It was clear even when it was first announced in a paper in 2018 that Google's Manifest V3, a new extension API for Chrome, would present a big problem for developers of extensions designed to block ads, but also trackers and certain types of malware – and for users who want improved privacy and control over their browsing experience.
Manifest V3 was first incorporated into Chrome 88 and released in January 2021. Since early 2022, new extensions using Manifest V2 are no longer accepted in the Chrome Web Store, and the last part of the phasing out of this API, which will break all extensions based on it, is expected to take place by January 2023.
Some developers of this privacy-friendly type of software have given up on Chrome and are recommending alternative browsers, while others, like AdGuard, have decided to try to find a way to “live” with Google's new, restrictive-by-design script-limiting rules.
Google, on the other hand, sells these new features as improvements of both privacy and security. Since Google also offers its own ad-blocker (“limiter”), critics add anti-competitive motivations behind the possible reasons to get rid of V2 and make life difficult for developers of blocking extensions.
On the technical side, what V3 does is change webREquest (used to access data on the internet) in such a way that it prevents extensions from modifying data before a browser user sees it – negating the purpose of blocking ads (and other unwanted elements).
AdGuard is reported to be the first developer to come up with a V3-compatible ad-blocker, currently in the experimental stage. The bad news is that the “compatibility” here seems to be a workaround that, by AdGuard's own admission, weakens the effectiveness of the extension.
But that seems to be the trade-off between having any independent-of-Google ad-blocker on Chrome, and having none.
For one thing, the V3-compliant version has no choice but to limit filtering rules and dynamic, user-set rules to 30,000 and 5,000, respectively.
Rules can no longer be loaded to the filtering engine from AdGuard's server, causing delays, and filtering logs are no longer available to users.
“Although the experimental extension is not as effective as its predecessor, most users won't feel the difference,” claims AdGuard.