Getting started with Adblock Plus

What is Adblock Plus? What can it do?

Adblock Plus is an extension for Firefox, Thunderbird, and several other applications with the primary goal of removing advertisements. For that, it will look at all requests made by web pages and block the request if the address the request should go to matches a filter in Adblock Plus. Out of the box, Adblock Plus comes without any filters whatsoever but will offer to add a filter subscription on first start — that is a list of filters maintained by other Adblock Plus users and will be updated automatically regularly. A filter subscription can be added later as well (see Choosing a filter subscription), but you can also create your own filters regardless of whether you use a filter subscription.

Blocking requests is limited to removing advertisements that are technically not part of the web page but downloaded separately. Because of that limitation, there is also an additional mechanism called “element hiding” which allows hiding parts of web pages based on some unique properties. The disadvantage here is that even hidden elements are still downloaded and require processing time in the browser. Also, creating element hiding rules is more complicated because you have to select the right set of properties — only the elements that need to be hidden should have those, not the required page content. Element Hiding Helper extension makes this task easier, yet creating good element hiding rules still requires much experimenting.

Installing Adblock Plus

Go to the Adblock Plus page on addons.mozilla.org and click the big green installation button. Confirm installation and restart the application when asked.

Alternatively, you can install from the installation page on this site. In addition to the usual multi-language build, this page also offers you the smaller Adblock Plus builds for one language only. However, you will need to allow installation from adblockplus.org.

Additional information:

First steps

Choosing a filter subscription

Adblock Plus “by itself” doesn’t do anything. It can see everything a web page attempts to load but it doesn’t know whether this attempt should be blocked. And that’s what you need filters for — filters will tell Adblock Plus what should be blocked. Usually, you won’t create filters yourself, instead you will add a filter subscription that is maintained by somebody else.

Subscriptions window in Adblock Plus

Which filter subscription should you choose? Adblock Plus offers you a few selected filter subscriptions on first start. The full list is much longer. However, you should not add all subscriptions you can get — each filter subscription contains filters that will in some cases block something that is not an advertisement, this is unavoidable. Usually, this will never be an issue for you, but you will be far more likely to hit this problem if you add too many filter subscriptions. As a rule of thumb, you should not use filter subscriptions with overlapping competencies. For example, using EasyList (targeted at English-language sites) with an EasyList supplement for your region (like Corset for Korean sites) is fine. However, Cédrics Liste (general filter list with focus on German sites) shouldn’t be used in combination with other filter subscriptions.

You can always change the filter subscriptions that you use by opening Adblock Plus preferences (press Ctrl+Shift+E). You can remove any filter subscriptions you have in that list, and you can add a new subscription by going to menu Filters / Add filter subscription. Once you are done with your changes click OK.

Disabling Adblock Plus on frequently used sites

Many web sites depend on advertising income, and if you visit a web site frequently you might want to allow their advertising — provided that this advertising isn’t too annoying. To do that, navigate to that site and click the arrow symbol next to the Adblock Plus icon in toolbar. From the menu you can choose “Disable on …” (you can undo that choice in the same way by unchecking this menu line).

Solving problems

What if Adblock Plus blocks too much?

It might happen that Adblock Plus prevents some site from functioning correctly. Usually, this is not a bug in Adblock Plus but a problem with the filters (or filter subscription) you are using, these filters tell Adblock Plus to block something that shouldn’t be blocked. You verify this by temporarily disabling Adblock Plus, if this “fixes” the problem you are dealing with a bad filter. You can investigate further by opening the list of blockable items on that site (press Ctrl+Shift+V). The items that have been blocked appear in red, and the filter that blocked it shows up in the “Filter” column. If there are multiple candidates, you should have a look at the “Type” column. If the site or a part of it is simply blank, you should be looking for a blocked frame. If the site displays as “text only” in default color and without background, you should be looking for a blocked stylesheet. Finally, if the site shows up correctly but “doesn’t work” (animation not running, nothing happens when buttons are clicked etc) then there is likely a script that shouldn’t be blocked.

Once you identified the problem, you can right-click the blocked item and choose “Disable filter …” from the context menu. If you guessed correctly the page will work again after your reload it. If not, you can right-click the same item again and choose “Re-enable filter …” from the context menu — try unblocking some other item. But even if everything works for you now, please notify the maintainer of the filter subscription that caused the issue (filter source will be shown in the tooltip for the blocked item). The contact information can usually be found on the list of filter subscriptions. In your message, please include the address of the page, a description of the problem (e.g. “warning message cannot be seen” or “when you click the red button nothing happens”) and ideally also the filter that caused the problem.

What if Adblock Plus doesn’t block an advertisement?

If you found an advertisement that Adblock Plus doesn’t block, please check first whether you are using the right filter subscription. For example, expecting a French filter subscription to block advertisements on a Bulgarian website is unrealistic — you should add a Bulgarian filter subscription for that job. If the filter subscription is right, then the subscription maintainer is probably simply unaware of the problem and you should tell him. The contact information can usually be found on the list of filter subscriptions. In your message, please include the address of the page and where you see an advertisement that should be blocked (it is not always obvious).

Of course, you can also block the advertisement yourself. The FAQ explain how this can be done for the easy cases and for the somewhat more complicated cases. Still, if you share with the filter subscription maintainer you will let other people benefit as well.

Uninstalling Adblock Plus

Adblock Plus is uninstalled like every other extension as well. Go to menu Tools / Add-ons, select Adblock Plus in the list and click the “Uninstall” button. MozillaZine Knowledge Base has more detailed instructions.

Note that Adblock Plus preferences are not removed when the extension is uninstalled. If you reinstall Adblock Plus later your configuration will be available again. If you want a clean start with Adblock Plus you should remove the directory “adblockplus” in your user profile (profile folder location for different applications and operating systems). Also, you should go to about:config and reset all preferences starting with “extensions.adblockplus” (to reset right-click a preference and choose Reset from the context menu).

Additional information:

Uninstalling in SeaMonkey