Changes

Unlike the web platform, we don't expect every browser to implement every aspect of WebExtensions in the same way. Hopefully there will be APIs that all browsers agree on, and they will work essentially the same way in all browsers. But there will also be APIs that are more browser-specific. For example, it's unlikely that Chrome will ever support a toolbar API, but Firefox probably will. Even even without perfect compatibility between browsers, a common API still has many advantages for extension developers. If developers stay within the common API, their extensions will automatically work across browsers. Even if developers choose to use browser-specific APIs, their extensions may be usable on other browsers through feature detection and fallbacks. For example, an extension using a toolbar API might be able to fall back to the browser action API on other browsers.