Changes

The Chrome extension API was designed to work well with process separation and we are certainly taking inspiration from it and copying functionality where it makes sense. However, there will be differences, and the goal of WebExtensions is not to copy Chrome or allow Chrome extensions to run unmodified in Firefox, but to simplify cross-browser development by providing commonly-supported methods and interfaces. We won't implement all of Chrome's APIs. And , and Chrome is unlikely to implement some of the APIs we add. Imagine the APIs as a [https://en.wikipedia.org/wiki/Venn_diagram Venn diagram]. In the middle are cross-browser APIs for content scripts, tabs, and windows. In the Firefox side are APIs for toolbars and sidebarsand other UI elements. On the Chrome side are APIs for Google's cloud services.

Unlike the web platform, we don't expect every browser to implement every aspect of WebExtensions in the same way. But , 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 should work with minimal (or no!) modifications across browsers. Even if developers choose to use browser-specific APIs, their extensions may be usable on other browsers through feature detection and fallbacks, or through using browser-specific APIs that provide similar functionality. For As an example, an extension using a toolbar API might be able to fall back to the a browser action API on other browsers.