GNUzilla and IceCat

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 nonfree software as plug-ins and addons. Also their trademark license imposes requirements for the distribution of modified versions that make it inconvenient to exercise freedom 3.

Privacy protection features

  • LibreJS: GNU LibreJS aims to address the JavaScript problem described in Richard Stallman's article The JavaScript Trap.
  • JShelter: Mitigates potential threats from JavaScript, including fingerprinting, tracking, and data collection. Slightly modifies the results of API calls, differently on different domains, so that the cross-site fingerprint is not stable. Applies security counter-measures that are likely not to break web pages. Allows fine-grained control over the restrictions and counter-measures applied to each domain.
  • Fingerprinting countermeasures: Fingerprinting is a series of techniques allowing to uniquely identify a browser based on specific characterisics of that particular instance (like what fonts are available in that machine). Unlike cookies, the user cannot opt-out of being tracked this way; so the browser has to avoid giving away these kinds of hints.


The IceCat project does not currently distribute binaries, but the GNU Guix package manager can be used to install IceCat on GNU/Linux systems based on 64-bit AMD/Intel processors.

Guix can also be used to build IceCat source tarballs that are suitable for building IceCat natively for other operating systems.

If you don't use Guix and would like to use IceCat, you could consider maintaining an IceCat package for your distribution. On any POSIX system, IceCat source tarballs can be generated from the corresponding Firefox ESR sources using the scripts available in the Git repository of GNUzilla.

Free add-ons and plugins

GNUzilla runs its own plugin finder service at

Online help and documentation

Community driven manuals are available at LibrePlanet.

IRC channel

Some of the GNUzilla and GNU IceCat maintainers and users hang out in the #icecat channel on the Libera.Chat IRC network. You are welcome to join the channel using your IRC client to chat and/or ask questions about GNUzilla and IceCat. Please note that depending on people's availability, it is possible that your question may not be answered immediately. As such, please wait patiently (and keep your IRC client connected to the network and present in the channel!) until someone sees and replies.

If you try without success, please try emailing one of GNUzilla's mailing lists, listed below.

Mailing lists

The GNUzilla project uses a number of mailing lists, as follows:

To subscribe to the mailing lists, you may either use the mailman web interface (click on each list name and follow the instructions), or send an empty email with a Subject: header line of just “subscribe” to, replacing listname with any of the list names above (e.g. help-gnuzilla).

Found a bug? Have a suggestion? Please report it to the bug-gnuzilla list, trying to specify all the information that could be involved: platform, program version (the command icecat --version will report this), and build tools version if building from source code. Please report both the observed and the expected behaviors.

Getting involved

Development of IceCat, and GNU in general, is a volunteer effort, and you can contribute. For information, please read How to help GNU. If you'd like to get involved, please join our mailing lists and say hi!

The GNUzilla project is currently maintained by Ruben Rodriguez, Amin Bandali, and Mark H. Weaver. Please use the mailing lists for contact.

Origin of the name

The name “IceCat” was coined to show our relationship to the Mozilla Firefox browser. Ice isn't Fire and a Cat isn't a Fox, so it is clearly a different package (we don't want Mozilla blamed for our mistakes, nor cause confusion with their trademarks), but is equally clearly intimately related (of course nearly all of the work comes from the Mozilla foundation effort, so we want to give credit).

The gNewSense BurningDog browser and the Debian IceWeasel browser are similarly derived from Firefox, also with the intent of being free software. Technically, however, these projects are maintained entirely independently of IceCat. (Previously, this GNU browser project was also named IceWeasel, but that proved confusing.)

About GNU and the GNU Philosophy

The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software—free as in freedom, not price. Its principal sponsor is the Free Software Foundation.

The free software philosophy is the root and motivation of the guidelines and goals of the whole free software movement, a worldwide community.

Please join us!