7. Privoxy Configuration

All Privoxy configuration is stored in text files. These files can be edited with a text editor. Many important aspects of Privoxy can also be controlled easily with a web browser.

7.1. Controlling Privoxy with Your Web Browser

Privoxy's user interface can be reached through the special URL http://config.privoxy.org/ (shortcut: http://p.p/), which is a built-in page and works without Internet access. You will see the following section:

 

Privoxy Menu

        ▪  View & change the current configuration
        ▪  View the source code version numbers
        ▪  View the request headers.
        ▪  Look up which actions apply to a URL and why
        ▪  Toggle Privoxy on or off

This should be self-explanatory. Note the first item leads to an editor for the "actions list", which is where the ad, banner, cookie, and URL blocking magic is configured as well as other advanced features of Privoxy. This is an easy way to adjust various aspects of Privoxy configuration. The actions file, and other configuration files, are explained in detail below.

"Toggle Privoxy On or Off" is handy for sites that might have problems with your current actions and filters. You can in fact use it as a test to see whether it is Privoxy causing the problem or not. Privoxy continues to run as a proxy in this case, but all filtering is disabled. There is even a toggle Bookmarklet offered, so that you can toggle Privoxy with one click from your browser.

7.2. Configuration Files Overview

For Unix, *BSD and Linux, all configuration files are located in /etc/privoxy/ by default. For MS Windows, OS/2, and AmigaOS these are all in the same directory as the Privoxy executable. The name and number of configuration files has changed from previous versions, and is subject to change as development progresses.

The installed defaults provide a reasonable starting point, though some settings may be aggressive by some standards. For the time being, the principle configuration files are:

All files use the "#" character to denote a comment (the rest of the line will be ignored) angd understand line continuation through placing a backslash ("\") as the very last character in a line. If the # is preceded by a backslash, it looses its special function. Placing a # in front of an otherwise valid configuration line to prevent it from being interpreted is called "commenting out" that line.

The actions files and default.filter can use Perl style regular expressions for maximum flexibility.

After making any changes, there is no need to restart Privoxy in order for the changes to take effect. Privoxy detects such changes automatically. Note, however, that it may take one or two additional requests for the change to take effect. When changing the listening address of Privoxy, these "wake up" requests must obviously be sent to the old listening address.

While under development, the configuration content is subject to change. The below documentation may not be accurate by the time you read this. Also, what constitutes a "default" setting, may change, so please check all your configuration files on important issues.

7.3. The Main Configuration File

Again, the main configuration file is named config on Linux/Unix/BSD and OS/2, and config.txt on Windows. Configuration lines consist of an initial keyword followed by a list of values, all separated by whitespace (any number of spaces or tabs). For example:

  confdir /etc/privoxy
   

Assigns the value /etc/privoxy to the option confdir and thus indicates that the configuration directory is named "/etc/privoxy/".

All options in the config file except for confdir and logdir are optional. Watch out in the below description for what happens if you leave them unset.

The main config file controls all aspects of Privoxy's operation that are not location dependent (i.e. they apply universally, no matter where you may be surfing).

7.3.1. Configuration and Log File Locations

Privoxy can (and normally does) use a number of other files for additional configuration and logging. This section of the configuration file tells Privoxy where to find those other files.

7.3.1.1. confdir

Specifies:

The directory where the other configuration files are located

Type of value:

Path name

Default value:

/etc/privoxy (Unix) or Privoxy installation dir (Windows)

Effect if unset:

Mandatory

Notes:

No trailing "/", please

When development goes modular and multi-user, the blocker, filter, and per-user config will be stored in subdirectories of "confdir". For now, the configuration directory structure is flat, except for confdir/templates, where the HTML templates for CGI output reside (e.g. Privoxy's 404 error page).

7.3.1.2. logdir

Specifies:

The directory where all logging takes place (i.e. where logfile and jarfile are located)

Type of value:

Path name

Default value:

/var/log/privoxy (Unix) or Privoxy installation dir (Windows)

Effect if unset:

Mandatory

Notes:

No trailing "/", please

7.3.1.3. actionsfile

Specifies:

The actions file(s) to use

Type of value:

File name, relative to confdir

Default value:

  standard     # Internal purposes, recommended not editing

  default      # Main actions file

  user         # User customizations

Effect if unset:

No actions are taken at all. Simple neutral proxying.

Notes:

Multiple actionsfile lines are OK and are in fact recommended!

The default values include standard.action, which is used for internal purposes and should be loaded, default.action, which is the "main" actions file maintained by the developers, and user.action, where you can make your personal additions.

There is no point in using Privoxy without an actions file.

7.3.1.4. filterfile

Specifies:

The filter file to use

Type of value:

File name, relative to confdir

Default value:

default.filter (Unix) or default.filter.txt (Windows)

Effect if unset:

No textual content filtering takes place, i.e. all +filter{name} actions in the actions files are turned off

Notes:

The "default.filter" file contains content modification rules that use "regular expressions". These rules permit powerful changes on the content of Web pages, e.g., you could disable your favorite JavaScript annoyances, re-write the actual displayed text, or just have some fun replacing "Microsoft" with "MicroSuck" wherever it appears on a Web page.

7.3.1.5. logfile

Specifies:

The log file to use

Type of value:

File name, relative to logdir

Default value:

logfile (Unix) or privoxy.log (Windows)

Effect if unset:

No log file is used, all log messages go to the console (stderr).

Notes:

The windows version will additionally log to the console.

The logfile is where all logging and error messages are written. The level of detail and number of messages are set with the debug option (see below). The logfile can be useful for tracking down a problem with Privoxy (e.g., it's not blocking an ad you think it should block) but in most cases you probably will never look at it.

Your logfile will grow indefinitely, and you will probably want to periodically remove it. On Unix systems, you can do this with a cron job (see "man cron"). For Red Hat, a logrotate script has been included.

On SuSE Linux systems, you can place a line like "/var/log/privoxy.* +1024k 644 nobody.nogroup" in /etc/logfiles, with the effect that cron.daily will automatically archive, gzip, and empty the log, when it exceeds 1M size.

7.3.1.6. jarfile

Specifies:

The file to store intercepted cookies in

Type of value:

File name, relative to logdir

Default value:

jarfile (Unix) or privoxy.jar (Windows)

Effect if unset:

Intercepted cookies are not stored at all.

Notes:

The jarfile may grow to ridiculous sizes over time.

7.3.1.7. trustfile

Specifies:

The trust file to use

Type of value:

File name, relative to confdir

Default value:

Unset (commented out). When activated: trust (Unix) or trust.txt (Windows)

Effect if unset:

The whole trust mechanism is turned off.

Notes:

The trust mechanism is an experimental feature for building white-lists and should be used with care. It is NOT recommended for the casual user.

If you specify a trust file, Privoxy will only allow access to sites that are named in the trustfile. You can also mark sites as trusted referrers (with +), with the effect that access to untrusted sites will be granted, if a link from a trusted referrer was used. The link target will then be added to the "trustfile". Possible applications include limiting Internet access for children.

If you use + operator in the trust file, it may grow considerably over time.

7.3.2. Local Set-up Documentation

If you intend to operate Privoxy for more users that just yourself, it might be a good idea to let them know how to reach you, what you block and why you do that, your policies etc.

7.3.2.1. trust-info-url

Specifies:

A URL to be displayed in the error page that users will see if access to an untrusted page is denied.

Type of value:

URL

Default value:

Two example URL are provided

Effect if unset:

No links are displayed on the "untrusted" error page.

Notes:

The value of this option only matters if the experimental trust mechanism has been activated. (See trustfile above.)

If you use the trust mechanism, it is a good idea to write up some on-line documentation about your trust policy and to specify the URL(s) here. Use multiple times for multiple URLs.

The URL(s) should be added to the trustfile as well, so users don't end up locked out from the information on why they were locked out in the first place!

7.3.2.2. admin-address

Specifies:

An email address to reach the proxy administrator.

Type of value:

Email address

Default value:

Unset

Effect if unset:

No email address is displayed on error pages and the CGI user interface.

Notes:

If both admin-address and proxy-info-url are unset, the whole "Local Privoxy Support" box on all generated pages will not be shown.

7.3.2.3. proxy-info-url

Specifies:

A URL to documentation about the local Privoxy setup, configuration or policies.

Type of value:

URL

Default value:

Unset

Effect if unset:

No link to local documentation is displayed on error pages and the CGI user interface.

Notes:

If both admin-address and proxy-info-url are unset, the whole "Local Privoxy Support" box on all generated pages will not be shown.

This URL shouldn't be blocked ;-)

7.3.3. Debugging

These options are mainly useful when tracing a problem. Note that you might also want to invoke Privoxy with the --no-daemon command line option when debugging.

7.3.3.1. debug

Specifies:

Key values that determine what information gets logged.

Type of value:

Integer values

Default value:

12289 (i.e.: URLs plus informational and warning messages)

Effect if unset:

Nothing gets logged.

Notes:

The available debug levels are:

  debug         1 # show each GET/POST/CONNECT request
  debug         2 # show each connection status
  debug         4 # show I/O status
  debug         8 # show header parsing
  debug        16 # log all data into the logfile
  debug        32 # debug force feature
  debug        64 # debug regular expression filter 
  debug       128 # debug fast redirects
  debug       256 # debug GIF de-animation
  debug       512 # Common Log Format
  debug      1024 # debug kill pop-ups
  debug      4096 # Startup banner and warnings.
  debug      8192 # Non-fatal errors

To select multiple debug levels, you can either add them or use multiple debug lines.

A debug level of 1 is informative because it will show you each request as it happens. 1, 4096 and 8192 are highly recommended so that you will notice when things go wrong. The other levels are probably only of interest if you are hunting down a specific problem. They can produce a hell of an output (especially 16).

The reporting of fatal errors (i.e. ones which crash Privoxy) is always on and cannot be disabled.

If you want to use CLF (Common Log Format), you should set "debug 512" ONLY and not enable anything else.

7.3.3.2. single-threaded

Specifies:

Whether to run only one server thread

Type of value:

None

Default value:

Unset

Effect if unset:

Multi-threaded (or, where unavailable: forked) operation, i.e. the ability to serve multiple requests simultaneously.

Notes:

This option is only there for debug purposes and you should never need to use it. It will drastically reduce performance.

7.3.4. Access Control and Security

This section of the config file controls the security-relevant aspects of Privoxy's configuration.

7.3.4.1. listen-address

Specifies:

The IP address and TCP port on which Privoxy will listen for client requests.

Type of value:

[IP-Address]:Port

Default value:

localhost:8118

Effect if unset:

Bind to localhost (127.0.0.1), port 8118. This is suitable and recommended for home users who run Privoxy on the same machine as their browser.

Notes:

You will need to configure your browser(s) to this proxy address and port.

If you already have another service running on port 8118, or if you want to serve requests from other machines (e.g. on your local network) as well, you will need to override the default.

If you leave out the IP address, Privoxy will bind to all interfaces (addresses) on your machine and may become reachable from the Internet. In that case, consider using access control lists (ACL's) (see "ACLs" below), or a firewall.

Example:

Suppose you are running Privoxy on a machine which has the address 192.168.0.1 on your local private network (192.168.0.0) and has another outside connection with a different address. You want it to serve requests from inside only:

  listen-address  192.168.0.1:8118

7.3.4.2. toggle

Specifies:

Initial state of "toggle" status

Type of value:

1 or 0

Default value:

1

Effect if unset:

Act as if toggled on

Notes:

If set to 0, Privoxy will start in "toggled off" mode, i.e. behave like a normal, content-neutral proxy. See enable-remote-toggle below. This is not really useful anymore, since toggling is much easier via the web interface then via editing the conf file.

The windows version will only display the toggle icon in the system tray if this option is present.

7.3.4.3. enable-remote-toggle

Specifies:

Whether or not the web-based toggle feature may be used

Type of value:

0 or 1

Default value:

1

Effect if unset:

The web-based toggle feature is disabled.

Notes:

When toggled off, Privoxy acts like a normal, content-neutral proxy, i.e. it acts as if none of the actions applied to any URL.

For the time being, access to the toggle feature can not be controlled separately by "ACLs" or HTTP authentication, so that everybody who can access Privoxy (see "ACLs" and listen-address above) can toggle it for all users. So this option is not recommended for multi-user environments with untrusted users.

Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect.

7.3.4.4. enable-edit-actions

Specifies:

Whether or not the web-based actions file editor may be used

Type of value:

0 or 1

Default value:

1

Effect if unset:

The web-based actions file editor is disabled.

Notes:

For the time being, access to the editor can not be controlled separately by "ACLs" or HTTP authentication, so that everybody who can access Privoxy (see "ACLs" and listen-address above) can modify its configuration for all users. So this option is not recommended for multi-user environments with untrusted users.

Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect.

7.3.4.5. ACLs: permit-access and deny-access

Specifies:

Who can access what.

Type of value:

src_addr[/src_masklen] [dst_addr[/dst_masklen]]

Where src_addr and dst_addr are IP addresses in dotted decimal notation or valid DNS names, and src_masklen and dst_masklen are subnet masks in CIDR notation, i.e. integer values from 2 to 30 representing the length (in bits) of the network address. The masks and the whole destination part are optional.

Default value:

Unset

Effect if unset:

Don't restrict access further than implied by listen-address

Notes:

Access controls are included at the request of ISPs and systems administrators, and are not usually needed by individual users. For a typical home user, it will normally suffice to ensure that Privoxy only listens on the localhost or internal (home) network address by means of the listen-address option.

Please see the warnings in the FAQ that this proxy is not intended to be a substitute for a firewall or to encourage anyone to defer addressing basic security weaknesses.

Multiple ACL lines are OK. If any ACLs are specified, then the Privoxy talks only to IP addresses that match at least one permit-access line and don't match any subsequent deny-access line. In other words, the last match wins, with the default being deny-access.

If Privoxy is using a forwarder (see forward below) for a particular destination URL, the dst_addr that is examined is the address of the forwarder and NOT the address of the ultimate target. This is necessary because it may be impossible for the local Privoxy to determine the IP address of the ultimate target (that's often what gateways are used for).

You should prefer using IP addresses over DNS names, because the address lookups take time. All DNS names must resolve! You can not use domain patterns like "*.org" or partial domain names. If a DNS name resolves to multiple IP addresses, only the first one is used.

Denying access to particular sites by ACL may have undesired side effects if the site in question is hosted on a machine which also hosts other sites.

Examples:

Explicitly define the default behavior if no ACL and listen-address are set: "localhost" is OK. The absence of a dst_addr implies that all destination addresses are OK:

  permit-access  localhost

Allow any host on the same class C subnet as www.privoxy.org access to nothing but www.example.com:

  permit-access  www.privoxy.org/24 www.example.com/32

Allow access from any host on the 26-bit subnet 192.168.45.64 to anywhere, with the exception that 192.168.45.73 may not access www.dirty-stuff.example.com:

  permit-access  192.168.45.64/26
  deny-access    192.168.45.73    www.dirty-stuff.example.com

7.3.4.6. buffer-limit

Specifies:

Maximum size of the buffer for content filtering.

Type of value:

Size in Kbytes

Default value:

4096

Effect if unset:

Use a 4MB (4096 KB) limit.

Notes:

For content filtering, i.e. the +filter and +deanimate-gif actions, it is necessary that Privoxy buffers the entire document body. This can be potentially dangerous, since a server could just keep sending data indefinitely and wait for your RAM to exhaust -- with nasty consequences. Hence this option.

When a document buffer size reaches the buffer-limit, it is flushed to the client unfiltered and no further attempt to filter the rest of the document is made. Remember that there may be multiple threads running, which might require up to buffer-limit Kbytes each, unless you have enabled "single-threaded" above.

7.3.5. Forwarding

This feature allows routing of HTTP requests through a chain of multiple proxies. It can be used to better protect privacy and confidentiality when accessing specific domains by routing requests to those domains through an anonymous public proxy (see e.g. http://www.multiproxy.org/anon_list.htm) Or to use a caching proxy to speed up browsing. Or chaining to a parent proxy may be necessary because the machine that Privoxy runs on has no direct Internet access.

Also specified here are SOCKS proxies. Privoxy supports the SOCKS 4 and SOCKS 4A protocols.

7.3.5.1. forward

Specifies:

To which parent HTTP proxy specific requests should be routed.

Type of value:

target_domain[:port] http_parent[/port]

Where target_domain is a domain name pattern (see the chapter on domain matching in the default.action file), http_parent is the address of the parent HTTP proxy as an IP addresses in dotted decimal notation or as a valid DNS name (or "." to denote "no forwarding", and the optional port parameters are TCP ports, i.e. integer values from 1 to 64535

Default value:

Unset

Effect if unset:

Don't use parent HTTP proxies.

Notes:

If http_parent is ".", then requests are not forwarded to another HTTP proxy but are made directly to the web servers.

Multiple lines are OK, they are checked in sequence, and the last match wins.

Examples:

Everything goes to an example anonymizing proxy, except SSL on port 443 (which it doesn't handle):

  forward   .*     anon-proxy.example.org:8080
  forward   :443   .

Everything goes to our example ISP's caching proxy, except for requests to that ISP's sites:

  forward   .*.                caching-proxy.example-isp.net:8000
  forward   .example-isp.net   .

7.3.5.2. forward-socks4 and forward-socks4a

Specifies:

Through which SOCKS proxy (and to which parent HTTP proxy) specific requests should be routed.

Type of value:

target_domain[:port] socks_proxy[/port] http_parent[/port]

Where target_domain is a domain name pattern (see the chapter on domain matching in the default.action file), http_parent and socks_proxy are IP addresses in dotted decimal notation or valid DNS names (http_parent may be "." to denote "no HTTP forwarding"), and the optional port parameters are TCP ports, i.e. integer values from 1 to 64535

Default value:

Unset

Effect if unset:

Don't use SOCKS proxies.

Notes:

Multiple lines are OK, they are checked in sequence, and the last match wins.

The difference between forward-socks4 and forward-socks4a is that in the SOCKS 4A protocol, the DNS resolution of the target hostname happens on the SOCKS server, while in SOCKS 4 it happens locally.

If http_parent is ".", then requests are not forwarded to another HTTP proxy but are made (HTTP-wise) directly to the web servers, albeit through a SOCKS proxy.

Examples:

From the company example.com, direct connections are made to all "internal" domains, but everything outbound goes through their ISP's proxy by way of example.com's corporate SOCKS 4A gateway to the Internet.

  forward-socks4a   .*.            socks-gw.example.com:1080  www-cache.example-isp.net:8080
  forward           .example.com   .

A rule that uses a SOCKS 4 gateway for all destinations but no HTTP parent looks like this:

  forward-socks4   .*.            socks-gw.example.com:1080  .

7.3.5.3. Advanced Forwarding Examples

If you have links to multiple ISPs that provide various special content only to their subscribers, you can configure multiple Privoxies which have connections to the respective ISPs to act as forwarders to each other, so that your users can see the internal content of all ISPs.

Assume that host-a has a PPP connection to isp-a.net. And host-b has a PPP connection to isp-b.net. Both run Privoxy. Their forwarding configuration can look like this:

host-a:

  forward    .*.         .
  forward    .isp-b.net  host-b:8118

host-b:

  forward    .*.         .
  forward    .isp-a.net  host-a:8118

Now, your users can set their browser's proxy to use either host-a or host-b and be able to browse the internal content of both isp-a and isp-b.

If you intend to chain Privoxy and squid locally, then chain as browser -> squid -> privoxy is the recommended way.

Assuming that Privoxy and squid run on the same box, your squid configuration could then look like this:

  # Define Privoxy as parent proxy (without ICP) 
  cache_peer 127.0.0.1 parent 8118 7 no-query 

  # Define ACL for protocol FTP 
  acl ftp proto FTP 

  # Do not forward FTP requests to Privoxy
  always_direct allow ftp 

  # Forward all the rest to Privoxy
  never_direct allow all

You would then need to change your browser's proxy settings to squid's address and port. Squid normally uses port 3128. If unsure consult http_port in squid.conf.

7.3.6. Windows GUI Options

Privoxy has a number of options specific to the Windows GUI interface:

If "activity-animation" is set to 1, the Privoxy icon will animate when "Privoxy" is active. To turn off, set to 0.

  activity-animation 1
   

If "log-messages" is set to 1, Privoxy will log messages to the console window:

  log-messages 1
   

If "log-buffer-size" is set to 1, the size of the log buffer, i.e. the amount of memory used for the log messages displayed in the console window, will be limited to "log-max-lines" (see below).

Warning: Setting this to 0 will result in the buffer to grow infinitely and eat up all your memory!

  log-buffer-size 1
   

log-max-lines is the maximum number of lines held in the log buffer. See above.

  log-max-lines 200
   

If "log-highlight-messages" is set to 1, Privoxy will highlight portions of the log messages with a bold-faced font:

  log-highlight-messages 1
   

The font used in the console window:

  log-font-name Comic Sans MS
   

Font size used in the console window:

  log-font-size 8
   

"show-on-task-bar" controls whether or not Privoxy will appear as a button on the Task bar when minimized:

  show-on-task-bar 0
   

If "close-button-minimizes" is set to 1, the Windows close button will minimize Privoxy instead of closing the program (close with the exit option on the File menu).

  close-button-minimizes 1
   

The "hide-console" option is specific to the MS-Win console version of Privoxy. If this option is used, Privoxy will disconnect from and hide the command console.

  #hide-console
   

7.4. Actions Files

The actions files are used to define what actions Privoxy takes for which URLs, and thus determines how ad images, cookies and various other aspects of HTTP content and transactions are handled, and on which sites (or even parts thereof). There are three such files included with Privoxy, with slightly different purposes. default.action sets the default policies. standard.action is used by Privoxy and the web based editor to set pre-defined values (and normally should not be edited). Local exceptions are best done in user.action. The content of these can all be viewed and edited from http://config.privoxy.org/show-status.

Anything you want can blocked, including ads, banners, or just some obnoxious URL that you would rather not see is done here. Cookies can be accepted or rejected, or accepted only during the current browser session (i.e. not written to disk), content can be modified, JavaScripts tamed, user-tracking fooled, and much more. See below for a complete list of available actions.

An actions file typically has sections. Near the top, "aliases" are optionally defined (discussed below), then the default set of rules which will apply universally to all sites and pages. And then below that, exceptions to the defined universal policies.

7.4.1. Finding the Right Mix

Note that some actions like cookie suppression or script disabling may render some sites unusable, which rely on these techniques to work properly. Finding the right mix of actions is not easy and certainly a matter of personal taste. In general, it can be said that the more "aggressive" your default settings (in the top section of the actions file) are, the more exceptions for "trusted" sites you will have to make later. If, for example, you want to kill popup windows per default, you'll have to make exceptions from that rule for sites that you regularly use and that require popups for actually useful content, like maybe your bank, favorite shop, or newspaper.

We have tried to provide you with reasonable rules to start from in the distribution actions files. But there is no general rule of thumb on these things. There just are too many variables, and sites are constantly changing. Sooner or later you will want to change the rules (and read this chapter again :).

7.4.2. How to Edit

The easiest way to edit the "actions" files is with a browser by using our browser-based editor, which can be reached from http://config.privoxy.org/show-status.

If you prefer plain text editing to GUIs, you can of course also directly edit the the actions files.

7.4.3. How Actions are Applied to URLs

Actions files are divided into sections. There are special sections, like the "alias" sections which will be discussed later. For now let's concentrate on regular sections: They have a heading line (often split up to multiple lines for readability) which consist of a list of actions, separated by whitespace and enclosed in curly braces. Below that, there is a list of URL patterns, each on a separate line.

To determine which actions apply to a request, the URL of the request is compared to all patterns in this file. Every time it matches, the list of applicable actions for the URL is incrementally updated, using the heading of the section in which the pattern is located. If multiple matches for the same URL set the same action differently, the last match wins. If not, the effects are aggregated (e.g. a URL might match both the "+handle-as-image" and "+block" actions).

You can trace this process by visiting http://config.privoxy.org/show-url-info.

More detail on this is provided in the Appendix, Anatomy of an Action.

7.4.4. Patterns

Generally, a pattern has the form <domain>/<path>, where both the <domain> and <path> are optional. (This is why the pattern / matches all URLs).

www.example.com/

is a domain-only pattern and will match any request to www.example.com, regardless of which document on that server is requested.

www.example.com

means exactly the same. For domain-only patterns, the trailing / may be omitted.

www.example.com/index.html

matches only the single document /index.html on www.example.com.

/index.html

matches the document /index.html, regardless of the domain, i.e. on any web server.

index.html

matches nothing, since it would be interpreted as a domain name and there is no top-level domain called .html.

7.4.4.1. The Domain Pattern

The matching of the domain part offers some flexible options: if the domain starts or ends with a dot, it becomes unanchored at that end. For example:

.example.com

matches any domain that ENDS in .example.com

www.

matches any domain that STARTS with www.

.example.

matches any domain that CONTAINS .example. (Correctly speaking: It matches any FQDN that contains example as a domain.)

Additionally, there are wild-cards that you can use in the domain names themselves. They work pretty similar to shell wild-cards: "*" stands for zero or more arbitrary characters, "?" stands for any single character, you can define character classes in square brackets and all of that can be freely mixed:

ad*.example.com

matches "adserver.example.com", "ads.example.com", etc but not "sfads.example.com"

*ad*.example.com

matches all of the above, and then some.

.?pix.com

matches www.ipix.com, pictures.epix.com, a.b.c.d.e.upix.com etc.

www[1-9a-ez].example.c*

matches www1.example.com, www4.example.cc, wwwd.example.cy, wwwz.example.com etc., but not wwww.example.com.

7.4.4.2. The Path Pattern

Privoxy uses Perl compatible regular expressions (through the PCRE library) for matching the path.

There is an Appendix with a brief quick-start into regular expressions, and full (very technical) documentation on PCRE regex syntax is available on-line at http://www.pcre.org/man.txt. You might also find the Perl man page on regular expressions (man perlre) useful, which is available on-line at http://www.perldoc.com/perl5.6/pod/perlre.html.

Note that the path pattern is automatically left-anchored at the "/", i.e. it matches as if it would start with a "^" (regular expression speak for the beginning of a line).

Please also note that matching in the path is case INSENSITIVE by default, but you can switch to case sensitive at any point in the pattern by using the "(?-i)" switch: www.example.com/(?-i)PaTtErN.* will match only documents whose path starts with PaTtErN in exactly this capitalization.

7.4.5. Actions

All actions are disabled by default, until they are explicitly enabled somewhere in an actions file. Actions are turned on if preceded with a "+", and turned off if preceded with a "-". So a "+action" means "do that action", e.g. "+block" means please "block the following URL patterns".

Actions are invoked by enclosing the action name in curly braces (e.g. {+some_action}), followed by a list of URLs (or patterns that match URLs) to which the action applies. There are three classes of actions:

  • Boolean, i.e the action can only be "on" or "off". Examples:

      {+name}        # enable this action
      {-name}        # disable this action
         

  • Parameterized, e.g. "+/-hide-user-agent{ Mozilla 1.0 }", where some value is required in order to enable this type of action. Examples:

      {+name{param}}  # enable action and set parameter to "param"
      {-name}         # disable action ("parameter") can be omitted
         

  • Multi-value, e.g. "{+/-add-header{Name: value}}" or "{+/-send-wafer{name=value}}"), where some value needs to be defined in addition to simply enabling the action. Examples:

      {+name{param=value}}   # enable action and set "param" to "value"
      {-name{param=value}}   # remove the parameter "param" completely
      {-name}                # disable this action totally and remove param too
         

If nothing is specified in any actions file, no "actions" are taken. So in this case Privoxy would just be a normal, non-blocking, non-anonymizing proxy. You must specifically enable the privacy and blocking features you need (although the provided default actions files will give a good starting point).

Later defined actions always over-ride earlier ones. So exceptions to any rules you make, should come in the latter part of the file. For multi-valued actions, the actions are applied in the order they are specified. Actions files are processed in the order they are defined in config (the default installation has three actions files). It also quite possible for any given URL pattern to match more than one action!

The list of valid Privoxy "actions" are:

7.4.5.1. +add-header{Name: value}

Type:

Multi-value.

Typical uses:

Send a user defined HTTP header to the web server.

Possible values:

Any value is possible. Validity of the defined HTTP headers is not checked.

Example usage:

     {+add-header{X-User-Tracking: sucks}}
     .example.com
    

Notes:

This action may be specified multiple times, in order to define multiple headers. This is rarely needed for the typical user. If you don't know what "HTTP headers" are, you definitely don't need to worry about this one.

7.4.5.2. +block

Type:

Boolean.

Typical uses:

Used to block a URL from reaching your browser. The URL may be anything, but is typically used to block ads or other obnoxious content.

Possible values:

N/A

Example usage:

     {+block}
     .banners.example.com
     .ads.r.us
    

Notes:

If a URL matches one of the blocked patterns, Privoxy will intercept the URL and display its special "BLOCKED" page instead. If there is sufficient space, a large red banner will appear with a friendly message about why the page was blocked, and a way to go there anyway. If there is insufficient space a smaller blocked page will appear without the red banner. Click here to view the default blocked HTML page (Privoxy must be running for this to work as intended!).

A very important exception is if the URL matches both "+block" and "+handle-as-image", then it will be handled by "+set-image-blocker" (see below). It is important to understand this process, in order to understand how Privoxy is able to deal with ads and other objectionable content.

The "+filter" action can also perform some of the same functionality as "+block", but by virtue of very different programming techniques, and is most often used for different reasons.

7.4.5.3. +deanimate-gifs

Type:

Parameterized.

Typical uses:

To stop those annoying, distracting animated GIF images.

Possible values:

"last" or "first"

Example usage:

      {+deanimate-gifs{last}}
      .example.com
    

Notes:

De-animate all animated GIF images, i.e. reduce them to their last frame. This will also shrink the images considerably (in bytes, not pixels!). If the option "first" is given, the first frame of the animation is used as the replacement. If "last" is given, the last frame of the animation is used instead, which probably makes more sense for most banner animations, but also has the risk of not showing the entire last frame (if it is only a delta to an earlier frame).

7.4.5.4. +downgrade-http-version

Type:

Boolean.

Typical uses:

"+downgrade-http-version" will downgrade HTTP/1.1 client requests to HTTP/1.0 and downgrade the responses as well.

Possible values:

N/A

Example usage:

     {+downgrade-http-version}
     .example.com
    

Notes:

Use this action for servers that use HTTP/1.1 protocol features that Privoxy doesn't handle well yet. HTTP/1.1 is only partially implemented. Default is not to downgrade requests. This is an infrequently needed action, and is used to help with rare problem sites only.

7.4.5.5. +fast-redirects

Type:

Boolean.

Typical uses:

The "+fast-redirects" action enables interception of "redirect" requests from one server to another, which are used to track users.Privoxy can cut off all but the last valid URL in a redirect request and send a local redirect back to your browser without contacting the intermediate site(s).

Possible values:

N/A

Example usage:

     {+fast-redirects}
     .example.com
    

Notes:

Many sites, like yahoo.com, don't just link to other sites. Instead, they will link to some script on their own server, giving the destination as a parameter, which will then redirect you to the final target. URLs resulting from this scheme typically look like: http://some.place/some_script?http://some.where-else.

Sometimes, there are even multiple consecutive redirects encoded in the URL. These redirections via scripts make your web browsing more traceable, since the server from which you follow such a link can see where you go to. Apart from that, valuable bandwidth and time is wasted, while your browser ask the server for one redirect after the other. Plus, it feeds the advertisers.

This is a normally "on" feature, and often requires exceptions for sites that are sensitive to defeating this mechanism.

7.4.5.6. +filter

Type:

Parameterized.

Typical uses:

Apply page filtering as defined by named sections of the default.filter file to the specified site(s). "Filtering" can be any modification of the raw page content, including re-writing or deletion of content.

Possible values:

"+filter" must include the name of one of the section identifiers from default.filter (or whatever filterfile is specified in config).

Example usage (from the current default.filter):

+filter{html-annoyances}: Get rid of particularly annoying HTML abuse.

+filter{js-annoyances}: Get rid of particularly annoying JavaScript abuse

+filter{content-cookies}: Kill cookies that come in the HTML or JS content

+filter{popups}: Kill all popups in JS and HTML

+filter{frameset-borders}: Give frames a border and make them resizable

+filter{webbugs}: Squish WebBugs (1x1 invisible GIFs used for user tracking)

+filter{refresh-tags}: Kill automatic refresh tags (for dial-on-demand setups)

+filter{fun}: Text replacements for subversive browsing fun!

+filter{nimda}: Remove Nimda (virus) code.

+filter{banners-by-size}: Kill banners by size (very efficient!)

+filter{shockwave-flash}: Kill embedded Shockwave Flash objects

+filter{crude-parental}: Kill all web pages that contain the words "sex" or "warez"

Notes:

This is potentially a very powerful feature! And requires a knowledge of regular expressions if you want to "roll your own". Filtering operates on a line by line basis throughout the entire page.

Filtering requires buffering the page content, which may appear to slow down page rendering since nothing is displayed until all content has passed the filters. (It does not really take longer, but seems that way since the page is not incrementally displayed.) This effect will be more noticeable on slower connections.

Filtering can achieve some of the effects as the "+block" action, i.e. it can be used to block ads and banners. In the overall scheme of things, filtering is one of the first things "Privoxy" does with a web page. So other most other actions are applied to the already "filtered" page.

7.4.5.7. +hide-forwarded-for-headers

Type:

Boolean.

Typical uses:

Block any existing X-Forwarded-for HTTP header, and do not add a new one.

Possible values:

N/A

Example usage:

     {+hide-forwarded-for-headers}
     .example.com
    

Notes:

It is fairly safe to leave this on. It does not seem to break many sites.

7.4.5.8. +hide-from-header

Type:

Parameterized.

Typical uses:

To block the browser from sending your email address in a "From:" header.

Possible values:

Keyword: "block", or any user defined value.

Example usage:

     {+hide-from-header{block}}
     .example.com
    

Notes:

The keyword "block" will completely remove the header (not to be confused with the "+block" action). Alternately, you can specify any value you prefer to send to the web server.

7.4.5.9. +hide-referer

Type:

Parameterized.

Typical uses:

Don't send the "Referer:" (sic) HTTP header to the web site. Or, alternately send a forged header instead.

Possible values:

Prevent the header from being sent with the keyword, "block". Or, "forge" a URL to one from the same server as the request. Or, set to user defined value of your choice.

Example usage:

     {+hide-referer{forge}}
     .example.com
    

Notes:

"forge" is the preferred option here, since some servers will not send images back otherwise.

"+hide-referrer" is an alternate spelling of "+hide-referer". It has the exact same parameters, and can be freely mixed with, "+hide-referer". ("referrer" is the correct English spelling, however the HTTP specification has a bug - it requires it to be spelled as "referer".)

7.4.5.10. +hide-user-agent

Type:

Parameterized.

Typical uses:

To change the "User-Agent:" header so web servers can't tell your browser type. Who's business is it anyway?

Possible values:

Any user defined string.

Example usage:

     {+hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)}}
     .msn.com
    

Notes:

Warning! This breaks many web sites that depend on this in order to determine how the target browser will respond to various requests. Use with caution.

7.4.5.11. +handle-as-image

Type:

Boolean.

Typical uses:

To define what Privoxy should treat automatically as an image, and is an important ingredient of how ads are handled.

Possible values:

N/A

Example usage:

     {+handle-as-image}
     /.*\.(gif|jpg|jpeg|png|bmp|ico)
    

Notes:

This only has meaning if the URL (or pattern) also is "+block"ed, in which case a user definable image can be sent rather than a HTML page. This is integral to the whole concept of ad blocking: the URL must match both a "+block" rule, and "+handle-as-image". (See "+set-image-blocker" below for control over what will actually be displayed by the browser.)

There is little reason to change the default definition for this action.

7.4.5.12. +set-image-blocker

Type:

Parameterized.

Typical uses:

Decide what to do with URLs that end up tagged with both "+block" and "+handle-as-image", e.g an advertisement.

Possible values:

There are four available options: "-set-image-blocker" will send a HTML "blocked" page, usually resulting in a "broken image" icon. "+set-image-blocker{blank}" will send a 1x1 transparent GIF image. "+set-image-blocker{pattern}" will send a checkerboard type pattern (the default). And finally, "+set-image-blocker{http://xyz.com}" will send a HTTP temporary redirect to the specified image. This has the advantage of the icon being being cached by the browser, which will speed up the display.

Example usage:

     {+set-image-blocker{blank}}
     .example.com
    

Notes:

If you want invisible ads, they need to meet criteria as matching both images and blocked actions. And then, "image-blocker" should be set to "blank" for invisibility. Note you cannot treat HTML pages as images in most cases. For instance, frames require an HTML page to display. So a frame that is an ad, typically cannot be treated as an image. Forcing an "image" in this situation just will not work reliably.

7.4.5.13. +limit-connect

Type:

Parameterized.

Typical uses:

By default, Privoxy only allows HTTP CONNECT requests to port 443 (the standard, secure HTTPS port). Use "+limit-connect" to disable this altogether, or to allow more ports.

Possible values:

Any valid port number, or port number range.

Example usages:

     +limit-connect{443}                       # This is the default and need not be specified.
     +limit-connect{80,443}                  # Ports 80 and 443 are OK.
     +limit-connect{-3, 7, 20-100, 500-}   # Port less than 3, 7, 20 to 100 and above 500 are OK.
    

Notes:

The CONNECT methods exists in HTTP to allow access to secure websites (https:// URLs) through proxies. It works very simply: the proxy connects to the server on the specified port, and then short-circuits its connections to the client and to the remote proxy. This can be a big security hole, since CONNECT-enabled proxies can be abused as TCP relays very easily.

If you want to allow CONNECT for more ports than this, or want to forbid CONNECT altogether, you can specify a comma separated list of ports and port ranges (the latter using dashes, with the minimum defaulting to 0 and max to 65K).

If you don't know what any of this means, there probably is no reason to change this one.

7.4.5.14. +prevent-compression

Type:

Boolean.

Typical uses:

Prevent the specified websites from compressing HTTP data.

Possible values:

N/A

Example usage:

     {+prevent-compression}
     .example.com
    

Notes:

Some websites do this, which can be a problem for Privoxy, since "+filter", "+kill-popups" and "+gif-deanimate" will not work on compressed data. This will slow down connections to those websites, though. Default typically is to turn "prevent-compression" on.

7.4.5.15. +session-cookies-only

Type:

Boolean.

Typical uses:

Allow cookies for the current browser session only.

Possible values:

N/A

Example usage (disabling):

     {-session-cookies-only}
     .example.com
    

Notes:

If websites set cookies, "+session-cookies-only" will make sure they are erased when you exit and restart your web browser. This makes profiling cookies useless, but won't break sites which require cookies so that you can log in for transactions. This is generally turned on for all sites, and is the recommended setting.

"+prevent-*-cookies" actions should be turned off as well (see below), for "+session-cookies-only" to work. Or, else no cookies will get through at all. For, "persistent" cookies that survive across browser sessions, see below as well.

7.4.5.16. +prevent-reading-cookies

Type:

Boolean.

Typical uses:

Explicitly prevent the web server from reading any cookies on your system.

Possible values:

N/A

Example usage:

     {+prevent-reading-cookies}
     .example.com
    

Notes:

Often used in conjunction with "+prevent-setting-cookies" to disable cookies completely. Note that "+session-cookies-only" requires these to both be disabled (or else it never gets any cookies to cache).

For "persistent" cookies to work (i.e. they survive across browser sessions and reboots), all three cookie settings should be "off" for the specified sites.

7.4.5.17. +prevent-setting-cookies

Type:

Boolean.

Typical uses:

Explicitly block the web server from storing cookies on your system.

Possible values:

N/A

Example usage:

     {+prevent-setting-cookies}
     .example.com
    

Notes:

Often used in conjunction with "+prevent-reading-cookies" to disable cookies completely (see above).

7.4.5.18. +kill-popups

Type:

Boolean.

Typical uses:

Stop those annoying JavaScript pop-up windows!

Possible values:

N/A

Example usage:

     {+kill-popups}
     .example.com
    

Notes:

"+kill-popups" uses a built in filter to disable pop-ups that use the window.open() function, etc. This is one of the first actions processed by Privoxy as it contacts the remote web server. This action is not always 100% reliable, and is supplemented by "+filter{popups}".

7.4.5.19. +send-vanilla-wafer

Type:

Boolean.

Typical uses:

Sends a cookie for every site stating that you do not accept any copyright on cookies sent to you, and asking them not to track you.

Possible values:

N/A

Example usage:

     {+send-vanilla-wafer}
     .example.com
    

Notes:

This action only applies if you are using a jarfile for saving cookies. Of course, this is a (relatively) unique header and could conceivably be used to track you.

7.4.5.20. +send-wafer

Type:

Multi-value.

Typical uses:

This allows you to send an arbitrary, user definable cookie.

Possible values:

User specified cookie name and corresponding value.

Example usage:

     {+send-wafer{name=value}}
     .example.com
    

Notes:

This can be specified multiple times in order to add as many cookies as you like.

7.4.5.21. Actions Examples

Note that the meaning of any of the above examples is reversed by preceding the action with a "-", in place of the "+". Also, that some actions are turned on in the default section of the actions file, and require little to no additional configuration. These are just "on". But, other actions that are turned on the default section do typically require exceptions to be listed in the lower sections of actions file. E.g. by default no URLs are "blocked" (i.e. in the default definitions of default.action). We need exceptions to this in order to enable ad blocking.

Some examples:

Turn off cookies by default, then allow a few through for specified sites (showing an excerpt from the "default" section of an actions file ONLY):

 # Excerpt only:
 # Allow cookies to and from the server, but
 # for this browser session ONLY
 { 
   # other actions normally listed here...
   -prevent-setting-cookies \
   -prevent-reading-cookies \
   +session-cookies-only   \  
 }
 / # match all URLs

 # Exceptions to the above, sites that benefit from persistent cookies
 # that are saved from one browser session to the next.
 { -session-cookies-only }
  .javasoft.com
  .sun.com
  .yahoo.com
  .msdn.microsoft.com
  .redhat.com

   

Now turn off "fast redirects", and then we allow two exceptions:

 # Turn them off (excerpt only)!
 {
  # other actions normally listed here...
  +fast-redirects
 }
 / # match all URLs
 
 # Reverse it for these two sites, which don't work right without it.
 {-fast-redirects}
  www.ukc.ac.uk/cgi-bin/wac\.cgi\?
  login.yahoo.com
   

Turn on page filtering according to rules in the defined sections of default.filter, and make one exception for Sourceforge:

 # Run everything through the filter file, using only certain
 # specified sections:
 {
  # other actions normally listed here...
  +filter{html-annoyances} +filter{js-annoyances} +filter{kill-popups}\
  +filter{webbugs} +filter{nimda} +filter{banners-by-size}
 }
 / #match all URLs
              
 # Then disable filtering of code from all sourceforge domains!
 {-filter}
  .sourceforge.net
   

Now some URLs that we want "blocked" (normally generates the "blocked" banner). Typically, the "block" action is off by default in the upper section of an actions file, then enabled against certain URLs and patterns in the lower part of the file. Many of these use regular expressions that will expand to match multiple URLs:

  # Blocklist:
  {+block}
  ad*.
  .*ads.
  banner?.
  count*.
  /.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?)
  /(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/
  .hitbox.com 
  /.*/(ng)?adclient\.cgi
  /.*/(plain|live|rotate)[-_.]?ads?/
  /.*/abanners/
  /autoads/
   

Note that many of these actions have the potential to cause a page to misbehave, possibly even not to display at all. There are many ways a site designer may choose to design his site, and what HTTP header content, and other criteria, he may depend on. There is no way to have hard and fast rules for all sites. See the Appendix for a brief example on troubleshooting actions.

7.4.6. Aliases

Custom "actions", known to Privoxy as "aliases", can be defined by combining other "actions". These can in turn be invoked just like the built-in "actions". Currently, an alias can contain any character except space, tab, "=", "{" or "}". But please use only "a"- "z", "0"-"9", "+", and "-". Alias names are not case sensitive, and must be defined before other actions in the actions file! And there can only be one set of "aliases" defined per file. Each actions file may have its own aliases, but they are only visible within that file.

Now let's define a few aliases:

 # Useful custom aliases we can use later. These must come first!
 {{alias}}
 +prevent-cookies = +prevent-setting-cookies +prevent-reading-cookies
 -prevent-cookies = -prevent-setting-cookies -prevent-reading-cookies
 fragile     = -block -prevent-cookies -filter -fast-redirects -hide-referer -kill-popups
 shop        = -prevent-cookies -filter -fast-redirects
 +imageblock = +block +handle-as-image

 # Aliases defined from other aliases, for people who don't like to type 
 # too much:  ;-)
 c0 = +prevent-cookies
 c1 = -prevent-cookies
 #... etc.  Customize to your heart's content.
   

Some examples using our "shop" and "fragile" aliases from above. These would appear in the lower sections of an actions file as exceptions to the default actions (as defined in the upper section):

 # These sites are very complex and require
 # minimal interference.
 {fragile}
  .office.microsoft.com
  .windowsupdate.microsoft.com
  .nytimes.com

 # Shopping sites - but we still want to block ads.
 {shop}
  .quietpc.com
  .worldpay.com   # for quietpc.com
  .scan.co.uk

 # These shops require pop-ups also 
 {shop -kill-popups}
  .dabs.com
  .overclockers.co.uk
   

The "shop" and "fragile" aliases are often used for "problem" sites that require most actions to be disabled in order to function properly.

7.5. The Filter File

Any web page can be dynamically modified with the filter file. This modification can be removal, or re-writing, of any web page content, including tags and non-visible content. The default filter file is default.filter, located in the config directory.

This is potentially a very powerful feature, and requires knowledge of both "regular expression" and HTML in order create custom filters. But, there are a number of useful filters included with Privoxy for many common situations.

The included example file is divided into sections. Each section begins with the FILTER keyword, followed by the identifier for that section, e.g. "FILTER: webbugs". Each section performs a similar type of filtering, such as "html-annoyances".

This file uses regular expressions to alter or remove any string in the target page. The expressions can only operate on one line at a time. Some examples from the included default default.filter:

Stop web pages from displaying annoying messages in the status bar by deleting such references:

 FILTER: html-annoyances

 # New browser windows should be resizeable and have a location and status
 # bar. Make it so.
 #
 s/resizable="?(no|0)"?/resizable=1/ig s/noresize/yesresize/ig
 s/location="?(no|0)"?/location=1/ig s/status="?(no|0)"?/status=1/ig
 s/scrolling="?(no|0|Auto)"?/scrolling=1/ig
 s/menubar="?(no|0)"?/menubar=1/ig 

 # The <BLINK> tag was a crime!
 #
 s*<blink>|</blink>**ig

 # Is this evil? 
 #
 #s/framespacing="?(no|0)"?//ig
 #s/margin(height|width)=[0-9]*//gi
   

Just for kicks, replace any occurrence of "Microsoft" with "MicroSuck", and have a little fun with topical buzzwords:

 FILTER: fun

 s/microsoft(?!.com)/MicroSuck/ig

 # Buzzword Bingo:
 #
 s/industry-leading|cutting-edge|award-winning/<font color=red><b>BINGO!</b></font>/ig
   

Kill those pesky little web-bugs:

 # webbugs: Squish WebBugs (1x1 invisible GIFs used for user tracking)
 FILTER: webbugs

 s/<img\s+[^>]*?(width|height)\s*=\s*['"]?1\D[^>]*?(width|height)\s*=\s*['"]?1(\D[^>]*?)?>/<!-- Squished WebBug -->/sig
   

7.6. Templates

When Privoxy displays one of its internal pages, such as a 404 Not Found error page, it uses the appropriate template. On Linux, BSD, and Unix, these are located in /etc/privoxy/templates by default. These may be customized, if desired. cgi-style.css is used to control the HTML attributes (fonts, etc).

The default "Blocked" banner page with the bright red top banner, is called just "blocked". This may be customized or replaced with something else if desired.