Mozilla is developing a variant of Firefox for the Windows 8 Modern UI. As of this writing, it comes with the Firefox Nightly for Windows build, and is activated when you set it as the default browser for your Windows 8 system. So far, Metro Firefox is a very basic browser with a minimal feature set. It sports a mobile-centric UI, which is essentially identical to that of the Android version of Firefox. Its present incarnation doesn’t offer a browsing experience that is faster, or otherwise better than Internet Explorer 10. But Firefox is, for now, the only alternative web browser designed to adhere to the Modern UI guidelines.