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Google unveiled plans to upgrade the extension Manifest that Chromium-based browsers such as Google Chrome use to version 3 in early 2019. The initial draft was criticized heavily, especially for Google's plan to limit the webRequest API that content blockers and other extensions use. The new API, declarativeNetRequest, had filter limits and other restrictions that would mean the end for many ad blockers for Chrome.

Companies like Brave or Vivaldi voiced their concern over the proposed changes and let users know that they would do all that is in their power to retain support for Manifest V2 in their browsers.

Mozilla, maker of Firefox, revealed that it had no "immediate plans" not remove the blocking part of the webRequest API.

Google introduced Manifest V3 in Chrome 80 Canary in November 2019, and has now introduced the new manifest in Chrome 88 Beta.

Manifest V3 includes many useful additions and Google decided to focus on those improvements in the announcement. According to Google, Manifest V3 includes the following improvements over the previous version:

• Remotely hosted code is no longer supported. Google notes that remotely hosted code has been an attack vector that posed a "significant risk to user privacy and security".
  
• Performance is improved through the introduction of service workers (which replace background pages) and by moving to a "more declarative model for extension APIs".
  
• Privacy is improved by making more permissions optional and the ability to "withhold sensitive permissions at install time".
  

Google notes that it has received a lot of feedback when it published the first draft, and that it used the feedback to improve APIs, including the controversial declarativeNetRequest API. Company engineers added support for "multiple static rulesets, regular expressions within rules, declarative header modification, and more" to the API since then.

Google's Chrome Web Store will accept submissions of extensions that use Manifest V3 from January 2021 on when Chrome 88 hits the Stable channel. The company has not set a date yet for the removal of support for Manifest V2 extensions.

Andrey Meshkov, Co-founder and CTO of AdGuard, suggests that the maintainers of other Chromium-based browsers may be able to maintain support for Manifest V2 for "some time" but that it seems unlikely that support will be available indefinitely. Meshov believes that Mozilla will also replace Manifest V2 with V3 in the organization's Firefox web browser.

Now You: What will you do when Manifest V3 becomes the only Manifest supported by your browser?
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