Firefox Developer Edition
Release Notes

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

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

BroadcastChannel API implemented

Implemented srcset attribute and <picture> element for responsive images

Implemented DOM3 Events KeyboardEvent.code

Mac OS X: Implemented a subset of the Media Source Extensions (MSE) API to allow native HTML5 playback on YouTube

Implemented Encrypted Media Extensions (EME) API to support encrypted HTML5 video/audio playback (Windows Vista or later only)

Automatically download Adobe Primetime Content Decryption Module (CDM) for DRM playback through EME (Windows Vista or later only)