google-chrome-extension Tutorial => Porting to/from Firefox

Remarks

If you're using a Firefox version before 48, you'll also need an additional key in manifest.json called applications:

"applications": {
  "gecko": {
    "id": "[email protected]",
    "strict_min_version": "42.0",
    "strict_max_version": "50.*",
    "update_url": "https://example.com/updates.json"
  }
}

applications

Note:

Extension Signing:

With the release of Firefox 48, extension signing can no longer be disabled in the release and beta channel builds by using a preference. As outlined when extension signing was announced, we are publishing specialized builds that support this preference so developers can continue to test against the code that beta and release builds are generated from.

Status of WebExtensions:

WebExtensions are currently in an experimental alpha state. From Firefox 46, you can publish WebExtensions to Firefox users, just like any other add-on. We're aiming for a first stable release in Firefox 48.

UPD: Firefox 48 released 02.08.2016.

Links:

API support status - The list of APIs and their status.

Chrome incompatibilities

WebExtensions - JavaScript APIs, keys of manifest.json, tutorials, etc.