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Firefox Release Notes

Release Notes tell you what’s new in Firefox. As always, we welcome your feedback. You can also file a bug in Bugzilla or see the system requirements of this release.

49.0 Firefox Release

September 20, 2016

Version 49.0, first offered to Release channel users on September 20, 2016

We'd also like to extend a special thank you to all of the new Mozillians who contributed to this release of Firefox!


  • Updated Firefox Login Manager to allow HTTPS pages to use saved HTTP logins. It’s one more way Firefox is supporting Let’s Encrypt and helping users transition to a more secure web.

  • Added features to Reader Mode that make it easier on the eyes and the ears

    • Controls that allow users to adjust the width and line spacing of
    • Narrate, which reads the content of a page out loud
  • Improved video performance for users on systems that support SSSE3 without hardware acceleration

  • Added context menu controls to HTML5 audio and video that let users loops files or play files at 1.25x speed

  • Enhancements for Mac users

    • Improved performance on OS X systems without hardware acceleration
    • Improved appearance of anti-aliased OS X fonts
  • Improvements in about:memory reports for tracking font memory usage

  • Improve performance on Windows systems without hardware acceleration

  • Support of Widevine CDM through the EME API under GNU/Linux


  • Fixed an issue that prevented users from updating Firefox for Mac unless they originally installed Firefox. Now, those users as well as any user with administrative credentials can update Firefox.

  • Various security fixes


  • Ended Firefox for Mac support for OS X 10.6, 10.7, and 10.8.

  • Ended Firefox for Windows support for SSE processors

  • Removed Firefox Hello

  • Re-enabled the default for Graphite2 font shaping

  • UPDATE: 2016-10-17. Asynchronous rendering of the Flash plugins is now enabled by default. This should improve performance and reduce crashes for sites that use the Flash plugin.

  • UPDATE: 2016-10-17. Default preference layers.allow-d3d9-fallback set to false, to fix graphics glitches for some users.

  • Default search engine changed to Yahoo for Chinese (Traditional) locale.



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