Firefox is a free and open source web browser produced by Mozilla. It has a GPL and is designed to work on many platforms. Firefox supports third party pluggins, and has a large support community.
Firefox runs on various operating systems including Microsoft Windows, Linux, Mac OS X, and unofficially, FreeBSD as well as several other platforms.
To display web pages, Firefox uses the Gecko layout engine, which implements most current web standards in addition to several features that are intended to anticipate likely additions to the standards.