They're using the WebExtension model of isolated extensions with permissions. They're not going to limit themselves to any competitor's API, they'll build a su

They're using the WebExtension model of isolated extensions with permissions. They're not going to limit themselves to any competitor's API, they'll build a superset by consulting with the developers of popular extensions. Tab Mix Plus being the 15th most popular extension, it's pretty certain they'll be consulted on the new APIs. Quoting from the announcement: > A major challenge we face is that many Firefox add-ons cannot possibly be built using either WebExtensions or the SDK as they currently exist. Over the coming year, we will seek feedback from the development community, and will continue to develop and extend the WebExtension API to support as much of the functionality needed by the most popular Firefox extensions as possible.