This is taken directly from source with no modifications.
Firefox Focus for Android
Browse like no one’s watching. The new Firefox Focus automatically blocks a wide range of online trackers — from the moment you launch it to the second you leave it. Easily erase your history, passwords and cookies, so you won’t get followed by things like unwanted ads.
For more information please see the following links:
Updated as of: May 24th 2017
Gecko Debug version:
WebKit Debug version:
WebKit Beta version:
(NOTE: This may or may not work on your version of Android depending on what version of WebView you have enabled.)
Focus by Firefox, App for all devices (see above for details)
Source Code: https://github.com/mozilla-mobile/focus-android
Last Updated 2017-05-24