įirefox was created in 2002 under the code name 'Phoenix' by the Mozilla community members who desired a standalone browser, rather than the Mozilla Application Suite bundle. An optimized version of Firefox is also available on the Amazon Fire TV, as one of the two main browsers available with Amazon's Silk Browser. However, the iOS version uses the WebKit layout engine instead of Gecko due to platform requirements, as with all other iOS web browsers.

Firefox is also available for Android and iOS. Its unofficial ports are available for various Unix and Unix-like operating systems, including FreeBSD, OpenBSD, NetBSD, illumos, and Solaris Unix. Firefox is available for Windows 7 and later versions, macOS, and Linux. In 2017, Firefox began incorporating new technology under the code name Quantum to promote parallelism and a more intuitive user interface.

Firefox uses the Gecko rendering engine to display web pages, which implements current and anticipated web standards. Mozilla Firefox or simply Firefox is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation.