GNU IceCat, formerly known as GNU IceWeasel,is a free software rebranding of the Mozilla Firefox web browser distributed by the GNU Project. It is compatible with both the GNU/Linux and OS X (10.4 and 10.5) operating systems.
The GNU Project keeps IceCat in synchronization with upstream development of Firefox while removing all trademarked artwork. It also maintains a large list of free software plugins. In addition, it features a few security features not found in the mainline Firefox browser.