icecat man page

IceCat — GNU version of Firefox browser


icecat [ options ... ] [URL]


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:

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.) 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.

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.)

Extensions included to this version of IceCat:

- LibreJS
 GNU LibreJS aims to address the JavaScript problem described in Richard
 Stallman's article The JavaScript Trap.

- SpyBlock
 Blocks privacy trackers while in normal browsing mode, and all third party
 requests when in private browsing mode. Based on Adblock Plus.

- AboutIceCat
 Adds a custom "about:icecat" homepage with links to information about the
 free software and privacy features in IceCat, and check-boxes to enable
 and disable the ones more prone to break websites.

- HTML5-video-everywhere
 Uses the native video player to play embedded videos from different sources

- 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 that kind of hints.

`icecat' generates a man page out of `--help' and `--version' output.

where options include:

X11 options


X display to use


Make X calls synchronous

--g-fatal-warnings Make all warnings fatal

IceCat options

-h or --help

Print this message.

-v or --version

Print IceCat version.

-P <profile>

Start with <profile>.

--profile <path>

Start with profile at <path>.


Start with migration wizard.


Start with ProfileManager.


Do not accept or send remote commands; implies --new-instance.


Open new instance, not a new window in running instance.

--UILocale <locale> Start with <locale> resources as UI Locale.


Disables extensions and themes for this session.


Open the Browser Console.


Open the Browser Toolbox.


Open DevTools on initial load.

--start-debugger-server [port|path] Start the debugger server on a TCP port or Unix domain socket path.

Defaults to TCP port 6000.


Open a browser window.

--new-window <url> Open <url> in a new window.

--new-tab <url>

Open <url> in a new tab.

--private-window <url> Open <url> in a new private window.


Open Preferences dialog.

--search <term>

Search <term> with your default search engine.

--recording <file> Record drawing for a given URL.

--recording-output <file> Specify destination file for a drawing recording.

--setDefaultBrowser Set this app as the default browser.

Gnuzilla IceCat 52.8.0


/usr/bin/icecat - icecat executable

/usr/lib(64)/icecat-52.8.0/icecat-bin - icecat executable


To report a bug, please mail to




For a full list of the people who are credited with making a contribution to Mozilla, see .

See Also


May 2018 IceCat 52.8.0 User Commands