Firefox Developer Edition

February 27, 2015

Version 38.0a2, first offered to Firefox Developer Edition channel users on February 27, 2015

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


  • 64bit Windows builds (download here)

  • New tab-based preferences

  • Share the active tab or window in a Hello conversation - enabled for first half of the beta cycle

  • Keep track of articles and blog posts with the Reading List - enabled for the first half of the beta cycle

  • Ruby annotation support


  • autocomplete=off is no longer supported for username/password fields

  • URL parser avoids doing percent encoding when setting the Fragment part of the URL, and percent decoding when getting the Fragment in line with the URL spec

  • RegExp.prototype.source now returns "(?:)" instead of the empty string for empty regular expressions

  • Improved page load times via speculative connection warmup


  • Developer Information
  • Optimized-out variables are now visible in Debugger UI

  • XMLHttpRequest logs in the web console are now visually labelled and can be filtered separately from regular network requests

  • WebRTC now has multistream and renegotiation support

  • copy command added to console

Web Platform

All Firefox Developer Edition downloads