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Firefox Release Notes

v.9.0, offered to release channel users on December 20th, 2011 Check out what’s new, the known issues and frequently asked questions about the latest released version of Firefox. As always, you’re encouraged to tell us what you think, or file a bug in Bugzilla.

What’s New in Firefox

The latest version of Firefox has the following changes:

Please see the complete list of changes in this version. Web and extension developers should also view the curated list of platform changes. You may also be interested in the list of changes in the previous version.

Note: Automatic updates for Mac OS X and Linux have been disabled while we investigate a possible issue affecting a small number of users. The issue is unlikely to impact new users.

External parties tracking Firefox release uptake should be aware that we manage and monitor the rate of automatic updates to ensure a smooth release. Users can always manually check for updates from the About Firefox window to see whether they are up to date.

Firefox Notes (First offered to release channel users on January 31, 2012)

Check out what’s new and known issues for this version of Firefox below. As always, you’re encouraged to tell us what you think, or file a bug in Bugzilla.

System Requirements

Before installing, make sure your computer meets the system requirements.


Mozilla provides Firefox for Windows, Linux, and Mac OS X in a variety of languages. You can get the latest released version of Firefox here or the latest development version of Firefox here.

For builds for other systems and languages not provided by Mozilla, see the Contributed Builds section at the end of this document.


Please note that installing a new version of Firefox will overwrite your existing installation of Firefox. You won’t lose any of your bookmarks or browsing history, but some of your extensions and other add-ons might not work until updates for them are made available.


You can remove Firefox with the Add/Remove Programs utility on Windows, by moving the Firefox application to the Trash on Mac OS X, or by deleting the containing folder on Linux.

By default, removing Firefox won’t remove your bookmarks, web browsing history, extensions or other add-ons. This data is stored in your profile folder, which can be found by going to the Help menu and selecting Troubleshooting Information.... The button next to the Profile Directory line in Application Basics will open your profile directory in your system's file explorer.

Please note that if you keep your profile, any version of Firefox that you install after removing Firefox will continue to use the bookmarks, web browsing history, add-ons, and other data from this profile folder.

Add-ons and Themes

You can get Add-ons and Themes by opening the Add-ons Manager, or by visiting the Add-ons Web site. Add-ons installed with previous versions of Firefox may not yet have been updated by their authors to work with this Firefox. If you wish to help test Add-ons, please install the Add-on Compatibility Reporter - your favorite Add-on author will appreciate it!

Known Issues

This list covers some of the known problems with Firefox which will be resolved in future versions:

All Systems
  • Some add-ons (particularly toolbars built with the FreeCause platform) may cause crashes on startup for some users. Please start Firefox in safe mode and disable any problematic toolbars (see bug 711794)
  • The Web Developer menu includes a new "Inspect" option. This is an early version of a developer tool that has already evolved substantially. If you're a web developer, we recommend you download Firefox Aurora and try out the improved version of this tool.
  • Users of the Twitter search plugin may see Twitter appear in the search provider list multiple times (see bug 690658)
  • Choosing the "Pop out" menu item while watching fullscreen YouTube videos may cause Firefox to hang (see bug 675645)
  • Roundcube, webmail software used by many hosting companies, incorrectly displays an ellipses in place of long email titles. The Roundcube team has been notified of the issue (see bug 680610)
  • Arabic text on does not display correctly. The BBC has been notified of the issue (see bug 674335)
  • Firefox will now display a corrupted content error when it detects certain types of misconfigured servers. This is not a Firefox issue, please contact the website owner (see bug 681140)
  • For some users, scrolling in the main GMail window will be slower than usual (see bug 579260)
  • If you try to start Firefox using a locked profile, it will crash (see bug 573369)
Microsoft Windows
  • Some users of Adobe Reader X have experienced instability when viewing PDF documents in the browser. Uninstalling and reinstalling Adobe Reader X has been determined to resolve the issue (see bug 640901)
  • Some ALPS touchpad drivers break scrolling in Firefox. A workaround has been identified (see bug 605357)
Mac OS X
  • For some users, the preference dialog is not shown and a rendering error (in the form of a white square) is shown instead. This is caused an add-on incorrectly setting Firefox preferences (see bug 641288)
  • Users running Mac OS X 10.7 may see a crash when the file chooser dialog is shown. Apple has been notified of the issue (see bug 670842)
  • Users running Mac OS X 10.7 are no longer able to use gestures to navigate. This is due to underlying operating system changes and is fixed by Mac OS X 10.7.2 (see bug 668953)
  • This version of Firefox will not work on Macintosh hardware with Power PC CPUs (see bug 587799)
Linux and Unix
  • The video control buttons may not work when viewing QuickTime videos with libtotem (see bug 625036)
  • Users compiling from source might need a newer gcc and libstdc++ as the build requirements have changed (see bug 578880)


  • Poorly designed or incompatible extensions can cause problems with your browser, including make it crash, slow down page display, etc. If you encounter strange problems relating to parts of the browser no longer working, the browser not starting, windows with strange or distorted appearance, degraded performance, etc, you may be suffering from Extension or Theme trouble. Restart the browser in Safe Mode. On Windows, start using the "Safe Mode" shortcut created in your Start menu or by running firefox.exe -safe-mode. On Linux, start with ./firefox -safe-mode and on Mac OS X, run:

    cd /Applications/
    ./firefox-bin -safe-mode

    When started in Safe Mode all extensions are disabled and the Default theme is used. Disable the Extension/Theme that is causing trouble and then start normally.
  • If you uninstall an extension that is installed with your user profile (i.e. you installed it from a Web page) and then wish to install it for all user profiles using the -install-global-extension command line flag, you must restart the browser once to cleanse the profile extensions datasource of traces of that extension before installing with the switch. If you do not do this you may end up with a jammed entry in the Extensions list and will be unable to install the extension globally.
  • If you encounter strange problems relating to bookmarks, downloads, window placement, toolbars, history, or other settings, it is recommended that you try creating a new profile and attempting to reproduce the problem before filing bugs. Create a new profile by running Firefox with the -P command line argument, choose the "Manage Profiles" button and then choose "Create Profile...". Migrate your settings files (Bookmarks, Saved Passwords, etc) over one by one, checking each time to see if the problems resurface. If you do find a particular profile data file is causing a problem, file a bug and attach the file.

Frequently Asked Questions

  1. What can I do to help?

    We need help from developers and the testing community to provide as much feedback as possible to make Firefox even better. Please tell us what you think or file a bug in Bugzilla.

  2. How can I preview future Firefox releases?

    You can preview the future of Firefox by joining our Aurora or Beta development channel.

  3. Where can I get extensions and themes (add-ons)?

    Extensions and Themes can be downloaded from Firefox Add-ons.

  4. Who makes Firefox?

    Lots of people. See Help->About Mozilla Firefox, and click the "global community" for a list of some of the people who have contributed to Firefox.

  5. Where’s the Firefox source code?

    A tarball of the Firefox source code is available for download. The latest development code can be obtained through Mercurial. Firefox-specific source is in mozilla-central's "browser", "toolkit", and "chrome" directories. Please follow the build instructions.

  6. Where is the mail client?

    Firefox works with whatever mail client is the default on your system. However, we recommend Mozilla Thunderbird, our next-generation email client and the perfect complement to Firefox.

Contributed Builds

Contributed builds are unofficial builds contributed by the Mozilla Community. They may be configured differently than the official Mozilla builds. They may also be optimized and/or tested for specific platforms. You can browse through the available contributed builds in the "contrib" directory on the FTP site.