Firefox is already installed on Ubuntu as part of the normal installation. If you want to install a different (most commonly newer) version of Firefox on your Ubuntu system (or other GNU/Linux systems) that is also possible and is explained below.
Accessing it is easy. If you are using an installation of Ubuntu with no changes to the default Desktop, select Applications > Internet > Firefox Web Browser:
Firefox starts and a welcome window opens:
If you want to upgrade the version of Firefox included with Ubuntu to the latest version, such as a beta version or a new stable version, replacing your existing version, a detailed guide is available on the Ubuntu wiki at https://help.ubuntu.com/community/FirefoxNewVersion
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