Mozilla has revealed how it plans to adopt manifest V3 in Firefox The company said that Firefox browser will fully adopt the next iteration of the network expansion platform by the end of 2022. Before that, it will launch a new developer preview plan to collect feedback from web developers.
What is manifest V3
Manifest V3 is the latest set of changes in the network expansion platform to make the expansion more secure, faster and privacy friendly. It was first announced by Google in 2019. One of the most controversial changes in manifest V3 is to cancel the web request API and use the new declarative net request API instead. The developer community has widely criticized this change because it deprives extensions of many useful functions and makes them less effective. Google Chrome has stopped accepting new extensions based on manifest V2, and the existing manifest V2 extensions will stop working after January 2023.
Mozilla wants to implement it in different ways
Mozilla said it was aware of some controversial changes proposed in manifest V3 and its weakening effect on advertising interceptors and other extensions. To this end, Mozilla said that it will adopt a different approach from Google browser when implementing manifest v3. Mozilla believes that the new declarative web request API is not a perfect substitute for webrequest API, which limits the scope of advertising blockers and privacy extensions. Therefore, Firefox will retain support for "block webrequest" in manifest V3 and also support declarativenetrequest.
"Mozilla will maintain support for blocking webrequest in MV3. To maximize compatibility with other browsers, we will also ship support for declarativenetrequest. We will continue to work with content blockers and other major consumers of the API to identify appropriate current and future alternatives," wrote rob Wu, Mozilla's senior software engineer.
Mozilla also doesn't like the background service used by chrome because it doesn't support many use cases and requires developers to rewrite a large part of the extension code. Mozilla proposed event pages last year to solve these shortcomings, and said that this proposal was welcomed by the community. Next, it was fully supported in the implementation of Firefox's manifest v3. Mozilla said that for compatibility reasons, it will also support service workers because Mozilla recognizes that they are an event driven environment with a defined lifetime, are already part of the network platform and have good cross browser support.
"In Firefox, we have decided to support event pages in MV3, and our developer preview will not include service workers (we are continuing to support these service workers for future versions). This will help developers more easily migrate existing persistent background pages to support MV3, while retaining access to all DOM related functions in MV2."