Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. Firefox uses the Gecko layout engine to render web pages, which implements current and anticipated web standards. In 2017, Firefox began incorporating new technology under the code name Quantum to promote parallelism and a more intuitive user interface. Firefox is officially available for Windows 7 or newer, macOS, and Linux. Its unofficial ports are available for various Unix and Unix-like operating systems including FreeBSD, OpenBSD, NetBSD, illumos, and Solaris Unix. Firefox is also available for Android and iOS; however, the iOS version uses the WebKit layout engine instead of Gecko due to platform limitations, as with all other iOS web browsers. 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.
Firefox was created in 2002 under the codename "Phoenix" by the Mozilla community members who desired a standalone browser, rather than the Mozilla Application Suite bundle. During its beta phase, Firefox proved to be popular with its testers and was praised for its speed, security, and add-ons compared to Microsoft's then-dominant Internet Explorer 6. Firefox was released on November 9, 2004, and challenged Internet Explorer's dominance with 60 million downloads within nine months. Firefox is the spiritual successor of Netscape Navigator, as the Mozilla community was created by Netscape in 1998 before their acquisition by AOL.
Firefox usage grew to a peak of 32.21% at the end of 2009, with version 3.5 overtaking Internet Explorer 7, although not all versions of Internet Explorer as a whole. Usage then declined in competition with Google Chrome. As of July 2020, Firefox has 8.48% usage share as a "desktop" browser according to StatCounter, but 7.58% according to NetMarketShare, making it the third-most popular browser after Google Chrome with 69% and Safari with 8.74%; usage share across all platforms is lower and is third-most popular overall at 4.25% according to StatCounter, and 3.55% according to NetMarketShare. According to Mozilla, in December 2014, there were half a billion Firefox users around the world. Although virtually all countries have Google Chrome as their mainly used web browser, Firefox still has over 50% desktop usage in Cuba and Eritrea, over 40% usage in Armenia, and over 20% usage in Germany, Austria, Poland, Luxembourg, Iran, Myanmar, East Timor, Burkina Faso, Madagascar, Cameroon, Ethiopia, Mali, Togo and Uganda.