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Firefox 3.6 Release Notes

v.3.6.22, released September 6th, 2011
Check out what’s new, the known issues and frequently asked questions about the 3.6 version of Firefox. As always, you’re encouraged to tell us what you think, either using this feedback form or by filing a bug in Bugzilla.

We strongly recommend that all Firefox 3.6 users upgrade to the very latest version available.

What’s New in Firefox 3.6.22

Firefox 3.6.22 fixes the following issues found in previous versions of Firefox 3.6:

You may also be interested in the Firefox 3.6.21 release notes for a list of changes in the previous version.

System Requirements

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


Mozilla provides Firefox 3.6 for Windows, Linux, and Mac OS X in a variety of languages. You can get the latest version of Firefox 3.6 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 Firefox 3.6 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 reinstall an older version later if you wish to downgrade.


You can remove Firefox 3.6 through the Control Panel in the Start Menu on Windows, by removing the Firefox application on OS X, or by removing the firefox folder on Linux.

By default, removing Firefox 3.6 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 3.6 will continue to use the bookmarks, web browsing history, add-ons, and other data from this profile folder.

Extensions and Themes

Extensions installed under Firefox 3.5 may be incompatible and/or require updates to work with Firefox 3.6. Please report any issues to the maintainer of the extension. When you install Firefox 3.6 all of your Extensions and Themes will be disabled until Firefox 3.6 determines that either a) they are compatible with the Firefox 3.5 release or b) there are newer versions available that are compatible.

Known Issues

This list covers some of the known problems with Firefox 3.6, which will be resolved in future releases:

All Systems
  • If FIPS mode is enabled and certain files have been removed from the system, the browser may crash on startup (see bug 522041)
Microsoft Windows
  • Content over certain Flash videos may not disappear when the video plays (see bug 571313)
  • Older Flash videos on may fail to play. CNet has been notified of the issue (see bug 569104)
  • Some slower machines may see degraded mouse responsiveness when viewing certain Flash videos (see bug 561818)
Linux and Unix
  • Firefox may have difficulty playing system sounds in some distributions of Linux (see bug 536996)
  • Zooming out on some sites may result in grey or black lines appearing (see bug 468496)


  • 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 read these notes and the bug filing instructions before reporting any bugs to Bugzilla. You can also give us your feedback through this feedback form.

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

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

  3. Who makes Firefox 3.6?

    Lots of people. See Help->About Mozilla Firefox, Credits for a list of some of the people who have contributed to Firefox 3.6.

  4. Where’s the Firefox 3.6 source code?

    A tarball of the Firefox 3.6 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.

  5. Where is the mail client?

    Firefox 3.6 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

These are unofficial builds and 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 on the FTP site.