To test the latest developer features of Firefox, install Firefox Developer Edition Firefox 48 was released on August 2, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
- The position of elements can now be changed within the content (Firefox bug 1139187).
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).
<summary>elements have been activated by default on Nightly and Aurora (DevTools), but not on Beta or Release:
metaattributes now also supports the
origin-when-cross-originvalues (Firefox bug 1178337).
calc()has been improved to be closer to the specification:
- Our experimental implementation of CSS grids has been updated:
mask-modehas been added; the
autovalue has been renamed to
match-source, to match the spec (Firefox bug 1228354).
- Interpolation of
clip-pathbasic 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
allvalue of the
text-combine-uprightproperty (Firefox bug 1097499).
- Support for the experimental
color-adjustproperty has been added, allowing pages to specify that background colors and images should be printed (Firefox bug 1209273).
::first-letterpseudo-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).
-webkitprefixed properties and values have been added for web compatibility, behind the preference
layout.css.prefixes.webkit, defaulting to
-webkit-text-fill-color(Firefox bug 1247777).
-webkit-text-stroke-width(Firefox bug 1248708).
-webkit-background-clip(as background-clip) text value (Firefox bug 759568).
-webkit-box-orient(Firefox bug 1262049.
- The value
-webkit-inline-boxis now an alias of
displayproperty. (Firefox bug 1257661).
-webkit-align-contentwere added as aliases for the unprefixed properties and the values
displayproperty as aliases for the unprefixed values (Firefox bug 1274096).
displayas aliases for modern CSS Flexbox (Firefox bug 1208635).
background-clipis now available in all type of Firefox (and not only non-release builds) (Firefox bug 1263516).
positionproperties on the top layer element (Firefox bug 1236828).
- Added an internal-only syntax for
@supportsto detect pref (Firefox bug 1259889).
String.prototype.padEnd()methods have been implemented (Firefox bug 1260509).
- The ES2015
Array.prototype[@@unscopables]properties have been implemented (Firefox bug 1054759 and Firefox bug 1258163).
- The ES2015
Symbol.isConcatSpreadablesymbol has been implemented (Firefox bug 1041586).
- The ES2015
Array[@@species]getter has been implemented (Firefox bug 1165052).
- The ES2015
%TypedArray%[@@species]getter have been implemented (Firefox bug 1165053).
Intl.getCanonicalLocales()method of the ECMAScript Internationalization API draft has been implemented (Firefox bug 1263040).
Deprecations and removals
- The deprecated old Proxy API (
Proxy.createFunction()) has been removed. Use the standard
Proxyobject instead (Firefox bug 892903).
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.prototype.multiline) has been removed. Use the standard m flag instead (Firefox bug 1219757).
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
CSSKeyframesRuleinterfaces (Firefox bug 1256178).
NavigatorConcurrentHardwaremixin has been implemented, which adds the
Navigator.hardwareConcurrencyproperty to the
Navigatorinterface. This lets websites and apps get at least an approximation of how many processing cores are available to run
Workers in (Firefox bug 1008453).
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
Element.animate()is now activated by default (Firefox bug 1245000).
- The two methods
Element.insertAdjacentElement()have been implemented (Firefox bug 811259).
Document.scrollingElementgot enabled by default (Firefox bug 1265032).
Node.prefixwere moved to the
AttrAPIs (Firefox bug 1055776).
- Per the latest specification, the values of
KeyboardEvent.codereturned for the following keys have been changed see (Firefox bug 1264150):
"IntlHash"has been removed.
- All keys whose
codevalues were reported as "" in earlier versions of Firefox are now reported as "Unidentified".
- The two methods
MediaStreamTrack.clone()have been implemented (Firefox bug 1208371).
iceRestartentry is now supported in the
RTCOfferOptionscode dictionary, allowing
createOffer()to be used to request ICE restarts (Firefox bug 906986).
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
MediaRecordercan now be played back successfully.
- The Web Crypto API is now available in Web workers (Firefox bug 842818).
CustomEventinterface is now available in Web Workers (Firefox bug 1003432).
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 —
MozSettingsEvent(see Firefox bug 1043562, Firefox bug 1256414, and Firefox bug 1256046).
- Support for UTF-16 has been removed from
TextEncoder(Firefox bug 1257877).
RTCStatsReportis now a true
maplikeinterface: in addition to
has(), the methods
keys(), as well as the
sizegetter have been implemented (Firefox bug 906986).
Request.cacheproperty 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
keypressevent 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
"Dead"for dead keypresses which don't generate text in other situations.
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