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41 <h1 class="SECT1"><a name="MISC" id="MISC">4. Miscellaneous</a></h1>
44 <h3 class="SECT2"><a name="SLOWSME" id="SLOWSME">4.1. How much does
45 Privoxy slow my browsing down? This has to add extra time to
48 <p>How much of an impact depends on many things, including the CPU of
49 the host system, how aggressive the configuration is, which specific
50 actions are being triggered, the size of the page, the bandwidth of the
53 <p>Overall, it should not slow you down any in real terms, and may
54 actually help speed things up since ads, banners and other junk are not
55 typically being retrieved and displayed. The actual processing time
56 required by <span class="APPLICATION">Privoxy</span> itself for each
57 page, is relatively small in the overall scheme of things, and happens
58 very quickly. This is typically more than offset by time saved not
59 downloading and rendering ad images and other junk content (if ad
60 blocking is being used).</p>
62 <p><span class="QUOTE">"Filtering"</span> content via the <tt class=
63 "LITERAL"><a href="../user-manual/actions-file.html#FILTER" target=
64 "_top">filter</a></tt> or <tt class="LITERAL"><a href=
65 "../user-manual/actions-file.html#DEANIMATE-GIFS" target=
66 "_top">deanimate-gifs</a></tt> actions may cause a perceived slowdown,
67 since the entire document needs to be buffered before displaying. And
68 on very large documents, filtering may have some measurable impact. How
69 much depends on the page size, the actual definition of the filter(s),
70 etc. See below. Most other actions have little to no impact on
73 <p>Also, when filtering is enabled but zlib support isn't available,
74 compression is often disabled (see <a href=
75 "../user-manual/actions-file.html#PREVENT-COMPRESSION" target=
76 "_top">prevent-compression</a>). This can have an impact on speed as
77 well, although it's probably smaller than you might think. Again, the
78 page size, etc. will determine how much of an impact.</p>
82 <h3 class="SECT2"><a name="LOADINGTIMES" id="LOADINGTIMES">4.2. I
83 notice considerable delays in page requests. What's wrong?</a></h3>
85 <p>If you use any <tt class="LITERAL"><a href=
86 "../user-manual/actions-file.html#FILTER" target="_top">filter</a></tt>
87 action, such as filtering banners by size, web-bugs etc, or the
88 <tt class="LITERAL"><a href=
89 "../user-manual/actions-file.html#DEANIMATE-GIFS" target=
90 "_top">deanimate-gifs</a></tt> action, the entire document must be
91 loaded into memory in order for the filtering mechanism to work, and
92 nothing is sent to the browser during this time.</p>
94 <p>The loading time typically does not really change much in real
95 numbers, but the feeling is different, because most browsers are able
96 to start rendering incomplete content, giving the user a feeling of "it
97 works". This effect is more noticeable on slower dialup connections.
98 Extremely large documents may have some impact on the time to load the
99 page where there is filtering being done. But overall, the difference
100 should be very minimal. If there is a big impact, then probably some
101 other situation is contributing (like anti-virus software).</p>
103 <p>Filtering is automatically disabled for inappropriate MIME types.
104 But note that if the web server mis-reports the MIME type, then content
105 that should not be filtered, could be. <span class=
106 "APPLICATION">Privoxy</span> only knows how to differentiate filterable
107 content because of the MIME type as reported by the server, or because
108 of some configuration setting that enables/disables filtering.</p>
112 <h3 class="SECT2"><a name="CONFIGURL" id="CONFIGURL">4.3. What are
113 "http://config.privoxy.org/" and "http://p.p/"?</a></h3>
115 <p><a href="http://config.privoxy.org/" target=
116 "_top">http://config.privoxy.org/</a> is the address of <span class=
117 "APPLICATION">Privoxy</span>'s built-in user interface, and <a href=
118 "http://p.p/" target="_top">http://p.p/</a> is a shortcut for it.</p>
120 <p>Since <span class="APPLICATION">Privoxy</span> sits between your web
121 browser and the Internet, it can simply intercept requests for these
122 addresses and answer them with its built-in <span class="QUOTE">"web
125 <p>This also makes for a good test for your browser configuration: If
126 entering the URL <a href="http://config.privoxy.org/" target=
127 "_top">http://config.privoxy.org/</a> takes you to a page saying
128 <span class="QUOTE">"This is Privoxy ..."</span>, everything is OK. If
129 you get a page saying <span class="QUOTE">"Privoxy is not
130 working"</span> instead, then your browser didn't use <span class=
131 "APPLICATION">Privoxy</span> for the request, hence it could not be
132 intercepted, and you have accessed the <span class="emphasis"><i class=
133 "EMPHASIS">real</i></span> web site at config.privoxy.org.</p>
135 <p>Note that config.privoxy.org resolves to a public IP address. If you
136 use config.privoxy.org as ping or traceroute target you will reach the
137 system on the Internet (Privoxy can't intercept ICMP requests). If you
138 want to ping the system Privoxy runs on, you should use its IP address
139 or local DNS name (if it has got one).</p>
143 <h3 class="SECT2"><a name="NEWADS" id="NEWADS">4.4. How can I submit
144 new ads, or report problems?</a></h3>
146 <p>Please see the <a href="contact.html">Contact section</a> for
147 various ways to interact with the developers.</p>
151 <h3 class="SECT2"><a name="NEWADS2" id="NEWADS2">4.5. If I do submit
152 missed ads, will they be included in future updates?</a></h3>
154 <p>Whether such submissions are eventually included in the <tt class=
155 "FILENAME">default.action</tt> configuration file depends on how
156 significant the issue is. We of course want to address any potential
157 problem with major, high-profile sites such as <i class=
158 "CITETITLE">Google</i>, <i class="CITETITLE">Yahoo</i>, etc. Any site
159 with global or regional reach, has a good chance of being a candidate.
160 But at the other end of the spectrum are any number of smaller,
161 low-profile sites such as for local clubs or schools. Since their reach
162 and impact are much less, they are best handled by inclusion in the
163 user's <tt class="FILENAME">user.action</tt>, and thus would be
164 unlikely to be included.</p>
168 <h3 class="SECT2"><a name="NOONECARES" id="NOONECARES">4.6. Why doesn't
169 anyone answer my support request?</a></h3>
171 <p>Rest assured that it has been read and considered. Why it is not
172 answered, could be for various reasons, including no one has a good
173 answer for it, no one has had time to yet investigate it thoroughly, it
174 has been reported numerous times already, or because not enough
175 information was provided to help us help you. Your efforts are not
176 wasted, and we do appreciate them.</p>
180 <h3 class="SECT2"><a name="IP" id="IP">4.7. How can I hide my IP
183 <p>If you run both the browser and <span class=
184 "APPLICATION">Privoxy</span> locally, you cannot hide your IP address
185 with <span class="APPLICATION">Privoxy</span> or ultimately any other
186 software alone. The server needs to know your IP address so that it
187 knows where to send the responses back.</p>
189 <p>There are many publicly usable "anonymous" proxies out there, which
190 provide a further level of indirection between you and the web
193 <p>However, these proxies are called "anonymous" because you don't need
194 to authenticate, not because they would offer any real anonymity. Most
195 of them will log your IP address and make it available to the
196 authorities in case you violate the law of the country they run in. In
197 fact you can't even rule out that some of them only exist to *collect*
198 information on (those suspicious) people with a more than average
199 preference for privacy.</p>
201 <p>If you want to hide your IP address from most adversaries, you
202 should consider chaining <span class="APPLICATION">Privoxy</span> with
203 <a href="https://www.torproject.org/" target="_top">Tor</a>. The
204 configuration details can be found in <a href="#TOR" target="_top">How
205 do I use <span class="APPLICATION">Privoxy</span> together with
206 <span class="APPLICATION">Tor</span> section</a> just below.</p>
210 <h3 class="SECT2"><a name="ANONFORSURE" id="ANONFORSURE">4.8. Can
211 Privoxy guarantee I am anonymous?</a></h3>
213 <p>No. Your chances of remaining anonymous are improved, but unless you
214 <a href="#TOR" target="_top">chain <span class=
215 "APPLICATION">Privoxy</span> with <span class=
216 "APPLICATION">Tor</span></a> or a similar proxy and know what you're
217 doing when it comes to configuring the rest of your system, you should
218 assume that everything you do on the Web can be traced back to you.</p>
220 <p><span class="APPLICATION">Privoxy</span> can remove various
221 information about you, and allows <span class="emphasis"><i class=
222 "EMPHASIS">you</i></span> more freedom to decide which sites you can
223 trust, and what details you want to reveal. But it neither hides your
224 IP address, nor can it guarantee that the rest of the system behaves
225 correctly. There are several possibilities how a web sites can find out
226 who you are, even if you are using a strict <span class=
227 "APPLICATION">Privoxy</span> configuration and chained it with
228 <span class="APPLICATION">Tor</span>.</p>
230 <p>Most of <span class="APPLICATION">Privoxy's</span> privacy-enhancing
231 features can be easily subverted by an insecure browser configuration,
232 therefore you should use a browser that can be configured to only
233 execute code from trusted sites, and be careful which sites you trust.
234 For example there is no point in having <span class=
235 "APPLICATION">Privoxy</span> modify the User-Agent header, if websites
236 can get all the information they want through JavaScript, ActiveX,
239 <p>A few browsers disclose the user's email address in certain
240 situations, such as when transferring a file by FTP. <span class=
241 "APPLICATION">Privoxy</span> does not filter FTP. If you need this
242 feature, or are concerned about the mail handler of your browser
243 disclosing your email address, you might consider products such as
244 <span class="APPLICATION">NSClean</span>.</p>
246 <p>Browsers available only as binaries could use non-standard headers
247 to give out any information they can have access to: see the
248 manufacturer's license agreement. It's impossible to anticipate and
249 prevent every breach of privacy that might occur. The professionally
250 paranoid prefer browsers available as source code, because anticipating
251 their behavior is easier. Trust the source, Luke!</p>
255 <h3 class="SECT2"><a name="PROXYTEST" id="PROXYTEST">4.9. A test site
256 says I am not using a Proxy.</a></h3>
258 <p>Good! Actually, they are probably testing for some other kinds of
259 proxies. Hiding yourself completely would require additional steps.</p>
263 <h3 class="SECT2"><a name="TOR" id="TOR">4.10. How do I use Privoxy
264 together with Tor?</a></h3>
266 <p>Before you configure <span class="APPLICATION">Privoxy</span> to use
267 <a href="https://www.torproject.org/" target="_top">Tor</a>, please
268 follow the <i class="CITETITLE">User Manual</i> chapters <a href=
269 "../user-manual/installation.html" target="_top">2. Installation</a>
270 and <a href="../user-manual/startup.html" target="_top">5. Startup</a>
271 to make sure <span class="APPLICATION">Privoxy</span> itself is setup
274 <p>If it is, refer to <a href=
275 "https://www.torproject.org/documentation.html" target="_top">Tor's
276 extensive documentation</a> to learn how to install <span class=
277 "APPLICATION">Tor</span>, and make sure <span class=
278 "APPLICATION">Tor</span>'s logfile says that <span class="QUOTE">"Tor
279 has successfully opened a circuit"</span> and it <span class=
280 "QUOTE">"looks like client functionality is working"</span>.</p>
282 <p>If either <span class="APPLICATION">Tor</span> or <span class=
283 "APPLICATION">Privoxy</span> isn't working, their combination most
284 likely will neither. Testing them on their own will also help you to
285 direct problem reports to the right audience. If <span class=
286 "APPLICATION">Privoxy</span> isn't working, don't bother the
287 <span class="APPLICATION">Tor</span> developers. If <span class=
288 "APPLICATION">Tor</span> isn't working, don't send bug reports to the
289 <span class="APPLICATION">Privoxy</span> Team.</p>
291 <p>If you verified that <span class="APPLICATION">Privoxy</span> and
292 <span class="APPLICATION">Tor</span> are working, it is time to connect
293 them. As far as <span class="APPLICATION">Privoxy</span> is concerned,
294 <span class="APPLICATION">Tor</span> is just another proxy that can be
295 reached by socks4, socks4a and socks5. Most likely you are interested
296 in <span class="APPLICATION">Tor</span> to increase your anonymity
297 level, therefore you should use socks5, to make sure DNS requests are
298 done through <span class="APPLICATION">Tor</span> and thus invisible to
299 your local network. Using socks4a would work too, but with socks5 you
300 get more precise error messages.</p>
302 <p><span class="APPLICATION">Privoxy's</span> <a href=
303 "../user-manual/config.html" target="_top">main configuration file</a>
304 is already prepared for <span class="APPLICATION">Tor</span>, if you
305 are using a default <span class="APPLICATION">Tor</span> configuration
306 and run it on the same system as <span class=
307 "APPLICATION">Privoxy</span>, you just have to edit the <a href=
308 "../user-manual/config.html#FORWARDING" target="_top">forwarding
309 section</a> and uncomment the line:</p>
311 <table border="0" bgcolor="#E0E0E0" width="100%">
315 # forward-socks5t / 127.0.0.1:9050 .
322 <p>Note that if you got Tor through one of the bundles, you may have to
323 change the port from 9050 to 9150 (or even another one). For details,
324 please check the documentation on the <a href="https://torproject.org/"
325 target="_top">Tor website</a>.</p>
327 <p>This is enough to reach the Internet, but additionally you might
328 want to uncomment the following forward rules, to make sure your local
329 network is still reachable through Privoxy:</p>
331 <table border="0" bgcolor="#E0E0E0" width="100%">
335 # forward 192.168.*.*/ .
336 # forward 10.*.*.*/ .
337 # forward 127.*.*.*/ .
344 <p>Unencrypted connections to systems in these address ranges will be
345 as (un)secure as the local network is, but the alternative is that your
346 browser can't reach the network at all. Then again, that may actually
347 be desired and if you don't know for sure that your browser has to be
348 able to reach the local network, there's no reason to allow it.</p>
350 <p>If you want your browser to be able to reach servers in your local
351 network by using their names, you will need additional exceptions that
354 <table border="0" bgcolor="#E0E0E0" width="100%">
358 # forward localhost/ .
365 <p>Save the modified configuration file and open <a href=
366 "http://config.privoxy.org/show-status" target=
367 "_top">http://config.privoxy.org/show-status</a> in your browser,
368 confirm that <span class="APPLICATION">Privoxy</span> has reloaded its
369 configuration and that there are no other forward lines, unless you
370 know that you need them. If everything looks good, refer to <a href=
371 "https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#IsMyConnectionPrivate"
372 target="_top">Tor Faq 4.2</a> to learn how to verify that you are
373 really using <span class="APPLICATION">Tor</span>.</p>
375 <p>Afterward, please take the time to at least skim through the rest of
376 <span class="APPLICATION">Tor's</span> documentation. Make sure you
377 understand what <span class="APPLICATION">Tor</span> does, why it is no
378 replacement for application level security, and why you probably don't
379 want to use it for unencrypted logins.</p>
383 <h3 class="SECT2"><a name="SITEBREAK" id="SITEBREAK">4.11. Might some
384 things break because header information or content is being
387 <p>Definitely. It is common for sites to use browser type, browser
388 version, HTTP header content, and various other techniques in order to
389 dynamically decide what to display and how to display it. What you see,
390 and what I see, might be very different. There are many, many ways that
391 this can be handled, so having hard and fast rules, is tricky.</p>
393 <p>The <span class="QUOTE">"User-Agent"</span> is sometimes used in
394 this way to identify the browser, and adjust content accordingly.</p>
396 <p>Also, different browsers use different encodings of non-English
397 characters, certain web servers convert pages on-the-fly according to
398 the User Agent header. Giving a <span class="QUOTE">"User Agent"</span>
399 with the wrong operating system or browser manufacturer causes some
400 sites in these languages to be garbled; Surfers to Eastern European
401 sites should change it to something closer. And then some page access
402 counters work by looking at the <span class="QUOTE">"Referer"</span>
403 header; they may fail or break if unavailable. The weather maps of
404 Intellicast have been blocked by their server when no <span class=
405 "QUOTE">"Referer"</span> or cookie is provided, is another example.
406 (But you can forge both headers without giving information away). There
407 are many other ways things can go wrong when trying to fool a web
408 server. The results of which could inadvertently cause pages to load
409 incorrectly, partially, or even not at all. And there may be no obvious
410 clues as to just what went wrong, or why. Nowhere will there be a
411 message that says <span class="QUOTE">"<span class="emphasis"><i class=
412 "EMPHASIS">Turn off <tt class="LITERAL">fast-redirects</tt> or
413 else!</i></span> "</span></p>
415 <p>Similar thoughts apply to modifying JavaScript, and, to a lesser
416 degree, HTML elements.</p>
418 <p>If you have problems with a site, you will have to adjust your
419 configuration accordingly. Cookies are probably the most likely
420 adjustment that may be required, but by no means the only one.</p>
424 <h3 class="SECT2"><a name="CACHING" id="CACHING">4.12. Can Privoxy act
425 as a <span class="QUOTE">"caching"</span> proxy to speed up web
428 <p>No, it does not have this ability at all. You want something like
429 <a href="http://www.squid-cache.org/" target="_top">Squid</a> or
430 <a href="http://www.pps.jussieu.fr/~jch/software/polipo/" target=
431 "_top">Polipo</a> for this. And, yes, before you ask, <span class=
432 "APPLICATION">Privoxy</span> can co-exist with other kinds of proxies
433 like <span class="APPLICATION">Squid</span>. See the <a href=
434 "../user-manual/config.html#FORWARDING" target="_top">forwarding
435 chapter</a> in the <a href="../user-manual/index.html" target=
436 "_top">user manual</a> for details.</p>
440 <h3 class="SECT2"><a name="FIREWALL" id="FIREWALL">4.13. What about as
441 a firewall? Can Privoxy protect me?</a></h3>
443 <p>Not in the way you mean, or in the way some firewall vendors claim
444 they can. <span class="APPLICATION">Privoxy</span> can help protect
445 your privacy, but can't protect your system from intrusion attempts. It
446 is, of course, perfectly possible to use <span class=
447 "emphasis"><i class="EMPHASIS">both</i></span>.</p>
451 <h3 class="SECT2"><a name="WASTED" id="WASTED">4.14. I have large empty
452 spaces / a checkerboard pattern now where ads used to be. Why?</a></h3>
454 <p>It is technically possible to eliminate banners and ads in a way
455 that frees their allocated page space. This could easily be done by
456 blocking with <span class="APPLICATION">Privoxy's</span> filters, and
457 eliminating the <span class="emphasis"><i class=
458 "EMPHASIS">entire</i></span> image references from the HTML page
461 <p>But, this would consume considerably more CPU resources (IOW, slow
462 things down), would likely destroy the layout of some web pages which
463 rely on the banners utilizing a certain amount of page space, and might
464 fail in other cases, where the screen space is reserved (e.g. by HTML
465 tables for instance). Also, making ads and banners disappear without
466 any trace complicates troubleshooting, and would sooner or later be
469 <p>The better alternative is to instead let them stay, and block the
470 resulting requests for the banners themselves as is now the case. This
471 leaves either empty space, or the familiar checkerboard pattern.</p>
473 <p>So the developers won't support this in the default configuration,
474 but you can of course define appropriate filters yourself to achieve
479 <h3 class="SECT2"><a name="SSL" id="SSL">4.15. How can Privoxy filter
480 Secure (HTTPS) URLs?</a></h3>
482 <p>Since secure HTTP connections are encrypted SSL sessions between
483 your browser and the secure site, and are meant to be reliably
484 <span class="emphasis"><i class="EMPHASIS">secure</i></span>, there is
485 little that <span class="APPLICATION">Privoxy</span> can do but hand
486 the raw gibberish data though from one end to the other
489 <p>The only exception to this is blocking by host patterns, as the
490 client needs to tell <span class="APPLICATION">Privoxy</span> the name
491 of the remote server, so that <span class="APPLICATION">Privoxy</span>
492 can establish the connection. If that name matches a host-only pattern,
493 the connection will be blocked.</p>
495 <p>As far as ad blocking is concerned, this is less of a restriction
496 than it may seem, since ad sources are often identifiable by the host
497 name, and often the banners to be placed in an encrypted page come
498 unencrypted nonetheless for efficiency reasons, which exposes them to
499 the full power of <span class="APPLICATION">Privoxy</span>'s ad
502 <p><span class="QUOTE">"Content cookies"</span> (those that are
503 embedded in the actual HTML or JS page content, see <tt class=
505 "../user-manual/actions-file.html#FILTER-CONTENT-COOKIES" target=
506 "_top">filter{content-cookies}</a></tt>), in an SSL transaction will be
507 impossible to block under these conditions. Fortunately, this does not
508 seem to be a very common scenario since most cookies come by
509 traditional means.</p>
513 <h3 class="SECT2"><a name="SECURE" id="SECURE">4.16. Privoxy runs as a
514 <span class="QUOTE">"server"</span>. How secure is it? Do I need to
515 take any special precautions?</a></h3>
517 <p>On Unix-like systems, <span class="APPLICATION">Privoxy</span> can
518 run as a non-privileged user, which is how we recommend it be run.
519 Also, by default <span class="APPLICATION">Privoxy</span> listens to
520 requests from <span class="QUOTE">"localhost"</span> only.</p>
522 <p>The server aspect of <span class="APPLICATION">Privoxy</span> is not
523 itself directly exposed to the Internet in this configuration. If you
524 want to have <span class="APPLICATION">Privoxy</span> serve as a LAN
525 proxy, this will have to be opened up to allow for LAN requests. In
526 this case, we'd recommend you specify only the LAN gateway address,
527 e.g. 192.168.1.1, in the main <span class="APPLICATION">Privoxy</span>
528 configuration file and check all <a href=
529 "../user-manual/config.html#ACCESS-CONTROL" target="_top">access
530 control and security options</a>. All LAN hosts can then use this as
531 their proxy address in the browser proxy configuration, but
532 <span class="APPLICATION">Privoxy</span> will not listen on any
533 external interfaces. ACLs can be defined in addition, and using a
534 firewall is always good too. Better safe than sorry.</p>
538 <h3 class="SECT2"><a name="TURNOFF" id="TURNOFF">4.17. Can I
539 temporarily disable Privoxy?</a></h3>
541 <p><span class="APPLICATION">Privoxy</span> doesn't have a transparent
542 proxy mode, but you can toggle off blocking and content filtering.</p>
544 <p>The easiest way to do that is to point your browser to the remote
545 toggle URL: <a href="http://config.privoxy.org/toggle" target=
546 "_top">http://config.privoxy.org/toggle</a>.</p>
548 <p>See the <a href="../user-manual/appendix.html#BOOKMARKLETS" target=
549 "_top">Bookmarklets section</a> of the <i class="CITETITLE">User
550 Manual</i> for an easy way to access this feature. Note that this is a
551 feature that may need to be enabled in the main <tt class=
552 "FILENAME">config</tt> file.</p>
556 <h3 class="SECT2"><a name="REALLYOFF" id="REALLYOFF">4.18. When
557 <span class="QUOTE">"disabled"</span> is Privoxy totally out of the
560 <p>No, this just means all optional filtering and actions are disabled.
561 <span class="APPLICATION">Privoxy</span> is still acting as a proxy,
562 but just doing less of the things that <span class=
563 "APPLICATION">Privoxy</span> would normally be expected to do. It is
564 still a <span class="QUOTE">"middle-man"</span> in the interaction
565 between your browser and web sites. See below to bypass the proxy.</p>
569 <h3 class="SECT2"><a name="TURNOFF2" id="TURNOFF2">4.19. How can I tell
570 Privoxy to totally ignore certain sites?</a></h3>
572 <p>Bypassing a proxy, or proxying based on arbitrary criteria, is
573 purely a browser configuration issue, not a <span class=
574 "APPLICATION">Privoxy</span> issue. Modern browsers typically do have
575 settings for not proxying certain sites. Check your browser's help
580 <h3 class="SECT2"><a name="CRUNCH" id="CRUNCH">4.20. My logs show
581 Privoxy <span class="QUOTE">"crunches"</span> ads, but also its own
582 internal CGI pages. What is a <span class=
583 "QUOTE">"crunch"</span>?</a></h3>
585 <p>A <span class="QUOTE">"crunch"</span> simply means <span class=
586 "APPLICATION">Privoxy</span> intercepted <span class=
587 "emphasis"><i class="EMPHASIS">something</i></span>, nothing more.
588 Often this is indeed ads or banners, but <span class=
589 "APPLICATION">Privoxy</span> uses the same mechanism for trapping
590 requests for its own internal pages. For instance, a request for
591 <span class="APPLICATION">Privoxy's</span> configuration page at:
592 <a href="http://config.privoxy.org" target=
593 "_top">http://config.privoxy.org</a>, is intercepted (i.e. it does not
594 go out to the 'net), and the familiar CGI configuration is returned to
595 the browser, and the log consequently will show a <span class=
596 "QUOTE">"crunch"</span>.</p>
598 <p>Since version 3.0.7, Privoxy will also log the crunch reason. If you
599 are using an older version you might want to upgrade.</p>
603 <h3 class="SECT2"><a name="DOWNLOADS" id="DOWNLOADS">4.21. Can Privoxy
604 affect files that I download from a webserver? FTP server?</a></h3>
606 <p>From the webserver's perspective, there is no difference between
607 viewing a document (i.e. a page), and downloading a file. The same is
608 true of <span class="APPLICATION">Privoxy</span>. If there is a match
609 for a <tt class="LITERAL"><a href=
610 "../user-manual/actions-file.html#BLOCK" target="_top">block</a></tt>
611 pattern, it will still be blocked, and of course this is obvious.</p>
613 <p>Filtering is potentially more of a concern since the results are not
614 always so obvious, and the effects of filtering are there whether the
615 file is simply viewed, or downloaded. And potentially whether the
616 content is some obnoxious advertisement, or Mr. Jimmy's latest/greatest
617 source code jewel. Of course, one of these presumably is <span class=
618 "QUOTE">"bad"</span> content that we don't want, and the other is
619 <span class="QUOTE">"good"</span> content that we do want. <span class=
620 "APPLICATION">Privoxy</span> is blind to the differences, and can only
621 distinguish <span class="QUOTE">"good from bad"</span> by the
622 configuration parameters <span class="emphasis"><i class=
623 "EMPHASIS">we</i></span> give it.</p>
625 <p><span class="APPLICATION">Privoxy</span> knows the differences in
626 files according to the <span class="QUOTE">"Content Type"</span> as
627 reported by the webserver. If this is reported accurately (e.g.
628 <span class="QUOTE">"application/zip"</span> for a zip archive), then
629 <span class="APPLICATION">Privoxy</span> knows to ignore these where
630 appropriate. <span class="APPLICATION">Privoxy</span> potentially can
631 filter HTML as well as plain text documents, subject to configuration
632 parameters of course. Also, documents that are of an unknown type
633 (generally assumed to be <span class="QUOTE">"text/plain"</span>) can
634 be filtered, as will those that might be incorrectly reported by the
635 webserver. If such a file is a downloaded file that is intended to be
636 saved to disk, then any content that might have been altered by
637 filtering, will be saved too, for these (probably rare) cases.</p>
639 <p>Note that versions later than 3.0.2 do NOT filter document types
640 reported as <span class="QUOTE">"text/plain"</span>. Prior to this,
641 <span class="APPLICATION">Privoxy</span> did filter this document
644 <p>In short, filtering is <span class="QUOTE">"ON"</span> if a) the
645 content type as reported by the webserver is appropriate <span class=
646 "emphasis"><i class="EMPHASIS">and</i></span> b) the configuration
647 allows it (or at least does not disallow it). That's it. There is no
648 magic cookie anywhere to say this is <span class="QUOTE">"good"</span>
649 and this is <span class="QUOTE">"bad"</span>. It's the configuration
650 that lets it all happen or not.</p>
652 <p>If you download text files, you probably do not want these to be
653 filtered, particularly if the content is source code, or other critical
654 content. Source code sometimes might be mistaken for Javascript (i.e.
655 the kind that might open a pop-up window). It is recommended to turn
656 off filtering for download sites (particularly if the content may be
657 plain text files and you are using version 3.0.2 or earlier) in your
658 <tt class="FILENAME">user.action</tt> file. And also, for any site or
659 page where making <span class="emphasis"><i class=
660 "EMPHASIS">any</i></span> changes at all to the content is to be
663 <p><span class="APPLICATION">Privoxy</span> does not do FTP at all,
664 only HTTP and HTTPS (SSL) protocols.</p>
668 <h3 class="SECT2"><a name="DOWNLOADS2" id="DOWNLOADS2">4.22. I just
669 downloaded a Perl script, and Privoxy altered it! Yikes, what is
672 <p>Please read above.</p>
676 <h3 class="SECT2"><a name="HOSTSFILE" id="HOSTSFILE">4.23. Should I
677 continue to use a <span class="QUOTE">"HOSTS"</span> file for
678 ad-blocking?</a></h3>
680 <p>One time-tested technique to defeat common ads is to trick the local
681 DNS system by giving a phony IP address for the ad generator in the
682 local <tt class="FILENAME">HOSTS</tt> file, typically using <tt class=
683 "LITERAL">127.0.0.1</tt>, aka <tt class="LITERAL">localhost</tt>. This
684 effectively blocks the ad.</p>
686 <p>There is no reason to use this technique in conjunction with
687 <span class="APPLICATION">Privoxy</span>. <span class=
688 "APPLICATION">Privoxy</span> does essentially the same thing, much more
689 elegantly and with much more flexibility. A large <tt class=
690 "FILENAME">HOSTS</tt> file, in fact, not only duplicates effort, but
691 may get in the way and seriously slow down your system. It is
692 recommended to remove such entries from your <tt class=
693 "FILENAME">HOSTS</tt> file. If you think your hosts list is neglected
694 by <span class="APPLICATION">Privoxy's</span> configuration, consider
695 adding your list to your <tt class="FILENAME">user.action</tt>
698 <table border="0" bgcolor="#E0E0E0" width="100%">
705 ads.galore.example.com
714 <h3 class="SECT2"><a name="SEEALSO" id="SEEALSO">4.24. Where can I find
715 more information about Privoxy and related issues?</a></h3>
717 <p>Other references and sites of interest to <span class=
718 "APPLICATION">Privoxy</span> users:</p>
723 <td><a href="http://www.privoxy.org/" target=
724 "_top">http://www.privoxy.org/</a>, the <span class=
725 "APPLICATION">Privoxy</span> Home page.</td>
733 <td><a href="http://www.privoxy.org/faq/" target=
734 "_top">http://www.privoxy.org/faq/</a>, the <span class=
735 "APPLICATION">Privoxy</span> FAQ.</td>
743 <td><a href="http://www.privoxy.org/developer-manual/" target=
744 "_top">http://www.privoxy.org/developer-manual/</a>, the
745 <span class="APPLICATION">Privoxy</span> developer manual.</td>
753 <td><a href="https://sourceforge.net/projects/ijbswa/" target=
754 "_top">https://sourceforge.net/projects/ijbswa/</a>, the Project
755 Page for <span class="APPLICATION">Privoxy</span> on <a href=
756 "http://sourceforge.net" target="_top">SourceForge</a>.</td>
764 <td><a href="http://config.privoxy.org/" target=
765 "_top">http://config.privoxy.org/</a>, the web-based user
766 interface. <span class="APPLICATION">Privoxy</span> must be
767 running for this to work. Shortcut: <a href="http://p.p/" target=
768 "_top">http://p.p/</a></td>
777 "https://sourceforge.net/tracker/?group_id=11118&atid=460288"
779 "_top">https://sourceforge.net/tracker/?group_id=11118&atid=460288</a>,
780 to submit <span class="QUOTE">"misses"</span> and other
781 configuration related suggestions to the developers.</td>
789 <td><a href="http://www.squid-cache.org/" target=
790 "_top">http://www.squid-cache.org/</a>, a popular caching proxy,
791 which is often used together with <span class=
792 "APPLICATION">Privoxy</span>.</td>
801 "http://www.pps.univ-paris-diderot.fr/~jch/software/polipo/"
803 "_top">http://www.pps.univ-paris-diderot.fr/~jch/software/polipo/</a>,
804 <span class="APPLICATION">Polipo</span> is a caching proxy with
805 advanced features like pipelining, multiplexing and caching of
806 partial instances. In many setups it can be used as <span class=
807 "APPLICATION">Squid</span> replacement.</td>
815 <td><a href="https://www.torproject.org/" target=
816 "_top">https://www.torproject.org/</a>, <span class=
817 "APPLICATION">Tor</span> can help anonymize web browsing, web
818 publishing, instant messaging, IRC, SSH, and other
826 <h3 class="SECT2"><a name="MICROSUCK" id="MICROSUCK">4.25. I've noticed
827 that Privoxy changes <span class="QUOTE">"Microsoft"</span> to
828 <span class="QUOTE">"MicroSuck"</span>! Why are you manipulating my
831 <p>We're not. The text substitutions that you are seeing are disabled
832 in the default configuration as shipped. You have either manually
833 activated the <span class="QUOTE">"<tt class="LITERAL">fun</tt>"</span>
834 filter which is clearly labeled <span class="QUOTE">"Text replacements
835 for subversive browsing fun!"</span> or you are using an older Privoxy
836 version and have implicitly activated it by choosing the <span class=
837 "QUOTE">"Advanced"</span> profile in the web-based editor. Please
842 <h3 class="SECT2"><a name="VALID" id="VALID">4.26. Does Privoxy produce
843 <span class="QUOTE">"valid"</span> HTML (or XHTML)?</a></h3>
845 <p>Privoxy generates HTML in both its own <span class=
846 "QUOTE">"templates"</span>, and possibly whenever there are text
847 substitutions via a <span class="APPLICATION">Privoxy</span> filter.
848 While this should always conform to the HTML 4.01 specifications, it
849 has not been validated against this or any other standard.</p>
853 <h3 class="SECT2"><a name="SURPRISE-PRIVOXY" id=
854 "SURPRISE-PRIVOXY">4.27. How did you manage to get Privoxy on my
855 computer without my consent?</a></h3>
857 <p>We didn't. We make Privoxy available for download, but we don't go
858 around installing it on other people's systems behind their back. If
859 you discover Privoxy running on your system and are sure you didn't
860 install it yourself, somebody else did. You may not even be running the
861 real Privoxy, but maybe something else that only pretends to be
862 Privoxy, or maybe something that is based on the real Privoxy, but has
865 <p>Lately there have been reports of problems with some kind of
866 "parental control" software based on Privoxy that came preinstalled on
867 certain <a href="http://sourceforge.net/p/ijbswa/bugs/813/" target=
868 "_top">ASUS Netbooks</a>. The problems described are inconsistent with
869 the behaviour of official Privoxy versions, which suggests that the
870 preinstalled software may contain vendor modifications that we don't
871 know about and thus can't debug.</p>
873 <p>Privoxy's <a href="copyright.html">license</a> allows vendor
874 modifications, but the vendor has to comply with the license, which
875 involves informing the user about the changes and to make the changes
876 available under the same license as Privoxy itself.</p>
878 <p>If you are having trouble with a modified Privoxy version, please
879 try to talk to whoever made the modifications before reporting the
880 problem to us. Please also try to convince whoever made the
881 modifications to talk to us. If you think somebody gave you a modified
882 Privoxy version without complying to the license, please let us
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