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Firefox 3.6 Release Candidate Release Notes

Candidate 1: released January 8th, 2009 This is a release candidate of the next feature release of the Firefox web browser, which may update itself periodically and will eventually be identical 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 release candidate.

About this release

Firefox 3.6 Release Candidate 1 is the latest development milestone of the next version of the Firefox web browser. As a release candidate, this is considered to be stable and safe to use for daily web browsing, and represents the features and content that will be in the final product release. At this time most Add-ons have been tested by their authors to ensure that they are compatible with this release. If you experience problems with 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 need your input!

What’s New in Firefox 3.6 Release Candidate 1

Firefox 3.6 Release Candidate 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 Release Candidate for Windows, Linux, and Mac OS X in a variety of languages. You can get the latest version of the Firefox 3.6 Release Candidate 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 Release Candidate 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 Release Candidate 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 Release Candidate 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 (Release Candidate) 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 Release Candidate. 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 Release Candidate which will be resolved in future releases:

All Systems
  • JavaScript tracing is not enabled for Web Workers, resulting in slower than usual JavaScript execution time (see bug 538440)
  • If FIPS mode is enabled and certain files have been removed from the system, the browser may crash on startup (see bug 522041)
  • If you have the "reading pane" option set in Hotmail, the scroll arrows will not work properly (see bug 511075)
Mac OS X
  • On some versions of OSX, Firefox will not be able to open local files from the Finder if they have spaces in the filename (see bug 530064)
Linux and Unix
  • Firefox may have difficulty playing system sounds in some distributions of Linux (see bug 536996)


  • 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 Release Candidate?

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

  4. Where’s the Firefox 3.6 Release Candidate source code?

    A tarball of the Firefox 3.6 Release Candidate 1 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 Release Candidate 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.