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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

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

  • 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


  • 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

Developer Information

Web Platform