WebExtensions/Spec
Status: draft
Work on a cross-browser browser extension platform is currently taking place in the WebExtensions Community Group (WECG). This group was formally created in June, 2021 with the participation of Apple, Google, Microsoft and Mozilla.
The WECG is largely focused on facilitating communication amongst participating browser vendors and with the extension developer community. The editors draft of the WebExtensions specification is hosted on GitHub.
Previous specification work
Mozilla worked with Microsoft and Opera to implement browser extensions so that developers can write extensions that work across multiple browsers. A preliminary specification was created by the Browser Extension Community Group that matched Google Chrome's model so that WebExtensions will work on Chrome, Edge, Opera and Firefox.