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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.

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Firefox Release

March 18, 2014

Version 28.0, first offered to Release channel users on March 18, 2014

Thanks to our contributors linkCheck out "What’s New" and "Known Issues" for this version of Firefox below. As always, you’re encouraged to tell us what you think, or file a bug in Bugzilla.

We'd also like extend a special thank you to all of the new Mozillians who contributed to Firefox 28!!


  • VP9 video decoding implemented

  • Mac OS X: Notification Center support for web notifications

  • Horizontal HTML5 audio/video volume control

  • Support for Opus in WebM



  • Now that spdy/3 is implemented support for spdy/2 has been removed and servers without spdy/3 will negotiate to http/1 without any penalty


  • Support for MathML 2.0 'mathvariant' attribute

  • Background thread hang reporting

  • Support for multi-line flexbox in layout

Developer Information


  • Text Rendering Issues on Windows 7 with Platform Update KB2670838 (MSIE 10 Prerequisite) or on Windows 8.1 has a workaround (see 812695)

  • Echo cancellation on fails (974537)