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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.

47.0 Firefox Release

June 7, 2016

Version 47.0, first offered to Release channel users on June 7, 2016

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


  • Support for Google’s Widevine CDM on Windows and Mac OS X so streaming services like Amazon Video can switch from Silverlight to encrypted HTML5 video.

  • Enable VP9 video codec for users with fast machines

  • Embedded YouTube videos now play with HTML5 video if Flash is not installed.

  • Allow no-cache on back/forward navigations for https resources

  • Latgalu [ltg] locale added. Wikipedia tells us there are 164,500 daily speakers.

  • View and search open tabs from your smartphone or another computer in a sidebar



  • FUEL (Firefox User Extension Library) has been removed. Add-ons relying on it will stop working.

  • The browser.sessionstore.restore_on_demand preference has been reset to its default value (true) to avoid e10s performance problems. Because faster is better!

  • The Firefox click-to-activate plugin whitelist has been removed.

  • XRender is no longer used for rendering web content on Linux as this may cause a regression in remote X performance


  • Smart multi-line input in the Web Console

  • Custom user agents supported in Responsive Design Mode

  • Simulate Push messages in the Service Workers developer tool

  • View, start,and debug registered Service Workers in the Service Workers developer tool

  • 'Start' button for service workers in about:debugging to start registered Service Workers

  • Added support for ChaCha20/Poly1305 cipher suites

  • Changes that can affect add-on compatibility

Web Platform

  • WebCrypto: RSA-PSS signature support

  • WebCrypto: PBKDF2 supports SHA-2 hash algorithms

  • cuechange events are now available on TextTrack objects


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