Firefox 31 (July 2014)

  • CSS: variables

Firefox 30 (June 2014)

  • CSS: Allow line-height in <input type='button'>
  • JS: Console.count()
  • JS: ES6 array and generator comprehensions

Firefox 29 (April 2014)

  • New UI
  • CSS: Unprefixed box-shadow

Firefox 18 (Jan 2013)

  • Faster JS compiler (IonMonkey)
  • Mac retina support
  • JS: window.devicePixelRatio
  • JS: unprefixed ontouchstart
  • HTML: <input type='number'>
  • HTML: <input type='color'>

Firefox 17 (Nov 2012)

  • No more support for Mac OSX 10.5 and below
  • SVG FillPaint and StrokePaint
  • HTML <iframe sandbox=...> (docs)
  • Official support for Windows 8 (link)

Firefox 16 (Oct 2012)

  • Web app support (docs)
  • Unprefixed CSS animations, transitions, transforms, gradients

Firefox 15 (Aug 2012)

  • Background updates
  • SPDY v3
  • Opus audio codec
  • HTML <audio played> (and <video>)
  • HTML <source media=...>

Firefox 14 (Jul 2012)

  • Full screen support for OSX Lion
  • JS pointer lock API (docs)
  • JS display sleep API (docs)

Firefox 13 (Jun 2012)

  • Smooth scrolling by default
  • SPDY on by default
  • CSS column-fill (docs)
  • ECMA 6 Map and Set
  • CSS background-position extended syntax
  • CSS :invalid
  • CSS turn unit (rotate(0.5turn))

Firefox 12 (Apr 2012)

  • CSS text-align-last (docs)

Firefox 11 (Mar 2012)

  • element.outerHTML (docs)
  • Dev tools: Style editor, 3D page inspector (docs)
  • Unprefixed web sockets
  • CSS text-size-adjust (docs)

Firefox 10 (Jan 2012)

  • CSS 3D transforms
  • HTML <bdi> element
  • JS fullscreen API (docs)
  • IndexedDB APIs
  • Dev tools: CSS Style inspector

Firefox 9 (Dec 2011)

  • Two-finger swipe in Mac OSX Lion
  • CSS font-stretch
  • CSS improved text-overflow
  • JS navigator.doNotTrack

Firefox 8 (Nov 2011)

Firefox 7 (Sep 2011)

  • CSS text-overflow: ellipsis
  • Hidden http:// prefix in address bar

Firefox 6 (Aug 2011)

  • JS window.matchMedia
  • Websockets (!)
  • JS EvetnSource / server-sent events

Firefox 5 (Jun 2011)

  • CSS animations
  • Background tab setTimeout and setInterval clamped to 1000ms

Firefox 4 (Mar 2011)

  • Do Not Track (DNT) header
  • New JS endinge (JagerMonkey)
  • Hardware-accelerated rendering
  • WebM video
  • OpenType ligatures/kerning/font variants
  • CSS transitions partial support
  • JS audio data API
  • JS mozRequestAnimationFrame
  • HTML5 forms API
  • <video buffered>
  • HTML5 history API
  • New HTML5 parser
  • …

Firefox 3.6 (Jan 2010)

  • CSS gradients
  • CSS pointer events
  • HTML drag & drop API
  • HTML <script async>

Reference