Google Chrome will be shutting down its older, more capable extension system, Manifest V2, in favor of exclusively using the more limited Manifest V3. The deeply controversial Manifest V3 system was announced in 2019, and the full switch has been delayed a million times, but now Google says it's really going to make the transition: As previously announced, the phase-out of older Chrome extensions is starting next week.
Google Chrome has been working toward a plan for a new, more limited extension system for a while now. Google says it created "Manifest V3" extensions with the goal of "improving the security, privacy, performance, and trustworthiness of the extension ecosystem."
Other groups don't agree with Google's description, like the Electronic Frontier Foundation (EFF), which called Manifest V3 "deceitful and threatening" back when it was first announced in 2019, saying the new system "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." It has a whole article out detailing how Manifest V3 won't help security.
Comments from the Firefox team have also cast doubt on Google's justification for Manifest V3. In a talk about the implications of Manifest V3, Philipp Kewisch, Firefox's Add-ons operations manager, said, "for malicious add-ons, we feel for Firefox it has been on a manageable level, and since the add-ons are mostly interested in grabbing data, they can still do that with the current web request API [in Manifest V3]." Firefox plans to support Manifest V3 because Chrome is the world's most popular browser, and it wants extensions to be cross-browser compatible, but it has no plans to turn off support for Manifest V2.