Starting in June 2023 and Chrome 115, Google “may run experiments to turn off support for Manifest V2 extensions in all channels, including stable channel.” Also starting in June, the Chrome Web Store will stop accepting Manifest V2 extensions, and they’ll be hidden from view. In January 2024, Manifest V2 extensions will be removed from the store entirely.
Google says Manifest V3 is “one of the most significant shifts in the extensions platform since it launched a decade ago.” The company claims that the more limited platform is meant to bring “enhancements in security, privacy, and performance.” Privacy groups like the Electronic Frontier Foundation (EFF) dispute this description and say that if Google really cared about the security of the extension store, it could just police the store more actively using actual humans instead of limiting the capabilities of all extensions.
The big killer for ad block extensions comes from changes to the way network request modifications work. Google says that “rather than intercepting a request and modifying it procedurally, the extension asks Chrome to evaluate and modify requests on its behalf.” Chrome’s built-in solution forces ad blockers and privacy extensions to use the primitive solution of a raw list of blocked URLs rather than the dynamic filtering rules implemented by something like uBlock Origin. That list of URLs is limited to 30,000 entries, whereas a normal ad block extension can come with upward of 300,000 rules.