Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. A Net Applications survey put Firefox at 25% of the recorded usage share of web browsers as of November 2009, making it the second most popular browser in terms of current use worldwide after Microsoft's Internet Explorer, and the most used browser independent of any one operating system.
To display web pages, Firefox uses the Gecko layout engine, which implements most current web standards in addition to several features which are intended to anticipate likely additions to the standards.
Latest Firefox features include tabbed browsing, spell checking, incremental find, live bookmarking, a download manager, private browsing, location-aware browsing (aka "geolocation") based exclusively on a Google service and an integrated search system that uses Google by default in most localizations. Functions can be added through add-ons, created by third-party developers, of which there is a wide selection, a feature that has attracted many of Firefox's users.
Firefox runs on various versions of Microsoft Windows, Mac OS X, Linux, and many other Unix-like operating systems. Its current stable release is version 3.5.6, released on December 15, 2009. Firefox's source code is free software, released under a tri-license GNU GPL/GNU LGPL/MPL.