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Firefox 3.6 Beta Release Notes

Beta revision 4: released November 26th, 2009 This is a beta version of the next feature release of the Firefox web browser, which will update itself during the beta period and eventually to the final release. The Mozilla community appreciates your feedback and assistance evaluating this preview of the next version of Firefox. You can help test Add-on compatibility by installing the Add-on Compatibility Reporter - your favorite Add-on author will appreciate it!

Please read below for more detailed information about what is new in this revision of the beta release.

About this release

Firefox 3.6 Beta (revision 4) is the latest development milestone of the next version of the Firefox web browser. As beta software, this release is considered to be stable and safe to use for daily web browsing, though the features and content may change before the final product release. At this time many Add-ons may not yet have been tested by their authors to ensure that they are compatible with this release. If you wish to help test Add-on compatibility, please install the Add-on Compatibility Reporter - your favorite Add-on author will appreciate it!

Check out what’s new, the known issues and frequently asked questions about the latest version of Firefox. Please tell us what you think, either by using this feedback form or by filing a bug in Bugzilla. We appreciate your input!

What’s New in Firefox 3.6 Beta (revision 4)

Firefox 3.6 Beta is built on Mozilla's Gecko 1.9.2 web rendering platform, which has been under development for several months and contains many improvements for web developers, Add-on developers and users. This version is also faster and more responsive than previous versions, and has been optimized to run on small device operating systems such as Windows CE and Maemo.

Developers can find out about all the changes and new features at the Mozilla Developer Center.

System Requirements

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


Mozilla provides Firefox 3.6 Beta for Windows, Linux, and Mac OS X in a variety of languages. You can get the latest version of the Firefox 3.6 Beta here. For builds for other systems and languages not provided by, see the Contributed Builds section at the end of this document.


Please note that installing Firefox 3.6 Beta will not 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 3.6 Beta 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.

Removing Firefox 3.6 Beta won’t remove your bookmarks, web browsing history, extensions or other add-ons. This data is stored in your profile folder, which is located in one of the following locations depending on your operating system:

Windows Vista Users\<UserName>\AppData\Roaming\Mozilla\Firefox
Windows 2000, XP, Server 2003 Documents and Settings\<UserName>\Application Data\Mozilla\Firefox
Mac OS X ~/Library/Application Support/Firefox
Linux and Unix systems ~/.mozilla/firefox

Any version of Firefox that you install after removing Firefox 3.6 (Beta) will continue to use the data from this profile folder.

Add-ons and Themes

Add-ons installed with previous versions of Firefox may not yet have been updated by their authors to work with Firefox 3.6 Beta. 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 3.6 Beta which will be resolved in future versions:

All Systems
  • The default position of tabs opened using the "Open in New Tab" control has changed to be to the immediate right of the current tab (see bug 465673)
  • The "Enable Java" checkbox has been removed from the Content panel of Options/Preferences. Instead, users can disable Java through the Add-ons Manager, available in the Tools menu (see bug 506985)
  • The "Properties" item in the context menu has been removed; for image properties, a new "Image Info" item will be added (see bug 513147)
  • If FIPS mode is enabled and certain files have been removed from the system, the browser may crash on startup (see bug 522041)
Mac OS X
  • Full screen video closes immediately (see bug 530654)


  • 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 Beta?

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

  4. Where’s the Firefox 3.6 Beta source code?

    A tarball of the Firefox 3.6 Beta (revision 3) 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 Beta 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.