Today Mozilla released developer preview version of the new version of the mobile operating system Firefox OS 2.5. In addition to the several new features, a very important new feature is that now the owner of any Android device can test the Firefox OS.
To do this, simply install the APK-file without flashing or changing the operating system of your phone.
Firefox OS 2.5 is installed as a normal android application on your Android device.
The Firefox OS 2.5 adds support for extensions, like in the Firefox browser for personal computers, private browsing mode, and the ability to keep the site on the home screen.