Firefox Developer Edition
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.

Firefox Developer Edition

April 3, 2015

Version 39.0a2, first offered to Firefox Developer Edition channel users on April 3, 2015

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



  • Improve performance of IPv6 fallback to IPv4


  • Removed support for insecure SSLv3 for network communications

  • Disable use of RC4 except for temporarily whitelisted hosts

  • NPAPI Plug-in performance improved via asynchronous initialization


  • Drag and drop enabled for nodes in Inspector markup view

  • Web Console input history persists even after closing the toolbox

  • Cubic bezier tooltip now shows a gallery of timing-function presets for use with CSS animations

  • localhost is now available offline for WebSocket connections

Web Platform

Get the most recent version

All Firefox Developer Edition downloads