Chrome’s “Manifest V3” plan to limit ad-blocking extensions is delayed

For several years now, Google has wanted to kill Chrome’s current extension system in favor of a more limited one, creating more restrictions on filtering extensions that block ads and/or work to preserve the user’s privacy. The new extension system, called “Manifest V3” technically hit the stable channel in January 2021, but Chrome still supports the older, more powerful system, Manifest V2. The first steps toward winding down Manifest V2 were supposed to start January 2023, but as 9to5Google first spotted, Google now says it delayed the mandatory switch to Manifest V3 and won’t even have a new timeline for a V2 shutdown ready until March.

The old timeline started in January 2023, when beta versions of Chrome would start running “experiments” that disable Manifest V2. This would move to the stable version in June, with the Chrome Web Store banning Manifest V2 extensions in January 2024. The new timeline is that there is no timeline, and every step is now listed as “postponed” or “under review.”

In a post about the delay, Chrome Extensions Developer Advocate Simeon Vincent says, “We’ve heard your feedback on common challenges posed by the migration, specifically the service worker’s inability to use DOM capabilities and the current hard limit on extension service worker lifetimes. We’re mitigating the former with the Offscreen Documents API (added in Chrome 109) and are actively pursuing a solution to the latter.” After adding that every step of the timeline is on hold, Vincent said, “Expect to hear more about the updated phase-out plan and schedule by March of 2023.”

Google’s statement only addresses the second controversial change to Manifest V3: turning off an extension’s ability to launch a hidden background page due to background processing. Google wants all background processing to happen in service workers, but that’s a complicated environment compared to normal web development and comes with many more limitations. Google’s delay is only about trying to fix some of these background limitations.

The new Manifest V3 timeline, which only says that everything is delayed.
Enlarge / The new Manifest V3 timeline, which only says that everything is delayed.

Google

Google’s post does not mention filtering add-ons, so it does not sound like the world’s biggest ad company is having a change of heart about ad blockers. The big problem for those extensions is killing the “WebRequest API,” which allows ad blockers and other filtering tools to modify Chrome’s network requests on the fly. Usually, this is used to create huge lists of websites (ad servers) the extensions want to block access to. Google has sort of thrown these extensions a bone by creating a new API that allows for a limited list of URL blocking, but this is only a static list of 30,000 URLs, while a typical uBlock Origin install comes with 300,000 dynamic filtering rules. Some ad blockers will try and play within these rules with the Manifest V3 version, but Google’s going to erode their effectiveness and doesn’t want to implement any of the common-sense solutions that would allow them to keep functioning at the current level.

“Deceitful and threatening”

Google started this mess in 2018 with a blog post outlining a plan for “Trustworthy Chrome Extensions, by default.” As part of the Manifest V3 rollout, Google’s official story is that it wanted to cut down on “overly-broad access” given to extensions and that a more limited extension platform would “enable more performant” extensions. The fun side effect of all that is more limited ad blocking, which would conveniently help Google’s bottom line. The old timeline would have finally implemented the full Manifest V3 transition six years after this initial blog post, but now it sounds like it will take even longer.

The Electronic Frontier Foundation is not buying Google’s sales pitch and called Manifest V3 “deceitful and threatening” around a year ago. The EFF said Manifest V3 “will restrict the capabilities of web extensions—especially those that are designed to monitor, modify, and compute alongside the conversation your browser has with the websites you visit.” The privacy group said it’s “doubtful Mv3 will do much for security” too, since it only limits filtering website content, not collecting it, so malicious extensions could still vacuum all your data. The EFF also says performance isn’t a valid excuse either, citing a study showing that ad downloading and rendering degrades browser performance. If Google’s worried about security, it could police the extension store better.

The Chrome team seems committed to a heel turn lately. The group also refused to block tracking cookies until it can first build a tracking and advertising system into Chrome (this has also been repeatedly delayed). If people get tired of Chrome’s user-hostile changes that prop up Google’s business model, there are alternatives. Some Chromium-based forks like Brave and Vivaldi have pledged to keep Manifest V2 running when Google turns it off. Of course, there’s also always Firefox, which says it will transition to Manifest V3 along with Google but will re-add the WebRequest API that filtering add-ons rely on.

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