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 Release

July 2, 2015

Version 39.0, first offered to Release channel users on July 2, 2015

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



  • Improve performance of IPv6 fallback to IPv4

  • Fix incomplete downloads being marked as complete by detecting broken HTTP1.1 transfers

  • A regression that could lead to Flash not displaying has been fixed

  • Security state indicator on a page now correctly ignores loads caused by previous pages

  • Fixed an issue where a Hello conversation window would sometimes fail to open

  • Various security fixes


  • Removed support for insecure SSLv3 for network communications

  • Performance of displaying dashed lines is improved (Mac OS X)

  • Malware detection service for downloads now covers common Mac file types


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

  • localhost is now available offline for WebSocket connections

  • Drag and drop enabled for nodes in Inspector markup view

  • Web Console input history persists even after closing the toolbox

Developer Information