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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/old-licenses/gpl-2.0.html"
298 which allowed further development by others.</P
300 > So Stefan Waldherr started maintaining an improved version of the
301 software, to which eventually a number of people contributed patches.
302 It could already replace banners with a transparent image, and had a first
303 version of pop-up killing, but it was still very closely based on the
304 original, with all its limitations, such as the lack of HTTP/1.1 support,
305 flexible per-site configuration, or content modification. The last release
306 from this effort was version 2.0.2-10, published in 2000.</P
310 HREF="http://www.privoxy.org/user-manual/copyright.html#AUTHORS"
314 picked up the thread, and started turning the software inside out, upside down,
315 and then reassembled it, adding many
317 HREF="http://www.privoxy.org/user-manual/introduction.html#FEATURES"
323 > The result of this is <SPAN
327 stable version, 3.0, was released August, 2002.
339 >? Why change the name from
340 Junkbuster at all?</A
343 > Though outdated, <A
344 HREF="http://junkbusters.com/"
346 >Junkbusters Corporation</A
348 continues to offer their original version of the <SPAN
356 >-derived software under the same name
359 > There are also potential legal complications from our use of the
363 > name, which is a registered trademark of
365 HREF="http://junkbusters.com/"
367 >Junkbusters Corporation</A
369 There are, however, no objections from Junkbusters Corporation to the
373 > project itself, and they, in fact, still
374 share our ideals and goals.</P
376 > The developers also believed that there are so many improvements over the original
377 code, that it was time to make a clean break from the past and make
378 a name in their own right.</P
390 >Privacy Enhancing Proxy</I
394 modification and junk suppression gives <SPAN
401 control, more freedom, and allows you to browse your personal and
419 >1.7. How does Privoxy differ
420 from the old Junkbuster?</A
434 > still blocks ads and banners,
436 HREF="http://en.wikipedia.org/wiki/Browser_cookie"
440 helps protect your privacy. But, most of these features have been enhanced,
441 and many new ones have been added, all in the same vein.
447 >'s new features include:</P
454 > Can keep outgoing connections alive and reuse them later on.
459 > Supports tagging which allows to change the behaviour
460 based on client and server headers.
465 > Can be run as an "intercepting" proxy, which obviates the need to
466 configure browsers individually.
471 > Sophisticated actions and filters for manipulating both server and client
477 > Can be chained with other proxies.
482 > Integrated browser based configuration and control utility at <A
483 HREF="http://config.privoxy.org/"
485 >http://config.privoxy.org/</A
492 tracing of rule and filter effects. Remote toggling.
497 > Web page filtering (text replacements, removes banners based on size,
501 >, JavaScript and HTML annoyances,
502 pop-up windows, etc.)
507 > Modularized configuration that allows for standard settings and
508 user settings to reside in separate files, so that installing updated
509 actions files won't overwrite individual user settings.
514 > Support for Perl Compatible Regular Expressions in the configuration files, and
515 a more sophisticated and flexible configuration syntax.
520 > Improved cookie management features (e.g. session based cookies).
530 > Bypass many click-tracking scripts (avoids script redirection).
535 > Multi-threaded (POSIX and native threads).
540 > User-customizable HTML templates for most proxy-generated pages (e.g. "blocked" page).
545 > Auto-detection and re-reading of config file changes.
550 > Improved signal handling, and a true daemon mode (Unix).
555 > Every feature now controllable on a per-site or per-location basis, configuration
556 more powerful and versatile over-all.
561 > Many smaller new features added, limitations and bugs removed.
573 >1.8. How does Privoxy know what is
574 an ad, and what is not?</A
580 >'s approach to blocking ads is twofold:</P
582 > First, there are certain patterns in the <SPAN
589 of banner images. This applies to both the path (you wouldn't guess how many
590 web sites serve their banners from a directory called <SPAN
594 and the host (blocking the big banner hosting services like doublecklick.net
595 already helps a lot). <SPAN
598 > takes advantage of this
600 HREF="../user-manual/actions-file.html#AF-PATTERNS"
604 > to sort out and block the requests for things that sound
605 like they would be ads or banners.</P
607 > Second, banners tend to come in certain <SPAN
614 can't tell the size of an image by its URL without downloading it, and if you
615 do, it's too late to save bandwidth. Therefore, <SPAN
619 also inspects the HTML sources of web pages while they are loaded, and replaces
620 references to images with standard banner sizes by dummy references, so that
621 your browser doesn't request them anymore in the first place.</P
623 > Both of this involves a certain amount of guesswork and is, of course, freely
624 and readily configurable.</P
632 >1.9. Can Privoxy make mistakes?
633 This does not sound very scientific.</A
636 > Actually, it's a black art ;-) And yes, it is always possible to have a broad
637 rule accidentally block or change something by mistake. You will almost surely
638 run into such situations at some point. It is tricky writing rules to
639 cover every conceivable possibility, and not occasionally get false positives.</P
641 > But this should not be a big concern since the
645 > configuration is very flexible, and
646 includes tools to help identify these types of situations so they can be
647 addressed as needed, allowing you to customize your installation.
649 HREF="trouble.html#BADSITE"
650 >See the Troubleshooting section below</A
659 >1.10. Will I have to configure Privoxy
660 before I can use it?</A
663 > That depends on your expectations.
664 The default installation should give you a good starting
665 point, and block <SPAN
671 > ads and unwanted content,
672 but many of the more advanced features are off by default, and require
673 you to activate them. </P
675 > You do have to set up your browser to use
680 HREF="installation.html#FIRSTSTEP"
681 >Installation section below</A
684 > And you will certainly run into situations where there are false positives,
685 or ads not being blocked that you may not want to see. In these cases, you
686 would certainly benefit by customizing <SPAN
690 configuration to more closely match your individual situation. And we
691 encourage you to do this. This is where the real power of
703 >1.11. Can Privoxy run as a server on a network?</A
710 > runs as a server already, and can easily be configured to
714 > more than one client. See <A
715 HREF="configuration.html#LANCONFIG"
716 > How can I set up Privoxy to act as a proxy for my LAN</A
725 >1.12. My browser does the same things as
726 Privoxy. Why should I use Privoxy at all?</A
729 > Modern browsers do indeed have <SPAN
736 functionality as <SPAN
740 adequate for you. But <SPAN
744 versatile and powerful, and can probably do a number of things
745 your browser just can't.
748 > In addition, a proxy is good choice if you use multiple browsers, or
749 have a LAN with multiple computers since <SPAN
752 > can run as a server
753 application. This way all the configuration is in one place, and you don't
754 have to maintain a similar configuration for possibly many browsers or
758 > Note, however, that it's recommended to leverage both your browser's
762 > privacy enhancing features
763 at the same time. While your browser probably lacks some features
767 > offers, it should also be able to do some things more
768 reliable, for example restricting and suppressing JavaScript.
777 >1.13. Why should I trust Privoxy?</A
780 > The most important reason is because you have access to
787 >, and you can control everything. You can
788 check every line of every configuration file yourself. You can check every
789 last bit of source code should you desire. And even if you can't read code,
790 there should be some comfort in knowing that other people can,
791 and do read it. You can build the software from scratch, if you want,
792 so that you know the executable is clean, and that it is
799 >. In fact, we encourage this level of scrutiny. It
800 is one reason we use <SPAN
812 >1.14. Is there is a license or fee? What about a
813 warranty? Registration?</A
819 > is free software and licensed under the <A
820 HREF="http://www.gnu.org/licenses/old-licenses/gpl-2.0.html"
822 >GNU General Public License (GPL) version 2</A
824 It is free to use, copy, modify or distribute as you wish under the terms of this
825 license. Please see the <A
826 HREF="copyright.html"
829 information on the license and copyright. Or the <TT
833 that should be included.
842 > of any kind, expressed, implied or otherwise.
843 That is something that would cost real money ;-) There is no registration either.
852 >1.15. Can Privoxy remove spyware? Adware? Viruses?</A
855 > No, at least not reliably enough to trust it. <SPAN
858 > is not designed to be
859 a malware removal tool and the default configuration doesn't even try to
860 filter out any malware.</P
865 > could help prevent contact from (known) sites that use such
866 tactics with appropriate configuration rules, and thus could conceivably
867 prevent contamination from such sites. However, keeping such a configuration
868 up to date would require a lot of time and effort that would be better spend
869 on keeping your software itself up to date so it doesn't have known
878 >1.16. Can I use Privoxy with other ad-blocking software?</A
884 > should work fine with other proxies and other software in general.</P
886 > But it is probably not necessary to use <SPAN
889 > in conjunction with other
890 ad-blocking products, and this could conceivably cause undesirable results.
891 It might be better to choose one software or the other and work a little to
892 tweak its configuration to your liking.</P
894 > Note that this is an advice specific to ad blocking.</P
901 NAME="HELP-THE-DEVELOPERS"
902 >1.17. I would like to help you, what can I do?</A
910 >1.17.1. Would you like to participate?</A
919 > need help. There is something for
920 everybody who wants to help us. We welcome new developers, packagers,
921 testers, documentation writers or really anyone with a desire to help in
932 >. There are many other tasks available. In fact,
933 the programmers often can't spend as much time programming because of some
934 of the other, more mundane things that need to be done, like checking the
935 Tracker feedback sections or responding to user questions on the mailing
939 > So first thing, subscribe to the <A
940 HREF="https://lists.sourceforge.net/lists/listinfo/ijbswa-users"
945 HREF="https://lists.sourceforge.net/lists/listinfo/ijbswa-developers"
949 > mailing list, join the discussion, help out other users, provide general
950 feedback or report problems you noticed.
953 > If you intend to help out with the trackers, you also might want to <A
954 HREF="https://sourceforge.net/account/register.php"
956 >get an account on SourceForge.net</A
958 so we don't confuse you with the other name-less users.
962 HREF="../developer-manual/index.html"
964 >Developer's Manual</A
966 While it is partly out of date, it's still worth reading.</P
974 >1.17.2. Would you like to donate?</A
980 > is developed by unpaid volunteers
981 and thus our current running costs are pretty low. Nevertheless, we
982 have plans that will cost money in the future. We would like to get
983 this money through donations made by our users.</P
988 > has therefore become an associated
990 HREF="http://www.spi-inc.org/about-spi/about-spi"
993 in the Public Interest (SPI)</A
994 >, which allows us to receive tax-deductible
995 donations in most western countries.</P
997 > We intend to use the donations to pay for our domain after transfering
998 it to SPI. Our goal is to make sure there's no single point of failure
999 and the bill gets paid and the site keeps running even if a some of
1000 the currently active developers were to suddenly disappear for a while.</P
1002 > We would also like to spend some money on more reliable hosting,
1003 on hardware to help make sure <SPAN
1007 keeps running on platforms the developers currently can't test on,
1008 and on technical books to educate our developers about said platforms
1009 or to improve their knowledge in general.</P
1011 > If you enjoy our software and feel like helping out with a donation,
1012 please have a look at
1014 HREF="http://www.spi-inc.org/donations"
1016 >SPI's donation page</A
1018 to see what the options are.</P
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