install Firefox Developer Edition Firefox 42 was released on November 3, 2015. 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.
Changes for Web developers
- Debugging Firefox for Android over Wifi
- Firefox OS Simulator configuration in WebIDE
- CSS filter presets
writing-modeis now supported with rtl scripts (bug 1131451).
- The values of
caption-sideare now relative to the table, and changing actual meaning according to its
writing-modevalue bug 1202993.
- Non-standard properties like
-moz-margin-startare now aliases of their standard counterpart (
margin-inline-start, …). Previously, it was the opposite. This affects the value returned by
CSSStyleDeclaration.cssTextand iteration of the properties in a style ruleand iteration of the properties in a style rule, that both use the canonical form (bug 1118103).
- The prefixed version of CSS gradients can be turned off by setting the
- Several old bugs with
floatand margin collapsing behavior have been fixed (bug 478834, bug 538194, and bug 451791).
- Experimental support for the
referrerattribute of the
<area>(bug 1174913) has been added. There is no effect by default, the
Reflectobject has been implemented (bug 987514).
- The implementation of the
handler.ownKeys()trap has been updated to match the final ES2015 specification (bug 1049662).
new, will now throw a
DOM & HTML DOM
- Images with an
idare no more listed as property of the
<img id="login">isn't accessible as
window.loginanymore. This behavior was introduced in Firefox 26 and has been removed to match a later change in the spec. (bug 959992)
MouseEvent.offsetYhave been added (bug 69787).
HTMLInputElementinterface has been experimentally extended to handle the upload of directories (bug 1164310). These four members can be exposed by setting the
Directoryinterface has been experimentally extended (bug 1177688). The two members
Directory.getContentscan be exposed by setting the
HTMLMediaElement.mozSrcObjecthas been renamed in
Request.contexthas been removed (bug 1188062).
- The Push API has been activated by default on Firefox for Desktop (bug 1153499), but only on the Nightly/Dev Edition/Beta channels. It is being deactivated by default in the Release channel until consumer UX and debugging features have been properly implemented (bug 1208560.) You can still activate it by enabling the
dom.push.enabledpref in about:config.
PushManager.hasPermission()method has been deprecated in the spec, and replaced with the
PushManager.permissionState()method. Firefox has updated its implementation to reflect this (bug 1183853.)
- Service-worker-related additions to the Notifications API have been implemented (bug 1114554), but are disabled in this release.
Web Animations API
Our experimental implementation of Web Animations API have been extended to support:
AnimationPlayer.playbackRateproperty (bug 1127380).
CSSTransitioninterfaces (bug 1178186).
Animation.reverse()method (bug 1150808).
AnimationPlaybackEventinterface has been added and
finishare now fired on
Our experimental implementation of the Shadow DOM has been modified:
- When trying to invoke
ShadowRoot, throws a
DataCloneErrorexception (bug 1176757).
- When invoking
ShadowRootas an argument, we now throws a
NotSupportedErrorexception (bug 1177914).
- When invoking
ShadowRootas an argument, we now throws a
HierarchyRequestErrorexception (bug 1177991).
WebGLTransformFeedbackhas been implemented (bug 1048724).
- To obtain a WebGL2 context,
RTCPeerConnection.createOffer()'s options data type,
RTCOfferOptions, has been updated to more closely match the specification. Among other changes, it is now based upon the
RTCOfferAnswerOptionsdictionary, which provides the
RTCAnswerOptionsdictionary has been added. This is the type used for the
RTCICECandidatePairStats.mozPriorityhas been renamed to
ImageBitmapinterface and the
createImageBitmap()method have been implemented. They are available on regular window scripts and in Web workers and allow efficient posting of images between window and worker contexts (bug 1044102).
IDBCursorWithValueinterface is now available in Web workers (bug 1188115).
- Error events sent in Web workers doesn't bubble anymore (bug 1188141).
- Media Source Extensions (MSE) has been activated for all Web sites, and no more for a white list of sites (bug 1185611).
- The non-standard and deprecated
Window.mozRequestAnimationFrame()has been removed (bug 909154). Use the standard
- Speech synthesis (text-to-speech) has been implemented in Firefox Desktop for Windows, hidden behind the
about:config(bug 1003457.) See Web Speech API for more information.
- Firefox 41 and earlier versions were incorrectly accepting undefined or invalid pseudo-header fields in HTTP/2 responses. This is now fixed and the only pseudo-header field accepted from Firefox 42 is the :status as per the specification. Response headers containing arbitrary fields are considered malformed. (bug 1136727)
- EV certificates with a validity greater than 39 months are now considered and handled as DV certificates (bug 1145679).
Changes for add-on and Mozilla developers
TYPE_EMBEDconstant has been added to
nsIContentPolicyto allow Gecko internals and add-on code to better differentiate different types of requests. Previously,
TYPE_OBJECTwas used for these cases (bug 1148030).
- Similarly, the
TYPE_SUBDOCUMENTconstants has been split into
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