
GNU IceCat is the GNU version of the Firefox browser. It aim to be based on the the current official release of Firefox Extended Support Release (ESR) with removal of trademarked artwork and proprietary components. Important differences between Mozilla's Firefox and GNU IceCat is that IceCat has a focus on freedom and privacy.
However, IceCat is not a straight fork of Firefox ESR; instead, it is a parallel effort that works closely with and re-bases in synchronization on the latest Firefox ESR as the upstream supplier, with patches merged upstream whenever possible; although it should be noted that additional security updates are customized to IceCat occasionally.