See what’s new in Firefox!

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.


Firefox Developer Edition

December 5, 2014

Version 36.0a2, first offered to Firefox Developer Edition channel users on December 5, 2014

For more information about Developer Edition please see this MDN article and also this post.


  • Pinned tiles on the new tab page can be synced

  • Support for the full HTTP/2 protocol. HTTP/2 enables a faster, more scalable, and more responsive web.



  • No longer accept insecure RC4 ciphers whenever possible

  • -remote option removed

  • Shut down hangs will now show the crash reporter before exiting the program


  • Inspector: More paste options in markup view

  • DOM Promises inspection

  • Eval sources now appear in the Debugger
    Debug JavaScript code that is evaluated dynamically, either as a string passed to eval() or as a string passed to the Function constructor

  • WOFF2 fonts are now supported (on Aurora and Nightly)

Developer Information


  • Implemented a subset of the Media Source Extensions (MSE) API to allow native HTML5 playback on YouTube (Windows Vista or later only)

  • Changed JavaScript 'const' semantics to conform better to the ES6 specification.
    The const declaration is now block-scoped and requires an initializer. It also can not be redeclared anymore.

  • Improved ES6 generators for better performance

  • CSS3 will-change property implemented.
    Hints the browser of elements that will be modified. The browser will perform some performance optimization for these

  • isolation CSS property implemented.
    Create a new stacking context to isolate groups of boxes to control which blend together

  • object-fit and object-position implemented.
    Defines how and where the content of a replaced element is displayed

  • CSSOM-View scroll behavior implemented allowing smooth scrolling of content without custom libraries

  • unicode-range CSS descriptor implemented

  • WebSocket now available in Web Workers

  • Support for the ECMAScript 6 Symbol data type added

  • <meta name="referrer"> implemented for more privacy. Allows to control the content of the HTTP referer header.