[reblws]

The main difference between Chrome and Firefox extensions is that Chrome uses a callback-based API while Firefox's is based on promises. Other than that they're functionally the same aside from some differences in the manifest and the namespace (Chrome uses `chrome` while Firefox uses `browser`). I think Firefox has some backwards compatibility with the callback interface for easier porting but I haven't tried.

There's a nice polyfill by Mozilla so you can use their promise interface in Chrome but it was missing some important apis last I checked (sessions and optional permissions). https://github.com/mozilla/webextension-polyfill