Firefox 48 for developers

• The position of elements can now be changed within the content (Firefox bug 1139187).
• Implemented console.clear() to clear the console output (Firefox bug 659625).
• Added HTTP log inspection to the Web Console (Firefox bug 1211525).
• Added a Firebug theme (Firefox bug 1244054).
• Added the DOM Inspector (Firefox bug 1201475).
• Font inspector has been enabled by default again (Firefox bug 1280121).
• Improved suggestions for CSS properties (Firefox bug 1168246).
• Cookies, localstorage and sessionstorage entries are editable via double-click (Firefox bug 1231154, Firefox bug 1231179, Firefox bug 1231155).

• The <details> and <summary> elements have been activated by default on Nightly and Aurora (DevTools), but not on Beta or Release:
  • The default style for these elements has been adapted to match the spec (Firefox bug 1258657).
  • The toggle event is now sent to the <details> element when this one is opened or closed (Firefox bug 1225412).
• The meta attributes now also supports the no-referrer-when-downgrade and origin-when-cross-origin values (Firefox bug 1178337).

• The calc() has been improved to be closer to the specification:
  • calc() is now supported on the line-height property (Firefox bug 594933).
  • Added support for nested CSS calc() (Firefox bug 968761).
• Our experimental implementation of CSS grids has been updated:
  • Fragmentation for grid layout has been implemented (Firefox bug 1144096).
  • [css-grid] Percentage tracks are now treated as auto if grid container size is indefinite (Firefox bug 1264607).
  • <fieldset> now supports grid and flex layouts (Firefox bug 1230207).
• The luminance value for mask-mode has been added; the auto value has been renamed to match-source, to match the spec (Firefox bug 1228354).
• Interpolation of clip-path basic shapes in CSS animations and transitions is now supported (Firefox bug 1110460).
• Support for horizontal-in-vertical (tate-chu-yoko) text has been added via the all value of the text-combine-upright property (Firefox bug 1097499).
• Support for the experimental color-adjust property has been added, allowing pages to specify that background colors and images should be printed (Firefox bug 1209273).
• The ::first-letter pseudo-element now also matches punctuation characters of type Pd that precede or immediately follow the actual first letter; this is a new requirement of CSS Pseudo-element module level 4 (Firefox bug 1260366).
• Several -webkit prefixed properties and values have been added for web compatibility, behind the preference layout.css.prefixes.webkit, defaulting to false:
  • -webkit-text-fill-color (Firefox bug 1247777).
  • -webkit-text-stroke, -webkit-text-stroke-color, -webkit-text-stroke-width (Firefox bug 1248708).
  • -webkit-background-clip (as background-clip) text value (Firefox bug 759568).
  • -webkit-box-direction, -webkit-box-orient (Firefox bug 1262049.
  • The value -webkit-inline-box is now an alias of inline-flex on the display property. (Firefox bug 1257661).
  • -webkit-flex-direction, -webkit-flex-wrap, -webkit-flex-flow, -webkit-order, -webkit-flex, -webkit-flex-grow, -webkit-flex-shrink, -webkit-flex-basis, -webkit-justify-content, -webkit-align-items, -webkit-align-self and -webkit-align-content were added as aliases for the unprefixed properties and the values -webkit-flex and -webkit-inline-flex for the display property as aliases for the unprefixed values (Firefox bug 1274096).
  • Added -webkit-box-flex, -webkit-box-ordinal-group, -webkit-box-align and -webkit-box-pack properties and -webkit-box value to display as aliases for modern CSS Flexbox (Firefox bug 1208635).
• The text value of background-clip is now available in all type of Firefox (and not only non-release builds) (Firefox bug 1263516).
• The absolute value of position properties on the top layer element (Firefox bug 1236828).
• Added an internal-only syntax for @supports to detect pref (Firefox bug 1259889).

New APIs

• The String.prototype.padStart() and String.prototype.padEnd() methods have been implemented (Firefox bug 1260509).
• The ES2015 Symbol.unscopables and Array.prototype[@@unscopables] properties have been implemented (Firefox bug 1054759 and Firefox bug 1258163).
• The ES2015 Symbol.isConcatSpreadable symbol has been implemented (Firefox bug 1041586).
• The ES2015 Array[@@species] getter has been implemented (Firefox bug 1165052).
• The ES2015 ArrayBuffer[@@species] getter and %TypedArray%[@@species] getter have been implemented (Firefox bug 1165053).
• The Intl.getCanonicalLocales() method of the ECMAScript Internationalization API draft has been implemented (Firefox bug 1263040).

Deprecations and removals

• The deprecated old Proxy API (Proxy.create and Proxy.createFunction()) has been removed. Use the standard Proxy object instead (Firefox bug 892903).
• The String.prototype.contains() method has been removed (it was deprecated since version 40). Use the String.prototype.includes() method instead (Firefox bug 1103588).
• The non-standard RegExp.multiline property (not RegExp.prototype.multiline) has been removed. Use the standard m flag instead (Firefox bug 1219757).
• The Object.prototype.__defineGetter__() and Object.prototype.__defineSetter__() methods can no longer be called at the global scope without any object. (Firefox bug 1253016).

DOM & HTML DOM

• Dropped the "Moz" prefix from the CSSKeyframeRule and CSSKeyframesRule interfaces (Firefox bug 1256178).
• The NavigatorConcurrentHardware mixin has been implemented, which adds the Navigator.hardwareConcurrency property to the Navigator interface. This lets websites and apps get at least an approximation of how many processing cores are available to run Workers in (Firefox bug 1008453).
• The Node.isSameNode() method, which was removed in Firefox 10, has returned after being added back into the specification after a lengthy absence (Firefox bug 1256299).
• Firefox now returns proper exceptions instead of numbers when things go wrong during a call to Navigator.registerProtocolHandler().
• Element.animate() is now activated by default (Firefox bug 1245000).
• The two methods Element.insertAdjacentText() and Element.insertAdjacentElement() have been implemented (Firefox bug 811259).
• Document.scrollingElement got enabled by default (Firefox bug 1265032).
• Node.localName, Node.namespaceURI and Node.prefix were moved to the Element and Attr APIs (Firefox bug 1055776).
• Per the latest specification, the values of KeyboardEvent.code returned for the following keys have been changed see (Firefox bug 1264150):
  • "OSLeft" and "OSRight" are now "MetaLeft" and "MetaRight".
  • "VolumeDown", "VolumeUp", and "VolumeMute" are now "AudioVolumeDown", "AudioVolumeUp", and "AudioVolumeMute".
  • "IntlHash" has been removed.
  • All keys whose code values were reported as "" in earlier versions of Firefox are now reported as "Unidentified".

Canvas 2D

• The CanvasRenderingContext2D.ellipse() method has been implemented (Firefox bug 910138).

WebRTC

• The two methods MediaStream.clone() and MediaStreamTrack.clone() have been implemented (Firefox bug 1208371).
• The iceRestart entry is now supported in the RTCOfferOptions code dictionary, allowing createOffer() to be used to request ICE restarts (Firefox bug 906986).
• The RTCPeerConnection.createOffer() method now prefers the VP9 video codec by default; previously VP8 was preferred (Firefox bug 1242324.
• WebM/VP8 video that includes video resolution changes that has been recorded using MediaRecorder can now be played back successfully.

Others

• The Web Crypto API is now available in Web workers (Firefox bug 842818).
• The CustomEvent interface is now available in Web Workers (Firefox bug 1003432).
• The DOMApplicationsManager.getNotInstalled() method has been removed (Firefox bug 1255036).
• Several Firefox OS APIs that were erroneously exposed to the Web have now been hidden as they should have been — mozContact, MozContactChangeEvent, navigator.mozContacts, MozPowerManager, MozSettingsEvent (see Firefox bug 1043562, Firefox bug 1256414, and Firefox bug 1256046).
• Support for UTF-16 has been removed from TextEncoder (Firefox bug 1257877).
• RTCStatsReport is now a true maplike interface: in addition to forEach(), get(), and has(), the methods entries(), values(), keys(), as well as the size getter have been implemented (Firefox bug 906986).
• The Request.cache property has been added allowing to control the cache behavior (Firefox bug 1120715).
• Handling of dead keys on Mac OS X has been changed to work the same as other platforms; they no longer fire a keypress event when no text is generated when the focused element isn't editable (when the focused element is editable, dead key causes composition events instead of keyboard events on Mac OS X). Also, like on other platforms, the value of KeyboardEvent.key is now "Dead" for dead keypresses which don't generate text in other situations.

• Support for the Upgrade-Insecure-Requests header has been added (Firefox bug 1243586).
• The block-all-mixed-content CSP directive has been implemented (Firefox bug 1122236)

• The Social Worker API has been removed.
• Added the -moz-bool-pref() CSS @supports function to allow hiding portions of chrome stylesheets behind boolean preferences. (Firefox bug 1259889)