5. 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.

5.1. Controlling Privoxy with Your Web Browser

Privoxy can be reached by the special URL http://p.p/ (or alternately http://config.privoxy.org/), which is an internal page. You will see the following section:


Please choose from the following options:

    * Show information about the current configuration
    * Show the source code version numbers
    * Show the client's request headers.
    * Show which actions apply to a URL and why
    * Toggle Privoxy on or off
    * Edit the actions list

 

This should be self-explanatory. Note the last item is an editor for the "actions list", which is where much of 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. Privoxy will automatically detect any changes to these files.

"Toggle Privoxy On or Off" is handy for sites that might have problems with your current actions and filters, or just to test if a site misbehaves, whether it is Privoxy causing the problem or not. Privoxy continues to run as a proxy in this case, but all filtering is disabled.

5.2. 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 possibly aggressive by some standards. For the time being, there are only three default configuration files (this may change in time):

default.action and default.filter can use Perl style regular expressions for maximum flexibility. All files use the "#" character to denote a comment. Such lines are not processed by Privoxy. After making any changes, there is no need to restart Privoxy in order for the changes to take effect. Privoxy should detect such changes automatically.

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.

5.3. 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:

  blockfile blocklist.ini
   

Indicates that the blockfile is named "blocklist.ini". (A default installation does not use this.)

A "#" indicates a comment. Any part of a line following a "#" is ignored, except if the "#" is preceded by a "\".

Thus, by placing a "#" at the start of an existing configuration line, you can make it a comment and it will be treated as if it weren't there. This is called "commenting out" an option and can be useful to turn off features: If you comment out the "logfile" line, Privoxy will not log to a file at all. Watch for the "default:" section in each explanation to see what happens if the option is left unset (or commented out).

Long lines can be continued on the next line by using a "\" as the very last character.

There are various aspects of Privoxy behavior that can be tuned.

5.3.1. Defining Other Configuration Files

Privoxy can use a number of other files to tell it what ads to block, what cookies to accept, and perform other functions. This section of the configuration file tells Privoxy where to find all those other files.

On Windows and AmigaOS, Privoxy looks for these files in the same directory as the executable. On Unix and OS/2, Privoxy looks for these files in the current working directory. In either case, an absolute path name can be used to avoid problems.

When development goes modular and multi-user, the blocker, filter, and per-user config will be stored in subdirectories of "confdir". For now, only confdir/templates is used for storing HTML templates for CGI results.

The location of the configuration files:

  confdir /etc/privoxy       # No trailing /, please.
   

The directory where all logging (i.e. logfile and jarfile) takes place. No trailing "/", please:

  logdir /var/log/privoxy
   

Note that all file specifications below are relative to the above two directories!

The "default.action" file contains patterns to specify the actions to apply to requests for each site. Default: Cookies to and from all destinations are kept only during the current browser session (i.e. they are not saved to disk). Pop-ups are disabled for all sites. All sites are filtered through selected sections of "default.filter". No sites are blocked. Privoxy displays a checkboard type pattern for filtered ads and other images. The syntax of this file is explained in detail below. Other "actions" files are included, and you are free to use any of them. They have varying degrees of aggressiveness.

  actionsfile default.action
   

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. Default: whatever the developers are playing with :-/

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.

  filterfile default.filter
   

The logfile is where all logging and error messages are written. 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 Redhat, 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.

Default: Log to the a file named logfile. Comment out to disable logging.

  logfile logfile
   

The "jarfile" defines where Privoxy stores the cookies it intercepts. Note that if you use a "jarfile", it may grow quite large. Default: Don't store intercepted cookies.

  #jarfile jarfile
   

If you specify a "trustfile", Privoxy will only allow access to sites that are named in the trustfile. You can also mark sites as trusted referrers, 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". This is a very restrictive feature that typical users most probably want to leave disabled. Default: Disabled, don't use the trust mechanism.

  #trustfile trust
   

If you use the trust mechanism, it is a good idea to write up some on-line documentation about your blocking policy and to specify the URL(s) here. They will appear on the page that your users receive when they try to access untrusted content. Use multiple times for multiple URLs. Default: Don't display links on the "untrusted" info page.

  trust-info-url http://www.example.com/why_we_block.html
  trust-info-url http://www.example.com/what_we_allow.html
   

5.3.2. Other Configuration Options

This part of the configuration file contains options that control how Privoxy operates.

"Admin-address" should be set to the email address of the proxy administrator. It is used in many of the proxy-generated pages. Default: fill@me.in.please.

  #admin-address fill@me.in.please
   

"Proxy-info-url" can be set to a URL that contains more info about this Privoxy installation, it's configuration and policies. It is used in many of the proxy-generated pages and its use is highly recommended in multi-user installations, since your users will want to know why certain content is blocked or modified. Default: Don't show a link to on-line documentation.

  proxy-info-url http://www.example.com/proxy.html
   

"Listen-address" specifies the address and port where Privoxy will listen for connections from your Web browser. The default is to listen on the localhost port 8118, and this is suitable for most users. (In your web browser, under proxy configuration, list the proxy server as "localhost" and the port as "8118").

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. The syntax is "listen-address [<ip-address>]:<port>". 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 "aclfile" above), or a firewall.

For 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
   

If you want it to listen on all addresses (including the outside connection):

  listen-address :8118
   

If you do this, consider using ACLs (see "aclfile" above). Note: you will need to point your browser(s) to the address and port that you have configured here. Default: localhost:8118 (127.0.0.1:8118).

The debug option sets the level of debugging information to log in the logfile (and to the console in the Windows version). A debug level of 1 is informative because it will show you each request as it happens. Higher levels of debug are probably only of interest to developers.

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

It is highly recommended that you enable ERROR reporting (debug 8192), at least until v3.0 is released.

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, do not enable anything else.

Multiple "debug" directives, are OK - they're logical-OR'd together.

  debug 15 # same as setting the first 4 listed above
   

Default:

  debug 1 # URLs
  debug 4096 # Info
  debug 8192 # Errors - *we highly recommended enabling this*
   

Privoxy normally uses "multi-threading", a software technique that permits it to handle many different requests simultaneously. In some cases you may wish to disable this -- particularly if you're trying to debug a problem. The "single-threaded" option forces Privoxy to handle requests sequentially. Default: Multi-threaded mode.

  #single-threaded
   

"toggle" allows you to temporarily disable all Privoxy's filtering. Just set "toggle 0".

The Windows version of Privoxy puts an icon in the system tray, which also allows you to change this option. If you right-click on that icon (or select the "Options" menu), one choice is "Enable". Clicking on enable toggles Privoxy on and off. This is useful if you want to temporarily disable Privoxy, e.g., to access a site that requires cookies which you would otherwise have blocked. This can also be toggled via a web browser at the Privoxy internal address of http://p.p on any platform.

"toggle 1" means Privoxy runs normally, "toggle 0" means that Privoxy becomes a non-anonymizing non-blocking proxy. Default: 1 (on).

  toggle 1
   

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.

The buffer-limit option lets you set the maximum size in Kbytes that each buffer may use. When the documents buffer exceeds this size, it is flushed to the client unfiltered and no further attempt to filter the rest of it is made. Remember that there may multiple threads running, which might require increasing the "buffer-limit" Kbytes each, unless you have enabled "single-threaded" above.

  buffer-limit 4069
   

To enable the web-based default.action file editor set enable-edit-actions to 1, or 0 to disable. Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect. This internal page can be reached at http://p.p.

Security note: If this is enabled, anyone who can use the proxy can edit the actions file, and their changes will affect all users. For shared proxies, you probably want to disable this. Default: enabled.

  enable-edit-actions 1
   

Allow Privoxy to be toggled on and off remotely, using your web browser. Set "enable-remote-toggle"to 1 to enable, and 0 to disable. Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect.

Security note: If this is enabled, anyone who can use the proxy can toggle it on or off (see http://p.p), and their changes will affect all users. For shared proxies, you probably want to disable this. Default: enabled.

  enable-remote-toggle 1
   

5.3.3. Access Control List (ACL)

Access controls are included at the request of some ISPs and systems administrators, and are not usually needed by individual users. Please note 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.

If no access settings are specified, the proxy talks to anyone that connects. If any access settings file are specified, then the proxy talks only to IP addresses permitted somewhere in this file and not denied later in this file.

Summary -- if using an ACL:

Client must have permission to receive service.

LAST match in ACL wins.

Default behavior is to deny service.

The syntax for an entry in the Access Control List is:

  ACTION    SRC_ADDR[/SRC_MASKLEN]    [ DST_ADDR[/DST_MASKLEN] ]
   

Where the individual fields are:

 ACTION      = "permit-access" or "deny-access"

 SRC_ADDR    = client hostname or dotted IP address
 SRC_MASKLEN = number of bits in the subnet mask for the source

 DST_ADDR    = server or forwarder hostname or dotted IP address
 DST_MASKLEN = number of bits in the subnet mask for the target
   

The field separator (FS) is whitespace (space or tab).

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

Here are a few examples to show how the ACL features work:

"localhost" is OK -- no DST_ADDR implies that ALL destination addresses are OK:

  permit-access localhost
   

A silly example to illustrate permitting any host on the class-C subnet with Privoxy to go anywhere:

  permit-access www.privoxy.com/24
   

Except deny one particular IP address from using it at all:

  deny-access ident.privoxy.com
   

You can also specify an explicit network address and subnet mask. Explicit addresses do not have to be resolved to be used.

  permit-access 207.153.200.0/24
   

A subnet mask of 0 matches anything, so the next line permits everyone.

  permit-access 0.0.0.0/0
   

Note, you cannot say:

  permit-access .org
   

to allow all *.org domains. Every IP address listed must resolve fully.

An ISP may want to provide a Privoxy that is accessible by "the world" and yet restrict use of some of their private content to hosts on its internal network (i.e. its own subscribers). Say, for instance the ISP owns the Class-B IP address block 123.124.0.0 (a 16 bit netmask). This is how they could do it:

 permit-access 0.0.0.0/0 0.0.0.0/0   # other clients can go anywhere 
                                       # with the following exceptions:
 
 deny-access   0.0.0.0/0   123.124.0.0/16 # block all external requests for
                                          # sites on the ISP's network

 permit 0.0.0.0/0 www.my_isp.com        # except for the ISP's main 
                                          # web site

 permit 123.124.0.0/16 0.0.0.0/0          # the ISP's clients can go 
                                          # anywhere
   

Note that if some hostnames are listed with multiple IP addresses, the primary value returned by DNS (via gethostbyname()) is used. Default: Anyone can access the proxy.

5.3.4. Forwarding

This feature allows chaining of HTTP requests via multiple proxies. It can be used to better protect privacy and confidentiality when accessing specific domains by routing requests to those domains to a special purpose filtering proxy such as lpwa.com. Or to use a caching proxy to speed up browsing.

It can also be used in an environment with multiple networks to route requests via multiple gateways allowing transparent access to multiple networks without having to modify browser configurations.

Also specified here are SOCKS proxies. Privoxy SOCKS 4 and SOCKS 4A. The difference is that SOCKS 4A will resolve the target hostname using DNS on the SOCKS server, not our local DNS client.

The syntax of each line is:

 forward target_domain[:port] http_proxy_host[:port]
 forward-socks4 target_domain[:port] socks_proxy_host[:port] http_proxy_host[:port]
 forward-socks4a target_domain[:port] socks_proxy_host[:port] http_proxy_host[:port]
   

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

Lines are checked in sequence, and the last match wins.

There is an implicit line equivalent to the following, which specifies that anything not finding a match on the list is to go out without forwarding or gateway protocol, like so:

  forward .* . # implicit
   

In the following common configuration, everything goes to Lucent's LPWA, except SSL on port 443 (which it doesn't handle):

 forward .* lpwa.com:8000
 forward :443 .
   

Some users have reported difficulties related to LPWA's use of "." as the last element of the domain, and have said that this can be fixed with this:

  forward lpwa. lpwa.com:8000
   

(NOTE: the syntax for specifying target_domain has changed since the previous paragraph was written -- it will not work now. More information is welcome.)

In this fictitious example, everything goes via an ISP's caching proxy, except requests to that ISP:

 forward .* caching.myisp.net:8000
 forward myisp.net .
   

For the @home network, we're told the forwarding configuration is this:

  forward .* proxy:8080
   

Also, we're told they insist on getting cookies and JavaScript, so you should allow cookies from home.com. We consider JavaScript a potential security risk. Java need not be enabled.

In this example direct connections are made to all "internal" domains, but everything else goes through Lucent's LPWA by way of the company's SOCKS gateway to the Internet.

 forward-socks4 .* lpwa.com:8000 firewall.my_company.com:1080
 forward my_company.com .
   

This is how you could set up a site that always uses SOCKS but no forwarders:

  forward-socks4a .* . firewall.my_company.com:1080
   

An advanced example for network administrators:

If you have links to multiple ISPs that provide various special content to their subscribers, you can configure forwarding to pass requests to the specific host that's connected to that ISP so that everybody can see all of the content on all of the ISPs.

This is a bit tricky, but here's an example:

host-a has a PPP connection to isp-a.com. And host-b has a PPP connection to isp-b.com. host-a can run a Privoxy proxy with forwarding like this:

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

host-b can run a Privoxy proxy with forwarding like this:

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

Now, anyone on the Internet (including users on host-a and host-b) can set their browser's proxy to either host-a or host-b and be able to browse the content on isp-a or isp-b.

Here's another practical example, for University of Kent at Canterbury students with a network connection in their room, who need to use the University's Squid web cache.

 forward *. ssbcache.ukc.ac.uk:3128  # Use the proxy, except for:
 forward .ukc.ac.uk .  # Anything on the same domain as us
 forward * .  # Host with no domain specified
 forward 129.12.*.* .  # A dotted IP on our /16 network.
 forward 127.*.*.* .  # Loopback address
 forward localhost.localdomain .  # Loopback address
 forward www.ukc.mirror.ac.uk .  # Specific host
   

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

Your squid configuration could then look like this (assuming that the IP address of the box is 192.168.0.1 ):

  # Define Privoxy as parent cache 
  
  cache_peer 192.168.0.1 parent 8118 0 no-query

  # don't listen to the whole world
  http_port 192.168.0.1:3128

  # define the local lan
  acl mylocallan src 192.168.0.1-192.168.0.5/255.255.255.255

  # grant access for http to local lan
  http_access allow mylocallan
  
  # Define ACL for protocol FTP 
  acl FTP proto FTP 

  # Do not forward ACL FTP to privoxy
  always_direct allow FTP 

  # Do not forward ACL CONNECT (https) to privoxy
  always_direct allow CONNECT 

  # Forward the rest to privoxy
  never_direct allow all 
   

5.3.5. 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
   

5.4. The Actions File

The "default.action" file (formerly actionsfile or ijb.action) is used to define what actions Privoxy takes, and thus determines how ad images, cookies and various other aspects of HTTP content and transactions are handled. These can be accepted or rejected for all sites, or just those sites you choose. See below for a complete list of actions.

Anything you want can blocked, including ads, banners, or just some obnoxious URL that you would rather not see. Cookies can be accepted or rejected, or accepted only during the current browser session (i.e. not written to disk). Changes to default.action should be immediately visible to Privoxy without the need to restart.

Note that some sites may misbehave, or possibly not work at all with some actions. This may require some tinkering with the rules to get the most mileage of Privoxy's features, and still be able to see and enjoy just what you want to. There is no general rule of thumb on these things. There just are too many variables, and sites are always changing.

The easiest way to edit the "actions" file is with a browser by loading http://p.p/, and then select "Edit Actions List". A text editor can also be used.

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. You can trace this process by visiting http://p.p/show-url-info.

There are four types of lines in this file: comments (begin with a "#" character), actions, aliases and patterns, all of which are explained below, as well as the configuration file syntax that Privoxy understands.

5.4.1. URL Domain and Path Syntax

Generally, a pattern has the form <domain>/<path>, where both the <domain> and <path> part are optional. If you only specify a domain part, the "/" can be left out:

www.example.com - is a domain only pattern and will match any request to "www.example.com".

www.example.com/ - means exactly the same.

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. So would match any page named "index.html" on any site.

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

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 or sub-domain that ENDS in ".example.com".

www. - matches any domain that STARTS with "www".

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. And you can define character classes in square brackets and they 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.com - matches "www1.example.com", "www4.example.com", "wwwd.example.com", "wwwz.example.com", etc., but not "wwww.example.com".

If Privoxy was compiled with "pcre" support (the default), Perl compatible regular expressions can be used. These are more flexible and powerful than other types of "regular expressions". See the pcre/docs/ directory or "man perlre" (also available on http://www.perldoc.com/perl5.6/pod/perlre.html) for details. A brief discussion of regular expressions is in the Appendix. For instance:

/.*/advert[0-9]+\.jpe?g - would match a URL from any domain, with any path that includes "advert" followed immediately by one or more digits, then a "." and ending in either "jpeg" or "jpg". So we match "example.com/ads/advert2.jpg", and "www.example.com/ads/banners/advert39.jpeg", but not "www.example.com/ads/banners/advert39.gif" (no gifs in the example pattern).

Please 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.

5.4.2. Actions

Actions are enabled if preceded with a "+", and disabled if preceded with a "-". Actions are invoked by enclosing the action name in curly braces (e.g. {+some_action}), followed by a list of URLs to which the action applies. There are three classes of actions:

  • Boolean (e.g. "+/-block"):

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

  • parameterized (e.g. "+/-hide-user-agent"):

      {+name{param}}  # enable action and set parameter to "param"
      {-name}         # disable action
         

  • Multi-value (e.g. "{+/-add-header{Name: value}}", "{+/-wafer{name=value}}"):

      {+name{param}}   # enable action and add parameter "param"
      {-name{param}}   # remove the parameter "param"
      {-name}          # disable this action totally
         

If nothing is specified in this 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 default.action file 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.

The list of valid Privoxy "actions" are:

  • Add the specified HTTP header, which is not checked for validity. You may specify this many times to specify many different headers:

      +add-header{Name: value}
         

  • Block this URL totally. In a default installation, a "blocked" URL will result in bright red banner that says "BLOCKED", with a reason why it is being blocked, and an option to see it anyway. The page displayed for this is the "blocked" template file.

      +block
         

  • 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).

      +deanimate-gifs{last}
      +deanimate-gifs{first}
         

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

      +downgrade
         

  • 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.

    The "+fast-redirects" option enables interception of these types of requests by Privoxy, who will cut off all but the last valid URL in the request and send a local redirect back to your browser without contacting the intermediate site(s).

      +fast-redirects
         

  • Apply the filters in the section_header section of the default.filter file to the site(s). default.filter sections are grouped according to like functionality. Filters can be used to re-write any of the raw page content. This is a potentially a very powerful feature!

     +filter{section_header}
         

    Filter sections that are pre-defined in the supplied default.filter include:

    html-annoyances: Get rid of particularly annoying HTML abuse.

    js-annoyances: Get rid of particularly annoying JavaScript abuse

    no-poups: Kill all popups in JS and HTML

    frameset-borders: Give frames a border

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

    no-refresh: Automatic refresh sucks on auto-dialup lines

    fun: Text replacements for subversive browsing fun!

    nimda: Remove (virus) Nimda code.

    banners-by-size: Kill banners by size

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

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

      +hide-forwarded
         

  • If the browser sends a "From:" header containing your e-mail address, this either completely removes the header ("block"), or changes it to the specified e-mail address.

      +hide-from{block}
      +hide-from{spam@sittingduck.xqq}
         

  • Don't send the "Referer:" (sic) header to the web site. You can block it, forge a URL to the same server as the request (which is preferred because some sites will not send images otherwise) or set it to a constant, user defined string of your choice.

      +hide-referer{block}
      +hide-referer{forge}
      +hide-referer{http://nowhere.com}
         

  • Alternative spelling of "+hide-referer". It has the 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 "referer".)

      +hide-referrer{...}
         

  • Change the "User-Agent:" header so web servers can't tell your browser type. Warning! This breaks many web sites. Specify the user-agent value you want. Example, pretend to be using Netscape on Linux:

      +hide-user-agent{Mozilla (X11; I; Linux 2.0.32 i586)}
         

  • Treat this URL as an image. This only matters if it's also "+block"ed, in which case a "blocked" image can be sent rather than a HTML page. See "+image-blocker{}" below for the control over what is actually sent. If you want invisible ads, they should be defined as images and blocked. And also, "image-blocker" should be set to "blank". 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, cannot be treated as an image. Forcing an "image" in this situation just will not work.

      +image
         

  • Decides what to do with URLs that end up tagged with "{+block +image}", e.g an advertizement. There are five options. "-image-blocker" will send a HTML "blocked" page, usually resulting in a "broken image" icon. "+image-blocker{blank}" will send a 1x1 transparent GIF image. And finally, "+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. "+image-blocker{pattern}" will send a checkboard type pattern

      +image-blocker{blank}
      +image-blocker{pattern}
      +image-blocker{http://p.p/send-banner}
         

  • By default (i.e. in the absence of a "+limit-connect" action), Privoxy will only allow CONNECT requests to port 443, which is the standard port for https as a precaution.

    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):

      +limit-connect{443} # This is the default and need no 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.
         

  • "+no-compression" prevents the website from compressing the data. Some websites do this, which can be a problem for Privoxy, since "+filter", "+no-popup" and "+gif-deanimate" will not work on compressed data. This will slow down connections to those websites, though. Default is "no-compression" is turned on.

      +nocompression
         

  • If the website sets cookies, "no-cookies-keep" 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. Default: on.

      +no-cookies-keep
         

  • Prevent the website from reading cookies:

      +no-cookies-read
         

  • Prevent the website from setting cookies:

      +no-cookies-set
         

  • Filter the website through a built-in filter to disable those obnoxious JavaScript pop-up windows via window.open(), etc. The two alternative spellings are equivalent.

      +no-popup
      +no-popups
         

  • This action only applies if you are using a jarfile for saving cookies. It sends a cookie to every site stating that you do not accept any copyright on cookies sent to you, and asking them not to track you. Of course, this is a (relatively) unique header they could use to track you.

      +vanilla-wafer
         

  • This allows you to add an arbitrary cookie. It can be specified multiple times in order to add as many cookies as you like.

      +wafer{name=value}
         

The meaning of any of the above is reversed by preceding the action with a "-", in place of the "+".

Some examples:

Turn off cookies by default, then allow a few through for specified sites:

 # Turn off all persistent cookies
 { +no-cookies-read }
 { +no-cookies-set }
 # Allow cookies for this browser session ONLY
 { +no-cookies-keep }

 # Exceptions to the above, sites that benefit from persistent cookies
 { -no-cookies-read }
 { -no-cookies-set }
 { -no-cookies-keep }
 .javasoft.com
 .sun.com
 .yahoo.com
 .msdn.microsoft.com
 .redhat.com

 # Alternative way of saying the same thing
 {-no-cookies-set -no-cookies-read -no-cookies-keep}
 .sourceforge.net
 .sf.net
   

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

 # Turn them off!
 {+fast-redirects}
 
 # 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 refilterfile, and make one exception for sourceforge:

 # Run everything through the filter file, using only the
 # specified sections:
 +filter{html-annoyances} +filter{js-annoyances} +filter{no-popups}\
 +filter{webbugs} +filter{nimda} +filter{banners-by-size}
              
 # Then disable filtering of code from sourceforge!
 {-filter}
 .cvs.sourceforge.net
   

Now some URLs that we want "blocked" (normally generates the "blocked" banner). Many of these use regular expressions that will expand to match multiple URLs:

  # Blocklist:
  {+block}
  /.*/(.*[-_.])?ads?[0-9]?(/|[-_.].*|\.(gif|jpe?g))
  /.*/(.*[-_.])?count(er)?(\.cgi|\.dll|\.exe|[?/])
  /.*/(ng)?adclient\.cgi
  /.*/(plain|live|rotate)[-_.]?ads?/
  /.*/(sponsor)s?[0-9]?/
  /.*/_?(plain|live)?ads?(-banners)?/
  /.*/abanners/
  /.*/ad(sdna_image|gifs?)/
  /.*/ad(server|stream|juggler)\.(cgi|pl|dll|exe)
  /.*/adbanners/
  /.*/adserver
  /.*/adstream\.cgi
  /.*/adv((er)?ts?|ertis(ing|ements?))?/
  /.*/banner_?ads/
  /.*/banners?/
  /.*/banners?\.cgi/
  /.*/cgi-bin/centralad/getimage
  /.*/images/addver\.gif
  /.*/images/marketing/.*\.(gif|jpe?g)
  /.*/popupads/
  /.*/siteads/
  /.*/sponsor.*\.gif
  /.*/sponsors?[0-9]?/
  /.*/advert[0-9]+\.jpg
  /Media/Images/Adds/
  /ad_images/
  /adimages/
  /.*/ads/
  /bannerfarm/
  /grafikk/annonse/
  /graphics/defaultAd/
  /image\.ng/AdType
  /image\.ng/transactionID
  /images/.*/.*_anim\.gif # alvin brattli
  /ip_img/.*\.(gif|jpe?g)
  /rotateads/
  /rotations/ 
  /worldnet/ad\.cgi
  /cgi-bin/nph-adclick.exe/
  /.*/Image/BannerAdvertising/
  /.*/ad-bin/
  /.*/adlib/server\.cgi
  /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 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.

5.4.3. 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 anything else in the default.actionfile! And there can only be one set of "aliases" defined.

Now let's define a few aliases:

 # Useful custom aliases we can use later. These must come first!
 {{alias}}
 +no-cookies = +no-cookies-set +no-cookies-read
 -no-cookies = -no-cookies-set -no-cookies-read
 fragile     = -block -no-cookies -filter -fast-redirects -hide-referer -no-popups
 shop        = -no-cookies -filter -fast-redirects
 +imageblock = +block +image

 #For people who don't like to type too much:  ;-)
 c0 = +no-cookies
 c1 = -no-cookies
 c2 = -no-cookies-set +no-cookies-read
 c3 = +no-cookies-set -no-cookies-read
 #... etc.  Customize to your heart's content.
   

Some examples using our "shop" and "fragile" aliases from above:

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

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

 # These shops require pop-ups
 {shop -no-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.

5.5. 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
   

5.6. 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.

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.