Chrome Browser: What Google’s V3 Manifest Means for Ad Blockers

Already in 2018, Google presented version 3 of its “Manifesto”. Includes rules and interfaces that Chrome browser extensions must use. Shortly thereafter, ad blocker makers complained that the new specs restricted their options for filtering websites too much.

However, Google was not swayed by this, and the V3 Manifesto will be mandatory for all extensions distributed through the Chrome Store in January 2023. AdGuard has now released a beta version of its blocker that implements these specifications.

Fewer rule sets, fewer rules

The main innovation in Manifest V3 is the DeclarativeNetRequest API. Drastically limits the set of blocking rules. Only 50 rule sets are allowed per extension, of which a maximum of 10 can be active at the same time. Google also guarantees at least 30,000 unique rules per blocker.

However, the new manifest also sets a global maximum of 330,000 rules for all extensions. For comparison: a current AdGuard extension for Firefox on Mac already uses more than 220,000 filter rules by default.

Users also have to limit themselves, they can create a maximum of 5000 of their own rules. In total, the declarativeNetRequest API also accepts no more than 1,000 regular expressions.

The browser should crash

With the new API, extensions can no longer block or modify browser requests, only read them. They tell the browser how to handle requests. According to Google, this should prevent performance loss and protect user privacy.

The makers of AdGuard not only consider these limits to be too low. They criticize that Google’s V3 Manifesto introduces a new format for blocking rules that only the internal browser engine understands. This makes it difficult for ad blocker providers and third parties to create cross-browser lists. Therefore, the new blocker includes a library that rewrites the previously used text form rules into the JSON files expected by Chrome.

Two years ago, Microsoft implemented the innovations of Manifest V3 in its Chrome-based Edge browser. Like Google, it highlighted the expected gains in performance and privacy.

You can find more information about workarounds on Adguards Blocker in the V3 Manifest on the company blog. You can find more information about the declarativeNetRequest API in the Google Developer Blog.

(psst)