Firefox Focus first launched on iOS, where Apple's WebKit is the only web engine permitted. Focus on Android followed a similar approach using Android's WebView so the Focus team could focus ;) on the app's user experience and privacy features instead of the web engine.

However, Focus (on Android) is now moving to "GeckoView", Firefox for Android's Gecko engine repackaged into a WebView-like component. GeckoView will be available for app developers (Mozilla or others) to build new browsers. Watch Mozilla's Hacks blog for news coming soon! :)

Here are instructions for test driving Focus+GeckoView now:

https://github.com/mozilla-mobile/focus-android/wiki/Release...