Advanced notice: Browser extensions have been available in the market since 1997 and W3C has attempted for years to increase interoperability in this area. The mission of the Web Extensions Working Group is to specify the common core of cross-browser extension APIs.

The W3C Team is currently working on a charter for the Web Extensions Working Group. More information is available at:
https://lists.w3.org/Archives/Public/public-new-work/2025Aug/0001.html