1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01
2 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
5 <meta name="generator" content="HTML Tidy, see www.w3.org">
9 <meta name="GENERATOR" content=
10 "Modular DocBook HTML Stylesheet Version 1.79">
11 <link rel="HOME" title="Privoxy Frequently Asked Questions" href=
13 <link rel="PREVIOUS" title="Configuration" href="configuration.html">
14 <link rel="NEXT" title="Troubleshooting" href="trouble.html">
15 <link rel="STYLESHEET" type="text/css" href="../p_doc.css">
16 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
17 <style type="text/css">
19 background-color: #EEEEEE;
22 :link { color: #0000FF }
23 :visited { color: #840084 }
24 :active { color: #0000FF }
25 hr.c1 {text-align: left}
29 <div class="NAVHEADER">
30 <table summary="Header navigation table" width="100%" border="0"
31 cellpadding="0" cellspacing="0">
33 <th colspan="3" align="center">
34 Privoxy Frequently Asked Questions
38 <td width="10%" align="left" valign="bottom">
39 <a href="configuration.html" accesskey="P">Prev</a>
41 <td width="80%" align="center" valign="bottom">
43 <td width="10%" align="right" valign="bottom">
44 <a href="trouble.html" accesskey="N">Next</a>
48 <hr width="100%" class="c1">
52 <a name="MISC">4. Miscellaneous</a>
56 <a name="AEN729">4.1. How much does Privoxy slow my browsing down?
57 This has to add extra time to browsing.</a>
60 How much of an impact depends on many things, including the CPU of
61 the host system, how aggressive the configuration is, which
62 specific actions are being triggered, the size of the page, the
63 bandwidth of the connection, etc.
66 Overall, it should not slow you down any in real terms, and may
67 actually help speed things up since ads, banners and other junk are
68 not typically being retrieved and displayed. The actual processing
69 time required by <span class="APPLICATION">Privoxy</span> itself
70 for each page, is relatively small in the overall scheme of things,
71 and happens very quickly. This is typically more than offset by
72 time saved not downloading and rendering ad images and other junk
73 content (if ad blocking is being used).
76 <span class="QUOTE">"Filtering"</span> content via the <tt class=
77 "LITERAL"><a href="../user-manual/actions-file.html#FILTER" target=
78 "_top">filter</a></tt> or <tt class="LITERAL"><a href=
79 "../user-manual/actions-file.html#DEANIMATE-GIFS" target=
80 "_top">deanimate-gifs</a></tt> actions may cause a perceived
81 slowdown, since the entire document needs to be buffered before
82 displaying. And on very large documents, filtering may have some
83 measurable impact. How much depends on the page size, the actual
84 definition of the filter(s), etc. See below. Most other actions
85 have little to no impact on speed.
88 Also, when filtering is enabled but zlib support isn't available,
89 compression is often disabled (see <a href=
90 "../user-manual/actions-file.html#PREVENT-COMPRESSION" target=
91 "_top">prevent-compression</a>). This can have an impact on speed
92 as well, although it's probably smaller than you might think.
93 Again, the page size, etc. will determine how much of an impact.
98 <a name="LOADINGTIMES">4.2. I notice considerable delays in page
99 requests. What's wrong?</a>
102 If you use any <tt class="LITERAL"><a href=
103 "../user-manual/actions-file.html#FILTER" target=
104 "_top">filter</a></tt> action, such as filtering banners by size,
105 web-bugs etc, or the <tt class="LITERAL"><a href=
106 "../user-manual/actions-file.html#DEANIMATE-GIFS" target=
107 "_top">deanimate-gifs</a></tt> action, the entire document must be
108 loaded into memory in order for the filtering mechanism to work,
109 and nothing is sent to the browser during this time.
112 The loading time typically does not really change much in real
113 numbers, but the feeling is different, because most browsers are
114 able to start rendering incomplete content, giving the user a
115 feeling of "it works". This effect is more noticeable on slower
116 dialup connections. Extremely large documents may have some impact
117 on the time to load the page where there is filtering being done.
118 But overall, the difference should be very minimal. If there is a
119 big impact, then probably some other situation is contributing
120 (like anti-virus software).
123 Filtering is automatically disabled for inappropriate MIME types.
124 But note that if the web server mis-reports the MIME type, then
125 content that should not be filtered, could be. <span class=
126 "APPLICATION">Privoxy</span> only knows how to differentiate
127 filterable content because of the MIME type as reported by the
128 server, or because of some configuration setting that
129 enables/disables filtering.
134 <a name="CONFIGURL">4.3. What are "http://config.privoxy.org/" and
138 <a href="http://config.privoxy.org/" target=
139 "_top">http://config.privoxy.org/</a> is the address of <span
140 class="APPLICATION">Privoxy</span>'s built-in user interface, and
141 <a href="http://p.p/" target="_top">http://p.p/</a> is a shortcut
145 Since <span class="APPLICATION">Privoxy</span> sits between your
146 web browser and the Internet, it can simply intercept requests for
147 these addresses and answer them with its built-in <span class=
148 "QUOTE">"web server"</span>.
151 This also makes for a good test for your browser configuration: If
152 entering the URL <a href="http://config.privoxy.org/" target=
153 "_top">http://config.privoxy.org/</a> takes you to a page saying
154 <span class="QUOTE">"This is Privoxy ..."</span>, everything is OK.
155 If you get a page saying <span class="QUOTE">"Privoxy is not
156 working"</span> instead, then your browser didn't use <span class=
157 "APPLICATION">Privoxy</span> for the request, hence it could not be
158 intercepted, and you have accessed the <span class="emphasis"><i
159 class="EMPHASIS">real</i></span> web site at config.privoxy.org.
164 <a name="NEWADS">4.4. How can I submit new ads, or report
168 Please see the <a href="contact.html">Contact section</a> for
169 various ways to interact with the developers.
174 <a name="NEWADS2">4.5. If I do submit missed ads, will they be
175 included in future updates?</a>
178 Whether such submissions are eventually included in the <tt class=
179 "FILENAME">default.action</tt> configuration file depends on how
180 significant the issue is. We of course want to address any
181 potential problem with major, high-profile sites such as <i class=
182 "CITETITLE">Google</i>, <i class="CITETITLE">Yahoo</i>, etc. Any
183 site with global or regional reach, has a good chance of being a
184 candidate. But at the other end of the spectrum are any number of
185 smaller, low-profile sites such as for local clubs or schools.
186 Since their reach and impact are much less, they are best handled
187 by inclusion in the user's <tt class="FILENAME">user.action</tt>,
188 and thus would be unlikely to be included.
193 <a name="NOONECARES">4.6. Why doesn't anyone answer my support
197 Rest assured that it has been read and considered. Why it is not
198 answered, could be for various reasons, including no one has a good
199 answer for it, no one has had time to yet investigate it
200 thoroughly, it has been reported numerous times already, or because
201 not enough information was provided to help us help you. Your
202 efforts are not wasted, and we do appreciate them.
207 <a name="IP">4.7. How can I hide my IP address?</a>
210 If you run both the browser and <span class=
211 "APPLICATION">Privoxy</span> locally, you cannot hide your IP
212 address with <span class="APPLICATION">Privoxy</span> or ultimately
213 any other software alone. The server needs to know your IP address
214 so that it knows where to send the responses back.
217 There are many publicly usable "anonymous" proxies out there, which
218 provide a further level of indirection between you and the web
222 However, these proxies are called "anonymous" because you don't
223 need to authenticate, not because they would offer any real
224 anonymity. Most of them will log your IP address and make it
225 available to the authorities in case you violate the law of the
226 country they run in. In fact you can't even rule out that some of
227 them only exist to *collect* information on (those suspicious)
228 people with a more than average preference for privacy.
231 If you want to hide your IP address from most adversaries, you
232 should consider chaining <span class="APPLICATION">Privoxy</span>
233 with <a href="https://www.torproject.org/" target="_top">Tor</a>.
234 The configuration details can be found in <a href="#TOR" target=
235 "_top">How do I use <span class="APPLICATION">Privoxy</span>
236 together with <span class="APPLICATION">Tor</span> section</a> just
242 <a name="AEN794">4.8. Can Privoxy guarantee I am anonymous?</a>
245 No. Your chances of remaining anonymous are improved, but unless
246 you <a href="#TOR" target="_top">chain <span class=
247 "APPLICATION">Privoxy</span> with <span class=
248 "APPLICATION">Tor</span></a> or a similar proxy and know what
249 you're doing when it comes to configuring the rest of your system,
250 you should assume that everything you do on the Web can be traced
254 <span class="APPLICATION">Privoxy</span> can remove various
255 information about you, and allows <span class="emphasis"><i class=
256 "EMPHASIS">you</i></span> more freedom to decide which sites you
257 can trust, and what details you want to reveal. But it neither
258 hides your IP address, nor can it guarantee that the rest of the
259 system behaves correctly. There are several possibilities how a web
260 sites can find out who you are, even if you are using a strict
261 <span class="APPLICATION">Privoxy</span> configuration and chained
262 it with <span class="APPLICATION">Tor</span>.
265 Most of <span class="APPLICATION">Privoxy's</span>
266 privacy-enhancing features can be easily subverted by an insecure
267 browser configuration, therefore you should use a browser that can
268 be configured to only execute code from trusted sites, and be
269 careful which sites you trust. For example there is no point in
270 having <span class="APPLICATION">Privoxy</span> modify the
271 User-Agent header, if websites can get all the information they
272 want through JavaScript, ActiveX, Flash, Java etc.
275 A few browsers disclose the user's email address in certain
276 situations, such as when transferring a file by FTP. <span class=
277 "APPLICATION">Privoxy</span> does not filter FTP. If you need this
278 feature, or are concerned about the mail handler of your browser
279 disclosing your email address, you might consider products such as
280 <span class="APPLICATION">NSClean</span>.
283 Browsers available only as binaries could use non-standard headers
284 to give out any information they can have access to: see the
285 manufacturer's license agreement. It's impossible to anticipate and
286 prevent every breach of privacy that might occur. The
287 professionally paranoid prefer browsers available as source code,
288 because anticipating their behavior is easier. Trust the source,
294 <a name="AEN812">4.9. A test site says I am not using a Proxy.</a>
297 Good! Actually, they are probably testing for some other kinds of
298 proxies. Hiding yourself completely would require additional steps.
303 <a name="TOR">4.10. How do I use Privoxy together with Tor?</a>
306 Before you configure <span class="APPLICATION">Privoxy</span> to
307 use <a href="https://www.torproject.org/" target="_top">Tor</a>,
308 please follow the <i class="CITETITLE">User Manual</i> chapters <a
309 href="../user-manual/installation.html" target="_top">2.
310 Installation</a> and <a href="../user-manual/startup.html" target=
311 "_top">5. Startup</a> to make sure <span class=
312 "APPLICATION">Privoxy</span> itself is setup correctly.
315 If it is, refer to <a href=
316 "https://www.torproject.org/documentation.html" target="_top">Tor's
317 extensive documentation</a> to learn how to install <span class=
318 "APPLICATION">Tor</span>, and make sure <span class=
319 "APPLICATION">Tor</span>'s logfile says that <span class=
320 "QUOTE">"Tor has successfully opened a circuit"</span> and it <span
321 class="QUOTE">"looks like client functionality is working"</span>.
324 If either <span class="APPLICATION">Tor</span> or <span class=
325 "APPLICATION">Privoxy</span> isn't working, their combination most
326 likely will neither. Testing them on their own will also help you
327 to direct problem reports to the right audience. If <span class=
328 "APPLICATION">Privoxy</span> isn't working, don't bother the <span
329 class="APPLICATION">Tor</span> developers. If <span class=
330 "APPLICATION">Tor</span> isn't working, don't send bug reports to
331 the <span class="APPLICATION">Privoxy</span> Team.
334 If you verified that <span class="APPLICATION">Privoxy</span> and
335 <span class="APPLICATION">Tor</span> are working, it is time to
336 connect them. As far as <span class="APPLICATION">Privoxy</span> is
337 concerned, <span class="APPLICATION">Tor</span> is just another
338 proxy that can be reached by socks4, socks4a and socks5. Most
339 likely you are interested in <span class="APPLICATION">Tor</span>
340 to increase your anonymity level, therefore you should use socks5,
341 to make sure DNS requests are done through <span class=
342 "APPLICATION">Tor</span> and thus invisible to your local network.
343 Using socks4a would work too, but with socks5 you get more precise
347 Since <span class="APPLICATION">Privoxy</span> 3.0.5, its <a href=
348 "../user-manual/config.html" target="_top">main configuration
349 file</a> is already prepared for <span class=
350 "APPLICATION">Tor</span>, if you are using a default <span class=
351 "APPLICATION">Tor</span> configuration and run it on the same
352 system as <span class="APPLICATION">Privoxy</span>, you just have
353 to edit the <a href="../user-manual/config.html#FORWARDING" target=
354 "_top">forwarding section</a> and uncomment the line:
358 <table border="0" bgcolor="#E0E0E0" width="100%">
362 # forward-socks5 / 127.0.0.1:9050 .
369 This is enough to reach the Internet, but additionally you might
370 want to uncomment the following forward rules, to make sure your
371 local network is still reachable through Privoxy:
375 <table border="0" bgcolor="#E0E0E0" width="100%">
379 # forward 192.168.*.*/ .
380 # forward 10.*.*.*/ .
381 # forward 127.*.*.*/ .
388 Unencrypted connections to systems in these address ranges will be
389 as (un)secure as the local network is, but the alternative is that
390 your browser can't reach the network at all. Then again, that may
391 actually be desired and if you don't know for sure that your
392 browser has to be able to reach the local network, there's no
396 If you want your browser to be able to reach servers in your local
397 network by using their names, you will need additional exceptions
402 <table border="0" bgcolor="#E0E0E0" width="100%">
406 # forward localhost/ .
413 Save the modified configuration file and open <a href=
414 "http://config.privoxy.org/show-status" target=
415 "_top">http://config.privoxy.org/show-status/</a> in your browser,
416 confirm that <span class="APPLICATION">Privoxy</span> has reloaded
417 its configuration and that there are no other forward lines, unless
418 you know that you need them. If everything looks good, refer to <a
420 "https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#IsMyConnectionPrivate"
421 target="_top">Tor Faq 4.2</a> to learn how to verify that you are
422 really using <span class="APPLICATION">Tor</span>.
425 Afterward, please take the time to at least skim through the rest
426 of <span class="APPLICATION">Tor's</span> documentation. Make sure
427 you understand what <span class="APPLICATION">Tor</span> does, why
428 it is no replacement for application level security, and why you
429 probably don't want to use it for unencrypted logins.
434 <a name="AEN868">4.11. Might some things break because header
435 information or content is being altered?</a>
438 Definitely. It is common for sites to use browser type, browser
439 version, HTTP header content, and various other techniques in order
440 to dynamically decide what to display and how to display it. What
441 you see, and what I see, might be very different. There are many,
442 many ways that this can be handled, so having hard and fast rules,
446 The <span class="QUOTE">"User-Agent"</span> is sometimes used in
447 this way to identify the browser, and adjust content accordingly.
450 Also, different browsers use different encodings of non-English
451 characters, certain web servers convert pages on-the-fly according
452 to the User Agent header. Giving a <span class="QUOTE">"User
453 Agent"</span> with the wrong operating system or browser
454 manufacturer causes some sites in these languages to be garbled;
455 Surfers to Eastern European sites should change it to something
456 closer. And then some page access counters work by looking at the
457 <span class="QUOTE">"Referer"</span> header; they may fail or break
458 if unavailable. The weather maps of Intellicast have been blocked
459 by their server when no <span class="QUOTE">"Referer"</span> or
460 cookie is provided, is another example. (But you can forge both
461 headers without giving information away). There are many other ways
462 things can go wrong when trying to fool a web server. The results
463 of which could inadvertently cause pages to load incorrectly,
464 partially, or even not at all. And there may be no obvious clues as
465 to just what went wrong, or why. Nowhere will there be a message
466 that says <span class="QUOTE">"<span class="emphasis"><i class=
467 "EMPHASIS">Turn off <tt class="LITERAL">fast-redirects</tt> or
468 else!</i></span> "</span>
471 Similar thoughts apply to modifying JavaScript, and, to a lesser
472 degree, HTML elements.
475 If you have problems with a site, you will have to adjust your
476 configuration accordingly. Cookies are probably the most likely
477 adjustment that may be required, but by no means the only one.
482 <a name="AEN882">4.12. Can Privoxy act as a <span class=
483 "QUOTE">"caching"</span> proxy to speed up web browsing?</a>
486 No, it does not have this ability at all. You want something like
487 <a href="http://www.squid-cache.org/" target="_top">Squid</a> or <a
488 href="http://www.pps.jussieu.fr/~jch/software/polipo/" target=
489 "_top">Polipo</a> for this. And, yes, before you ask, <span class=
490 "APPLICATION">Privoxy</span> can co-exist with other kinds of
491 proxies like <span class="APPLICATION">Squid</span>. See the <a
492 href="../user-manual/config.html#FORWARDING" target=
493 "_top">forwarding chapter</a> in the <a href=
494 "../user-manual/index.html" target="_top">user manual</a> for
500 <a name="AEN892">4.13. What about as a firewall? Can Privoxy
504 Not in the way you mean, or in the way some firewall vendors claim
505 they can. <span class="APPLICATION">Privoxy</span> can help protect
506 your privacy, but can't protect your system from intrusion
507 attempts. It is, of course, perfectly possible to use <span class=
508 "emphasis"><i class="EMPHASIS">both</i></span>.
513 <a name="AEN897">4.14. I have large empty spaces / a checkerboard
514 pattern now where ads used to be. Why?</a>
517 It is technically possible to eliminate banners and ads in a way
518 that frees their allocated page space. This could easily be done by
519 blocking with <span class="APPLICATION">Privoxy's</span> filters,
520 and eliminating the <span class="emphasis"><i class=
521 "EMPHASIS">entire</i></span> image references from the HTML page
525 But, this would consume considerably more CPU resources (IOW, slow
526 things down), would likely destroy the layout of some web pages
527 which rely on the banners utilizing a certain amount of page space,
528 and might fail in other cases, where the screen space is reserved
529 (e.g. by HTML tables for instance). Also, making ads and banners
530 disappear without any trace complicates troubleshooting, and would
531 sooner or later be problematic.
534 The better alternative is to instead let them stay, and block the
535 resulting requests for the banners themselves as is now the case.
536 This leaves either empty space, or the familiar checkerboard
540 So the developers won't support this in the default configuration,
541 but you can of course define appropriate filters yourself to
547 <a name="AEN905">4.15. How can Privoxy filter Secure (HTTPS)
551 Since secure HTTP connections are encrypted SSL sessions between
552 your browser and the secure site, and are meant to be reliably
553 <span class="emphasis"><i class="EMPHASIS">secure</i></span>, there
554 is little that <span class="APPLICATION">Privoxy</span> can do but
555 hand the raw gibberish data though from one end to the other
559 The only exception to this is blocking by host patterns, as the
560 client needs to tell <span class="APPLICATION">Privoxy</span> the
561 name of the remote server, so that <span class=
562 "APPLICATION">Privoxy</span> can establish the connection. If that
563 name matches a host-only pattern, the connection will be blocked.
566 As far as ad blocking is concerned, this is less of a restriction
567 than it may seem, since ad sources are often identifiable by the
568 host name, and often the banners to be placed in an encrypted page
569 come unencrypted nonetheless for efficiency reasons, which exposes
570 them to the full power of <span class=
571 "APPLICATION">Privoxy</span>'s ad blocking.
574 <span class="QUOTE">"Content cookies"</span> (those that are
575 embedded in the actual HTML or JS page content, see <tt class=
577 "../user-manual/actions-file.html#FILTER-CONTENT-COOKIES" target=
578 "_top">filter{content-cookies}</a></tt>), in an SSL transaction
579 will be impossible to block under these conditions. Fortunately,
580 this does not seem to be a very common scenario since most cookies
581 come by traditional means.
586 <a name="AEN919">4.16. Privoxy runs as a <span class=
587 "QUOTE">"server"</span>. How secure is it? Do I need to take any
588 special precautions?</a>
591 On Unix-like systems, <span class="APPLICATION">Privoxy</span> can
592 run as a non-privileged user, which is how we recommend it be run.
593 Also, by default <span class="APPLICATION">Privoxy</span> listens
594 to requests from <span class="QUOTE">"localhost"</span> only.
597 The server aspect of <span class="APPLICATION">Privoxy</span> is
598 not itself directly exposed to the Internet in this configuration.
599 If you want to have <span class="APPLICATION">Privoxy</span> serve
600 as a LAN proxy, this will have to be opened up to allow for LAN
601 requests. In this case, we'd recommend you specify only the LAN
602 gateway address, e.g. 192.168.1.1, in the main <span class=
603 "APPLICATION">Privoxy</span> configuration file and check all <a
604 href="../user-manual/config.html#ACCESS-CONTROL" target=
605 "_top">access control and security options</a>. All LAN hosts can
606 then use this as their proxy address in the browser proxy
607 configuration, but <span class="APPLICATION">Privoxy</span> will
608 not listen on any external interfaces. ACLs can be defined in
609 addition, and using a firewall is always good too. Better safe than
615 <a name="TURNOFF">4.17. Can I temporarily disable Privoxy?</a>
618 <span class="APPLICATION">Privoxy</span> doesn't have a transparent
619 proxy mode, but you can toggle off blocking and content filtering.
622 The easiest way to do that is to point your browser to the remote
623 toggle URL: <a href="http://config.privoxy.org/toggle" target=
624 "_top">http://config.privoxy.org/toggle</a>.
627 See the <a href="../user-manual/appendix.html#BOOKMARKLETS" target=
628 "_top">Bookmarklets section</a> of the <i class="CITETITLE">User
629 Manual</i> for an easy way to access this feature. Note that this
630 is a feature that may need to be enabled in the main <tt class=
631 "FILENAME">config</tt> file.
636 <a name="REALLYOFF">4.18. When <span class=
637 "QUOTE">"disabled"</span> is Privoxy totally out of the
641 No, this just means all optional filtering and actions are
642 disabled. <span class="APPLICATION">Privoxy</span> is still acting
643 as a proxy, but just doing less of the things that <span class=
644 "APPLICATION">Privoxy</span> would normally be expected to do. It
645 is still a <span class="QUOTE">"middle-man"</span> in the
646 interaction between your browser and web sites. See below to bypass
652 <a name="TURNOFF2">4.19. How can I tell Privoxy to totally ignore
656 Bypassing a proxy, or proxying based on arbitrary criteria, is
657 purely a browser configuration issue, not a <span class=
658 "APPLICATION">Privoxy</span> issue. Modern browsers typically do
659 have settings for not proxying certain sites. Check your browser's
665 <a name="CRUNCH">4.20. My logs show Privoxy <span class=
666 "QUOTE">"crunches"</span> ads, but also its own internal CGI pages.
667 What is a <span class="QUOTE">"crunch"</span>?</a>
670 A <span class="QUOTE">"crunch"</span> simply means <span class=
671 "APPLICATION">Privoxy</span> intercepted <span class="emphasis"><i
672 class="EMPHASIS">something</i></span>, nothing more. Often this is
673 indeed ads or banners, but <span class="APPLICATION">Privoxy</span>
674 uses the same mechanism for trapping requests for its own internal
675 pages. For instance, a request for <span class=
676 "APPLICATION">Privoxy's</span> configuration page at: <a href=
677 "http://config.privoxy.org" target=
678 "_top">http://config.privoxy.org</a>, is intercepted (i.e. it does
679 not go out to the 'net), and the familiar CGI configuration is
680 returned to the browser, and the log consequently will show a <span
681 class="QUOTE">"crunch"</span>.
684 Since version 3.0.7, Privoxy will also log the crunch reason. If
685 you are using an older version you might want to upgrade.
690 <a name="DOWNLOADS">4.21. Can Privoxy effect files that I download
691 from a webserver? FTP server?</a>
694 From the webserver's perspective, there is no difference between
695 viewing a document (i.e. a page), and downloading a file. The same
696 is true of <span class="APPLICATION">Privoxy</span>. If there is a
697 match for a <tt class="LITERAL"><a href=
698 "../user-manual/actions-file.html#BLOCK" target=
699 "_top">block</a></tt> pattern, it will still be blocked, and of
700 course this is obvious.
703 Filtering is potentially more of a concern since the results are
704 not always so obvious, and the effects of filtering are there
705 whether the file is simply viewed, or downloaded. And potentially
706 whether the content is some obnoxious advertisement, or Mr. Jimmy's
707 latest/greatest source code jewel. Of course, one of these
708 presumably is <span class="QUOTE">"bad"</span> content that we
709 don't want, and the other is <span class="QUOTE">"good"</span>
710 content that we do want. <span class="APPLICATION">Privoxy</span>
711 is blind to the differences, and can only distinguish <span class=
712 "QUOTE">"good from bad"</span> by the configuration parameters
713 <span class="emphasis"><i class="EMPHASIS">we</i></span> give it.
716 <span class="APPLICATION">Privoxy</span> knows the differences in
717 files according to the <span class="QUOTE">"Content Type"</span> as
718 reported by the webserver. If this is reported accurately (e.g.
719 <span class="QUOTE">"application/zip"</span> for a zip archive),
720 then <span class="APPLICATION">Privoxy</span> knows to ignore these
721 where appropriate. <span class="APPLICATION">Privoxy</span>
722 potentially can filter HTML as well as plain text documents,
723 subject to configuration parameters of course. Also, documents that
724 are of an unknown type (generally assumed to be <span class=
725 "QUOTE">"text/plain"</span>) can be filtered, as will those that
726 might be incorrectly reported by the webserver. If such a file is a
727 downloaded file that is intended to be saved to disk, then any
728 content that might have been altered by filtering, will be saved
729 too, for these (probably rare) cases.
732 Note that versions later than 3.0.2 do NOT filter document types
733 reported as <span class="QUOTE">"text/plain"</span>. Prior to this,
734 <span class="APPLICATION">Privoxy</span> did filter this document
738 In short, filtering is <span class="QUOTE">"ON"</span> if a) the
739 content type as reported by the webserver is appropriate <span
740 class="emphasis"><i class="EMPHASIS">and</i></span> b) the
741 configuration allows it (or at least does not disallow it). That's
742 it. There is no magic cookie anywhere to say this is <span class=
743 "QUOTE">"good"</span> and this is <span class="QUOTE">"bad"</span>.
744 It's the configuration that lets it all happen or not.
747 If you download text files, you probably do not want these to be
748 filtered, particularly if the content is source code, or other
749 critical content. Source code sometimes might be mistaken for
750 Javascript (i.e. the kind that might open a pop-up window). It is
751 recommended to turn off filtering for download sites (particularly
752 if the content may be plain text files and you are using version
753 3.0.2 or earlier) in your <tt class="FILENAME">user.action</tt>
754 file. And also, for any site or page where making <span class=
755 "emphasis"><i class="EMPHASIS">any</i></span> changes at all to the
756 content is to be avoided.
759 <span class="APPLICATION">Privoxy</span> does not do FTP at all,
760 only HTTP and HTTPS (SSL) protocols.
765 <a name="DOWNLOADS2">4.22. I just downloaded a Perl script, and
766 Privoxy altered it! Yikes, what is wrong!</a>
774 <a name="HOSTSFILE">4.23. Should I continue to use a <span class=
775 "QUOTE">"HOSTS"</span> file for ad-blocking?</a>
778 One time-tested technique to defeat common ads is to trick the
779 local DNS system by giving a phony IP address for the ad generator
780 in the local <tt class="FILENAME">HOSTS</tt> file, typically using
781 <tt class="LITERAL">127.0.0.1</tt>, aka <tt class=
782 "LITERAL">localhost</tt>. This effectively blocks the ad.
785 There is no reason to use this technique in conjunction with <span
786 class="APPLICATION">Privoxy</span>. <span class=
787 "APPLICATION">Privoxy</span> does essentially the same thing, much
788 more elegantly and with much more flexibility. A large <tt class=
789 "FILENAME">HOSTS</tt> file, in fact, not only duplicates effort,
790 but may get in the way and seriously slow down your system. It is
791 recommended to remove such entries from your <tt class=
792 "FILENAME">HOSTS</tt> file. If you think your hosts list is
793 neglected by <span class="APPLICATION">Privoxy's</span>
794 configuration, consider adding your list to your <tt class=
795 "FILENAME">user.action</tt> file:
799 <table border="0" bgcolor="#E0E0E0" width="100%">
806 ads.galore.example.com
815 <a name="SEEALSO">4.24. Where can I find more information about
816 Privoxy and related issues?</a>
819 Other references and sites of interest to <span class=
820 "APPLICATION">Privoxy</span> users:
828 <a href="http://www.privoxy.org/" target=
829 "_top">http://www.privoxy.org/</a>, the <span class=
830 "APPLICATION">Privoxy</span> Home page.
839 <a href="http://www.privoxy.org/faq/" target=
840 "_top">http://www.privoxy.org/faq/</a>, the <span class=
841 "APPLICATION">Privoxy</span> FAQ.
850 <a href="http://www.privoxy.org/developer-manual/" target=
851 "_top">http://www.privoxy.org/developer-manual/</a>, the
852 <span class="APPLICATION">Privoxy</span> developer manual.
861 <a href="https://sourceforge.net/projects/ijbswa/" target=
862 "_top">https://sourceforge.net/projects/ijbswa/</a>, the
863 Project Page for <span class="APPLICATION">Privoxy</span> on
864 <a href="http://sourceforge.net" target=
865 "_top">SourceForge</a>.
874 <a href="http://config.privoxy.org/" target=
875 "_top">http://config.privoxy.org/</a>, the web-based user
876 interface. <span class="APPLICATION">Privoxy</span> must be
877 running for this to work. Shortcut: <a href="http://p.p/"
878 target="_top">http://p.p/</a>
888 "https://sourceforge.net/tracker/?group_id=11118&atid=460288"
890 "_top">https://sourceforge.net/tracker/?group_id=11118&atid=460288</a>,
891 to submit <span class="QUOTE">"misses"</span> and other
892 configuration related suggestions to the developers.
901 <a href="http://www.junkbusters.com/ht/en/cookies.html"
903 "_top">http://www.junkbusters.com/ht/en/cookies.html</a>, an
904 explanation how cookies are used to track web users.
913 <a href="http://www.junkbusters.com/ijb.html" target=
914 "_top">http://www.junkbusters.com/ijb.html</a>, the original
924 <a href="http://www.squid-cache.org/" target=
925 "_top">http://www.squid-cache.org/</a>, a popular caching
926 proxy, which is often used together with <span class=
927 "APPLICATION">Privoxy</span>.
936 <a href="http://www.pps.jussieu.fr/~jch/software/polipo/"
938 "_top">http://www.pps.jussieu.fr/~jch/software/polipo/</a>,
939 <span class="APPLICATION">Polipo</span> is a caching proxy
940 with advanced features like pipelining, multiplexing and
941 caching of partial instances. In many setups it can be used
942 as <span class="APPLICATION">Squid</span> replacement.
951 <a href="https://www.torproject.org/" target=
952 "_top">https://www.torproject.org/</a>, <span class=
953 "APPLICATION">Tor</span> can help anonymize web browsing, web
954 publishing, instant messaging, IRC, SSH, and other
963 <a name="MICROSUCK">4.25. I've noticed that Privoxy changes <span
964 class="QUOTE">"Microsoft"</span> to <span class=
965 "QUOTE">"MicroSuck"</span>! Why are you manipulating my
969 We're not. The text substitutions that you are seeing are disabled
970 in the default configuration as shipped. You have either manually
971 activated the <span class="QUOTE">"<tt class=
972 "LITERAL">fun</tt>"</span> filter which is clearly labeled <span
973 class="QUOTE">"Text replacements for subversive browsing
974 fun!"</span> or you are using an older Privoxy version and have
975 implicitly activated it by choosing the <span class=
976 "QUOTE">"Advanced"</span> profile in the web-based editor. Please
982 <a name="VALID">4.26. Does Privoxy produce <span class=
983 "QUOTE">"valid"</span> HTML (or XHTML)?</a>
986 Privoxy generates HTML in both its own <span class=
987 "QUOTE">"templates"</span>, and possibly whenever there are text
988 substitutions via a <span class="APPLICATION">Privoxy</span>
989 filter. While this should always conform to the HTML 4.01
990 specifications, it has not been validated against this or any other
996 <a name="SURPRISE-PRIVOXY">4.27. How did you manage to get Privoxy
997 on my computer without my consent?</a>
1000 We didn't. We make Privoxy available for download, but we don't go
1001 around installing it on other people's systems behind their back.
1002 If you discover Privoxy running on your system and are sure you
1003 didn't install it yourself, somebody else did. You may not even be
1004 running the real Privoxy, but maybe something else that only
1005 pretends to be Privoxy, or maybe something that is based on the
1006 real Privoxy, but has been modified.
1009 Lately there have been reports of problems with some kind of
1010 Privoxy versions that come preinstalled on some Netbooks. Some of
1011 the problems described are inconsistent with the behaviour of
1012 official Privoxy versions, which suggests that the preinstalled
1013 software may contain vendor modifications that we don't know about
1014 and thus can't debug.
1017 Privoxy's <a href="copyright.html">license</a> allows vendor
1018 modifications, but the vendor has to comply with the license, which
1019 involves informing the user about the changes and to make the
1020 changes available under the same license as Privoxy itself.
1023 If you are having trouble with a modified Privoxy version, please
1024 try to talk to whoever made the modifications before reporting the
1025 problem to us. Please also try to convince whoever made the
1026 modifications to talk to us. If you think somebody gave you a
1027 modified Privoxy version without complying to the license, please
1032 <div class="NAVFOOTER">
1033 <hr width="100%" class="c1">
1034 <table summary="Footer navigation table" width="100%" border="0"
1035 cellpadding="0" cellspacing="0">
1037 <td width="33%" align="left" valign="top">
1038 <a href="configuration.html" accesskey="P">Prev</a>
1040 <td width="34%" align="center" valign="top">
1041 <a href="index.html" accesskey="H">Home</a>
1043 <td width="33%" align="right" valign="top">
1044 <a href="trouble.html" accesskey="N">Next</a>
1048 <td width="33%" align="left" valign="top">
1051 <td width="34%" align="center" valign="top">
1054 <td width="33%" align="right" valign="top">