that it is highly configurable giving you the ability to
118 completely personalize your installation. Being familiar with, or at least
119 having an interest in learning about <A
120 HREF="http://en.wikipedia.org/wiki/Http"
123 > and other networking
125 HREF="http://en.wikipedia.org/wiki/Html"
130 HREF="http://en.wikipedia.org/wiki/Regular_expressions"
138 will be a big plus and will help you get the most out of <SPAN
142 A new installation just includes a very basic configuration. The user
143 should take this as a starting point only, and enhance it as he or she
144 sees fit. In fact, the user is encouraged, and expected to, fine-tune the
151 > configuration can be done
153 HREF="http://en.wikipedia.org/wiki/Web_browser"
157 But there are areas where configuration is done using a
159 HREF="http://en.wikipedia.org/wiki/Text_editors"
163 to edit configuration files. Also note that the web-based action editor
164 doesn't use authentication and should only be enabled in environments
165 where all clients with access to <SPAN
168 > listening port can be trusted.
177 >1.3. What is a <SPAN
185 HREF="http://en.wikipedia.org/wiki/Proxy_server"
189 is a service, based on a software such as
193 >, that clients (i.e. browsers) can use
194 instead of connecting directly to web servers on the Internet. The
195 clients then ask the proxy to fetch the objects they need (web pages,
196 images, movies etc) on their behalf, and when the proxy has done so, it
197 hands the results back to the client. It is a <SPAN
202 HREF="http://en.wikipedia.org/wiki/Proxy_server"
209 > There are many reasons to use web proxies, such as security (firewalling),
210 efficiency (caching) and others, and there are any number of proxies
211 to accommodate those needs.
217 > is a proxy that is primarily focused on privacy
218 protection, ad and junk elimination and freeing the user from restrictions placed on his
219 activities. Sitting between your browser(s) and the Internet,
220 it is in a perfect position to filter outbound personal information that your
221 browser is leaking, as well as inbound junk. It uses a variety of techniques to do
222 this, all of which are under your complete control via the various configuration
223 files and options. Being a proxy also makes it easier to share
224 configurations among multiple browsers and/or users.
233 >1.4. Does Privoxy do anything more than ad blocking?</A
237 Yes, ad blocking is but one possible use. There are many, many ways <SPAN
241 can be used to sanitize and customize web browsing. </P
249 >1.5. What is this new version of
256 > A long time ago, there was the
258 HREF="http://www.junkbusters.com/ijb.html"
262 >Internet Junkbuster</SPAN
265 by Anonymous Coders and <A
266 HREF="http://www.junkbusters.com/"
270 >. This saved many users a lot of pain in the early days of
271 web advertising and user tracking.</P
273 > But the web, its protocols and standards, and with it, the techniques for
274 forcing ads on users, give up autonomy over their browsing, and
275 for tracking them, keeps evolving. Unfortunately, the <SPAN
279 > did not. Version 2.0.2, published in 1998, was
280 (and is) the last official
282 HREF="http://www.junkbusters.com/ijbdist.html#release"
287 HREF="http://www.junkbusters.com"
289 >Junkbusters Corporation</A
291 Fortunately, it had been released under the GNU
293 HREF="http://www.gnu.org/licenses/gpl.html"
296 >, which allowed further
297 development by others.</P
299 > So Stefan Waldherr started maintaining an
301 HREF="http://www.waldherr.org/junkbuster/"
303 >improved version of the
305 >, to which eventually a number of people contributed patches.
306 It could already replace banners with a transparent image, and had a first
307 version of pop-up killing, but it was still very closely based on the
308 original, with all its limitations, such as the lack of HTTP/1.1 support,
309 flexible per-site configuration, or content modification. The last release
310 from this effort was version 2.0.2-10, published in 2000.</P
314 HREF="http://www.privoxy.org/user-manual/copyright.html#AUTHORS"
318 picked up the thread, and started turning the software inside out, upside down,
319 and then reassembled it, adding many
321 HREF="http://www.privoxy.org/user-manual/introduction.html#FEATURES"
327 > The result of this is <SPAN
331 stable version, 3.0, was released August, 2002.
343 >? Why change the name from
344 Junkbuster at all?</A
347 > Though outdated, <A
348 HREF="http://junkbusters.com/"
350 >Junkbusters Corporation</A
352 continues to offer their original version of the <SPAN
360 >-derived software under the same name
363 > There are also potential legal complications from our use of the
367 > name, which is a registered trademark of
369 HREF="http://junkbusters.com/"
371 >Junkbusters Corporation</A
373 There are, however, no objections from Junkbusters Corporation to the
377 > project itself, and they, in fact, still
378 share our ideals and goals.</P
380 > The developers also believed that there are so many improvements over the original
381 code, that it was time to make a clean break from the past and make
382 a name in their own right.</P
394 >Privacy Enhancing Proxy</I
398 modification and junk suppression gives <SPAN
405 control, more freedom, and allows you to browse your personal and
423 >1.7. How does Privoxy differ
424 from the old Junkbuster?</A
434 > left off. All the old features remain.
438 > still blocks ads and banners,
440 HREF="http://en.wikipedia.org/wiki/Browser_cookie"
444 helps protect your privacy. But, most of these features have been enhanced,
445 and many new ones have been added, all in the same vein.
451 >'s new features include:</P
458 > Can be run as an "intercepting" proxy, which obviates the need to
459 configure browsers individually.
464 > Sophisticated actions and filters for manipulating both server and client
470 > Can be chained with other proxies.
475 > Integrated browser based configuration and control utility at <A
476 HREF="http://config.privoxy.org/"
478 >http://config.privoxy.org/</A
485 tracing of rule and filter effects. Remote toggling.
490 > Web page filtering (text replacements, removes banners based on size,
494 >, JavaScript and HTML annoyances,
495 pop-up windows, etc.)
500 > Modularized configuration that allows for standard settings and
501 user settings to reside in separate files, so that installing updated
502 actions files won't overwrite individual user settings.
507 > Support for Perl Compatible Regular Expressions in the configuration files, and
508 a more sophisticated and flexible configuration syntax.
513 > Improved cookie management features (e.g. session based cookies).
523 > Bypass many click-tracking scripts (avoids script redirection).
528 > Multi-threaded (POSIX and native threads).
533 > User-customizable HTML templates for all proxy-generated pages (e.g. "blocked" page).
538 > Auto-detection and re-reading of config file changes.
543 > Improved signal handling, and a true daemon mode (Unix).
548 > Every feature now controllable on a per-site or per-location basis, configuration
549 more powerful and versatile over-all.
554 > Many smaller new features added, limitations and bugs removed, and security holes fixed.
566 >1.8. How does Privoxy know what is
567 an ad, and what is not?</A
573 >'s approach to blocking ads is twofold:</P
575 > First, there are certain patterns in the <SPAN
582 of banner images. This applies to both the path (you wouldn't guess how many
583 web sites serve their banners from a directory called <SPAN
587 and the host (blocking the big banner hosting services like doublecklick.net
588 already helps a lot). <SPAN
591 > takes advantage of this
593 HREF="../user-manual/actions-file.html#AF-PATTERNS"
597 > to sort out and block the requests for things that sound
598 like they would be ads or banners.</P
600 > Second, banners tend to come in certain <SPAN
607 can't tell the size of an image by its URL without downloading it, and if you
608 do, it's too late to save bandwidth. Therefore, <SPAN
612 also inspects the HTML sources of web pages while they are loaded, and replaces
613 references to images with standard banner sizes by dummy references, so that
614 your browser doesn't request them anymore in the first place.</P
616 > Both of this involves a certain amount of guesswork and is, of course, freely
617 and readily configurable.</P
625 >1.9. Can Privoxy make mistakes?
626 This does not sound very scientific.</A
629 > Actually, it's a black art ;-) And yes, it is always possible to have a broad
630 rule accidentally block or change something by mistake. You will almost surely
631 run into such situations at some point. It is tricky writing rules to
632 cover every conceivable possibility, and not occasionally get false positives.</P
634 > But this should not be a big concern since the
638 > configuration is very flexible, and
639 includes tools to help identify these types of situations so they can be
640 addressed as needed, allowing you to customize your installation.
642 HREF="trouble.html#BADSITE"
643 >See the Troubleshooting section below</A
652 >1.10. Will I have to configure Privoxy
653 before I can use it?</A
656 > That depends on your expectations.
657 The default installation should give you a good starting
658 point, and block <SPAN
664 > ads and unwanted content,
665 but many of the more advanced features are off by default, and require
666 you to activate them. </P
668 > You do have to set up your browser to use
673 HREF="installation.html#FIRSTSTEP"
674 >Installation section below</A
677 > And you will certainly run into situations where there are false positives,
678 or ads not being blocked that you may not want to see. In these cases, you
679 would certainly benefit by customizing <SPAN
683 configuration to more closely match your individual situation. And we
684 encourage you to do this. This is where the real power of
696 >1.11. Can Privoxy run as a server on a network?</A
703 > runs as a server already, and can easily be configured to
707 > more than one client. See <A
708 HREF="configuration.html#LANCONFIG"
709 > How can I set up Privoxy to act as a proxy for my LAN</A
718 >1.12. My browser does the same things as
719 Privoxy. Why should I use Privoxy at all?</A
722 > Modern browsers do indeed have <SPAN
729 functionality as <SPAN
733 adequate for you. But <SPAN
737 versatile and powerful, and can probably do a number of things
738 your browser just can't.
741 > In addition, a proxy is good choice if you use multiple browsers, or
742 have a LAN with multiple computers since <SPAN
745 > can run as a server
746 application. This way all the configuration is in one place, and you don't
747 have to maintain a similar configuration for possibly many browsers or
751 > Note, however, that it's recommended to leverage both your browser's
755 > privacy enhancing features
756 at the same time. While your browser probably lacks some features
760 > offers, it should also be able to do some things more
761 reliable, for example restricting and suppressing JavaScript.
770 >1.13. Why should I trust Privoxy?</A
773 > The most important reason is because you have access to
780 >, and you can control everything. You can
781 check every line of every configuration file yourself. You can check every
782 last bit of source code should you desire. And even if you can't read code,
783 there should be some comfort in knowing that other people can,
784 and do read it. You can build the software from scratch, if you want,
785 so that you know the executable is clean, and that it is
792 >. In fact, we encourage this level of scrutiny. It
793 is one reason we use <SPAN
805 >1.14. Is there is a license or fee? What about a
806 warranty? Registration?</A
812 > is free software and licensed under the <A
813 HREF="http://www.gnu.org/licenses/old-licenses/gpl-2.0.html"
815 >GNU General Public License (GPL) version 2</A
817 It is free to use, copy, modify or distribute as you wish under the terms of this
818 license. Please see the <A
819 HREF="copyright.html"
822 information on the license and copyright. Or the <TT
826 that should be included.
835 > of any kind, expressed, implied or otherwise.
836 That is something that would cost real money ;-) There is no registration either.
845 >1.15. Can Privoxy remove spyware? Adware? Viruses?</A
848 > No, at least not reliably enough to trust it. <SPAN
851 > is not designed to be
852 a malware removal tool and the default configuration doesn't even try to
853 filter out any malware.</P
858 > could help prevent contact from (known) sites that use such
859 tactics with appropriate configuration rules, and thus could conceivably
860 prevent contamination from such sites. However, keeping such a configuration
861 up to date would require a lot of time and effort that would be better spend
862 on keeping your software itself up to date so it doesn't have known
871 >1.16. Can I use Privoxy with other ad-blocking software?</A
877 > should work fine with other proxies and other software in general.</P
879 > But it is probably not necessary to use <SPAN
882 > in conjunction with other
883 ad-blocking products, and this could conceivably cause undesirable results.
884 It might be better to choose one software or the other and work a little to
885 tweak its configuration to your liking.</P
887 > Note that this is an advice specific to ad blocking.</P
895 >1.17. I would like to help you, what can I do?</A
903 >1.17.1. Would you like to participate?</A
912 > need help. There is something for
913 everybody who wants to help us. We welcome new developers, packagers,
914 testers, documentation writers or really anyone with a desire to help in
925 >. There are many other tasks available. In fact,
926 the programmers often can't spend as much time programming because of some
927 of the other, more mundane things that need to be done, like checking the
928 Tracker feedback sections.
932 HREF="https://sourceforge.net/account/register.php"
934 >get an account on SourceForge.net</A
936 and mail your id to the <A
937 HREF="mailto:ijbswa-developers@lists.sourceforge.net"
941 >. Then, please read the <A
942 HREF="../developer-manual/index.html"
944 >Developer's Manual</A
946 the pertinent sections.</P
948 > You can also start helping out without SourceForge.net account,
949 simply by showing up on the mailing list, helping out other users,
950 providing general feedback or reporting problems you noticed.
958 NAME="JOINTEAM-MONEY"
959 >1.17.2. Contribute!</A
962 > We, of course, welcome donations and could use money for domain registering,
963 buying software to test <SPAN
966 > with, and, of course,
967 for regular world-wide get-togethers (hahaha). If you enjoy the software and feel
968 like helping us with a donation, just <A
969 HREF="mailto: ijbswa-developers@lists.sourceforge.net"
973 and get your name on the list of contributors.</P
980 NAME="JOINTEAM-SOFTWARE"
984 > If you are a vendor of a web-related software like a browser, web server
985 or proxy, and would like us to ensure that <SPAN
989 runs smoothly with your product, you might consider supplying us with a
990 copy or license. We can't, however, guarantee that we will fix all potential
991 compatibility issues as a result.</P
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