AdGuard launches Manifest V3 compatible ad-blocker for Chrome

AdGuard, the company best known for its content blocking solution, launched what it calls the "world's first ad blocker built on Manifest V3".

Chrome and Chromium-based browser users who have not followed the news regarding the future of extensions in the browsers, may need a quick explanation to better understand what is going to happen in the coming months and years.

Google announced plans to release a new Manifest for extensions in 2018. Manifest V3 defines what extensions can and can't do in the Chrome web browser, and any other browser that implements it. Extension developers, privacy advocates and users criticized Manifest V3 shortly thereafter. The developer of uBlock Origin, who maintains one of the most respected content blockers, said that the release of Manifest V3 could mean the end uBlock Origin for Chrome.

Some browser makers, including Mozilla, maker of Firefox, stated openly that they would not implement the limiting changes of Manifest V3. Google made some concessions, but went ahead with the launching of Manifest V3 in the company's Chrome web browser.

Starting in January 2023, extension developers may no longer publish new Manifest V2 extensions or update existing ones. From June 2023 onward, Manifest V2 extensions won't run in Chrome anymore.

In other words: extension developers need to update their extensions to be compatible with the new Manifest V3 or end development for Chrome. Some Chromium-based browsers may modify the default behavior to support Manifest V2 extensions, but most won't, probably.

AdGuard MV3 Browser extension

AdGuard published a new browser extension for Chrome and other Chromium-based browsers that is based on Manifest V3. Users of AdGuard do not need the extension, as the main solution runs system-wide.

Work on the extension started in mid-2021. The developers note that the new APIs of Manifest V3 caused a lot of headache during development. While they managed to produce a working content blocker based on Manifest V3, they concede that it has certain limitations that Manifest V2 content blockers did not have.

One of the main issues of Manifest V3 is that it imposes a fixed limit of 330,000 rules for all extensions installed in Chrome. Any one extension has guaranteed access to 30,000 rules. The number may sound like much, but when you realize that modern content blockers rely on tens of thousands of even hundred thousands of rules, the limitation becomes apparent right away.

Take uBlock Origin as an example. The default configuration of uBlock Origin uses 80435 network filters and 45243 cosmetic filters; that is already more than four times the minimum guaranteed rules limit. Users may add their own custom rules to many content blockers or subscribe to more rules listings. It is easy to reach the 330,000 rules limit with just one extension.

Now imagine that other extensions are installed that rely on rules. These compete with each other then when it comes to the limits.

Dynamic rules have an even stricter limit of 5000, which includes a limit of 1000 regular expression rules. When the limit is exceeded, only the first 5000 rules will be applied by the content blocker, while all other rules have no effect.

AdGuard MV3 Browser takes that into account. The developers have added warnings to the extension that inform users when the rules limitation is forcing the extension to reduce the number of rules that it supports. In fact, the developers note that even the basic filter lists, which is the primary list of AdGuard, may be disabled in the worst case, as it has more than 30,000 rules. For users, it can mean that the installed content blocker does nothing at all.

Closing Words

AdGuard's new browser extension for Chrome demonstrates that content blockers are possible under Manifest V3. Compared to Manifest V2 content blockers, Manifest V3 extensions can be less powerful due to the artificial rules limits of Manifest V3. Especially the competing part is troublesome, as extensions may stop working if rules limits are reached.

Most Chrome users may want to switch to another browser when Manifest V3 becomes the standard to get a reliable protection and not a chaotic one.

Now You: are you affected by Manifest V3?

AdGuard launches Manifest V3 compatible ad-blocker for Chrome