GNUzilla is the GNU version of the Mozilla suite, and GNU IceCat is
the GNU version of the Firefox browser. Its main advantage is an
ethical one: it is entirely free software. While the Firefox source
code from the Mozilla project is free software, they distribute and
recommend non-free software as plug-ins and addons.

In addition, GNU IceCat includes some privacy protection features,
included in a separate addon:

1. Some sites refer to zero-size images on other hosts to keep track
   of cookies. When IceCat detects this mechanism it blocks cookies
   from the site hosting the zero-length image file. (It is possible
   to re-enable such a site by removing it from the blocked hosts
   list.)

2. Other sites rewrite the host name in links redirecting the user to
   another site, mainly to "spy" on clicks. When this behavior is
   detected, IceCat shows a message alerting the user.