4.1. Quickstart to Ad Blocking
Ad blocking is but one of Privoxy's + array of features. Many of these features are for the technically minded advanced + user. But, ad and banner blocking is surely common ground for everybody.
+ This section will provide a quick summary of ad blocking so + you can get up to speed quickly without having to read the more extensive + information provided below, though this is highly recommeneded.
First a bit of a warning ... blocking ads is much like blocking SPAM: the + more aggressive you are about it, the more likely you are to block + things that were not intended. So there is a trade off here. If you want + extreme ad free browsing, be prepared to deal with more + "problem" sites, and to spend more time adjusting the + configuration to solve these unintended consequences. In short, there is + not an easy way to eliminate all ads. Either take + the easy way and settle for most ads blocked with the + default configuration, or jump in and tweak it for your personal surfing + habits and preferences.
Secondly, a brief explanation of Privoxy's + "actions". "Actions" in this context, are + the directives we use to tell Privoxy to perform + some task relating to HTTP transactions (i.e. web browsing). We tell + Privoxy to take some "action". Each + action has a unique name and function. While there are many potential + actions in Privoxy's + arsenal, only a few are used for ad blocking. Actions, and action + configuration files, are explained in depth below.
Actions are specified in Privoxy's configuration, + followed by one or more URLs to which the action should apply. URLs + can actually be URL type patterns that use + wildcards so they can apply potentially to a range of similar URLs. The + actions, together with the URL patterns are called a section.
When you connect to a website, the full URL will either match one or more + of the sections as defined in Privoxy's configuration, + or not. If so, then Privoxy will perform the + respective actions. If not, then nothing special happens. Futhermore, web + pages may contain embedded, secondary URLs that your web browser will + use to load additional components of the page, as it parses the + original page's HTML content. An ad image for instance, is just a URL + embedded in the page somewhere. The image itself may be on the same server, + or a server somewhere else on the Internet. Complex web pages will have many + such embedded URLs.
The actions we need to know about for ad blocking are: block, handle-as-image, and + set-image-blocker:
block - this action stops + any contact between your browser and any URL patterns that match this + action's configuration. It can be used for blocking ads, but also anything + that is determined to be unwanted. By itself, it simply stops any + communication with the remote server and sends Privoxy's + own built-in BLOCKED page instead to let you now what has happened. +
handle-as-image - + tells Privoxy to treat this URL as an image. + Privoxy's default configuration already does this + for all common image types (e.g. GIF), but there are many situations where this + is not as easy to determine. So we'll force it in these cases. This is particularly + important for ad blocking, since only if we know that it's an image, we can replace + it by an image instead of the BLOCKED page, which would only result in a + "broken image" icon. There are some limitations to this though. For + instance, you can't just brute-force an image substituion for an entire HTML page + in most situations. +
set-image-blocker - tells + Privoxy what to display in place of an ad image that + has hit a block rule. For this to come into play, the URL must match a + block action somewhere in the + configuration, and, it must also match an + handle-as-image action. +
The configuration options on what to display instead of the ad are: +
pattern - a checkboard pattern, so that an ad + replacement is obvious. This is the default. + blank - A very small empty GIF image is displayed. + This is the so-called "invisible" configuration option. + http://<URL> - A redirect to any image anywhere + of the user's choosing (advanced usage). +
The quickest way to adjust any of these settings is with your browser through + the special Privoxy editor at http://config.privoxy.org/show-status + (shortcut: http://p.p/show-status). This + is an internal page, and does not require Internet access. Select the + appropriate "actions" file, and click + "Edit". It is best to put personal or + local preferences in user.action to further tweak your new browsing - experience. +> since this is not + meant to be overwritten during upgrades, and will over-ride the settings in + other files. Here you can insert new "actions", and URLs for ad + blocking or other purposes, and make other adjustments to the configuration. + Privoxy will detect these changes automatically.
A quick and simple step by step example:
Right click on the ad image to be blocked, then select + "Copy Link Location" from the + pop-up menu. +
Set your browser to + http://config.privoxy.org/show-status +
Find user.action in the top section, and click + on "Edit": +
+You should have a section with only + block listed under + "Actions:". + If not, click a "Insert new section below" + button, and in the new section that just appeared, click the + Edit button right under the word "Actions:". + This will bring up a list of all actions. Find + block near the top, and click + in the "Enabled" column, then "Submit" + just below the list. +
Now, in the block actions section, + click the "Add" button, and paste the URL the + browser got from "Copy Link Location". + Remove the http:// at the beginning of the URL. Then, click + "Submit" (or + "OK" if in a pop-up window). +
Now go back to the original page, and press SHIFT-Reload + (or flush all browser caches). The image should be gone now.
This is a very crude and simple example. There might be good reasons to use a + wildcard pattern match to include potentially similar images from the same + site. For a more extensive explanation of "patterns", and + the entire actions concept, see the Actions + section.
For advanced users who want to hand edit their config files, you might want + to now go to the Actions Files Tutorial. + The ideas explained thererin also apply to the web-based editor.