To test the latest developer features of Firefox,
install Firefox Developer EditionFirefox 44 was released on January 26, 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.
Changes for Web developers
Developer tools
Highlights:
- Memory tool
- Animation inspector improvements
- New Waterfall markers: DomContentLoaded, load, worker messages
All devtools bugs fixed between Firefox 43 and Firefox 44.
HTML
<link rel="prefetch">
now obeys thecrossorigin
attribute (bug 1214819).
CSS
position:
fixed;
now always creates a new stacking context (bug 1179288).- The support of
unicode-range
has been enabled by default (bug 1119062). - Our experimental implementation of CSS Writing Modes has been updated to reflect the latest specification:
- The value
sideways
of thetext-orientation
property has been implemented andsideways-right
has been made an alias of it (bug 1193488). - The value
sideways-rl
andsideways-lr
of thewriting-mode
property (bug 1193488 and bug 1193519).
- The value
- The non-standard properties
-moz-math-display
and-moz-window-shadow
are no more available from Web content (bug 1207002, bug 1211040, and bug 1212607). - The
font-style
property now distinguishes betweenoblique
anditalic
when both variants are available (bug 543715). - Though not supported, the properties
marks
,orphans
,page
,size
, andwidows
, were parsed and@supports
was incorrectly reporting them as supported; this has been fixed and the properties are not parsed anymore, nor marked as supported (bug 1215702). - The internal value
-moz-mac-unified-toolbar
has been removed from the possible values for the-moz-appearance
property (bug 1206468). - Several
-webkit
prefixed properties and values have been added for web compatibility, behind the preferencelayout.css.prefixes.webkit
, defaulting tofalse
(bug 837211):-webkit-animation
-webkit-animation-delay
-webkit-animation-direction
-webkit-animation-duration
-webkit-animation-fill-mode
-webkit-animation-iteration-count
-webkit-animation-name
-webkit-animation-play-state
-webkit-animation-timing-function
-webkit-text-size-adjust
-webkit-transform
-webkit-transform-origin
-webkit-transform-style
-webkit-transition
-webkit-transition-delay
-webkit-transition-duration
-webkit-transition-property
-webkit-transition-timing-function
-webkit-border-radius
-webkit-border-top-left-radius
-webkit-border-top-right-radius
-webkit-border-bottom-left-radius
-webkit-border-bottom-right-radius
-webkit-appearance
-webkit-background-clip
-webkit-background-origin
-webkit-background-size
-webkit-border-image
-webkit-box-shadow
-webkit-box-sizing
-webkit-user-select
-webkit-linear-gradient()
bug 1210575-webkit-radial-gradient()
bug 1210575-webkit-repeating-linear-gradient()
bug 1210575-webkit-repeating-radial-gradient()
bug 1210575
JavaScript
New APIs
Symbol.toPrimitive
,Symbol.prototype[@@toPrimitive]
, andDate.prototype[@@toPrimitive]
have been implemented (bug 1054756).
Changes
- The
let
andconst
bindings in the global level have been made compliant with ES2015 semantics. See bug 589199 and the blog post "Breaking changes in let and const in Firefox Nightly 44". In addition,let
is now available to default Web JavaScript (strict and non-strict) and does not require a version opt-in anymore (bug 932517). - If typed arrays' (like
Int8Array
) andArrayBuffer
) constructors are called as a function without thenew
operator, aTypeError
is now thrown as per the ES2015 specification (bug 980945, bug 1214936). - The
RegExp
sticky flag now follows the ES2015 standard for anchored sticky regular expressions (bug 773687). - The JavaScript shell (SpiderMonkey's REPL) now defaults to the default, Web-compatible JS version (and not JS1.7+ anymore) (bug 1192329).
Removals
- Support for the non-standard
let
blocks has been dropped (bug 1167029. - The non-standard and deprecated property
Object.prototype.__noSuchMethod__
has been removed (bug 683218).
Interfaces/APIs/DOM
DOM & HTML DOM
- For compatibility with specific existing sites, the property
Document.charset
has been implemented as an alias ofDocument.characterSet
(bug 647621). - Support for the
window.sidebar.addSearchEngine()
method, which allowed Web pages to invoke an installation of a Sherlock plugin, has been dropped and now it just logs a warning in the Web Console (bug 862148). - To fight unwanted pop-ups, prompts requested in
Window.onbeforeunload
of pages that have not been interacted with are no more displayed (bug 636905). - The deprecated method
MessageEvent.initMessageEvent()
has been reimplemented for backward compatibility (bug 949376). - The obsolete property
DocumentType.internalSubset
has been removed (bug 801545). - For compatibility with existing sites, the properties
Window.orientation
andWindow.onorientationchange
, as well as theorientationchange
event have been implemented (bug 920734). - An
<iframe>
with explicit fullscreen request should not exit fullscreen implicitly (bug 1187801). - The events
mouseover
,mouseout
,mouseenter
,mouseleave
,pointermove
,pointerover
,pointerout
,pointerenter
andpointerleave
are now triggered for disabled form elements (bug 218093). - The method
Element.webkitMatchesSelector()
has been added (bug 1216193) to improve interoperability. - To match the spec, the method
Document.createAttribute()
now converts the input to lower case (bug 1176313). - The non-standard
dialog
feature forWindow.open()
is no longer available to Web content. It is still available to extensions and other code with chrome privileges (bug 1095236.
Canvas
- A new experimental
OffscreenCanvas
API that allows rendering contexts (such as WebGL) to run in Web Workers has been implemented. To use this experimental API setgfx.offscreencanvas.enabled
totrue
in about:config (bug 709490). This API includes:- The
OffscreenCanvas
interface, HTMLCanvasElement.transferControlToOffscreen()
, andWebGLRenderingContext.commit()
.- Several WebGL interfaces are now also available in a worker context when this API is enabled.
- The
WebGL
- Uniform Buffer Objects have been implemented (bug 1048747).
IndexedDB
- The
IDBIndex.getAll()
andIDBIndex.getAllKeys()
, and there counterparts onIDBObjectStore
are now available by default (bug 1196841).
Service Workers
- The
ServiceWorkerMessageEvent
andExtendableMessageEvent
interfaces have been implemented (bug 1143717 and bug 1207068). Headers
objects now support a pair iterator, meaning that the methodsHeaders.entries()
,Headers.keys()
, andHeaders.values()
are now available;Symbol.iterator
now also returns the default iterator for them (bug 1108181).- The
XMLHttpRequest
API has been disabled on Service Workers (bug 931243). - The interface
FetchEvent
now extendsExtendableEvent
, giving it access to theExtendableEvent.waitUntil()
method. (bug 1214772). - Following a recent change in the specification,
FetchEvent.client
has been removed (bug 1218135). - To match the latest specification, the
ServiceWorkerContainer.onreloadpage
has been removed (bug 1218139). - The event handlers
ServiceWorkerGlobalScope.onbeforeevicted
andServiceWorkerGlobalScope.onevicted
have been removed as they weren't following the spec. They will be reintroduced in the future, but their removal will allow feature detection to work as expected (bug 1218142). - In the
FetchEvent()
constructor, if theisReload
member is not present in the options dictionary, it now defaults tofalse
(bug 1216401). - The
Client.frameType
property is now implemented on the right interface; it was onWindowClient
before (bug 1218146). - When AppCache is used to provide offline support for a page, a warning message is now displayed in the console advising developers to use Service workers instead (bug 1204581.)
- Service workers have been enabled by default in Gecko.
WebRTC
- WebRTC interfaces have been unprefixed (bug 1155923). In particular:
mozRTCPeerConnection
is nowRTCPeerConnection
.mozRTCIceCandidate
is nowRTCIceCandidate
.mozRTCSessionDescription
is nowRTCSessionDescription
.
- The
RTCDataChannel.bufferedAmountLowThreshold
andRTCDataChannel.onbufferedamountlow
properties, as well as thebufferedamountlow
event, have been implemented (bug 1178091). - The attribute
RTCPeerConnection.canTrickleIceCandidates
has been added, the non-standard methodRTCPeerConnection.updateIce()
removed (bug 1209744). - The
MediaStream
interface now supports theMediaStream.addTrack()
andMediaStream.removeTrack()
methods (bug 1103188). - The constructor
MediaStream()
has been implemented (bug 1070216). - Support for the non-standard constraint style option list for
RTCOfferOptions
has been removed; see this post on the site compatibility blog for details.
New APIs
- An experimental implementation of the Canvas API in Workers has landed:
OfflineCanvas
andHTMLCanvasElement.transferControlToOffscreen()
are available behind thegfx.offscreencanvas.enabled
preference, currently disabled by default (bug 709490). - The Text2Speech API, part of Web Speech API, has now an OS X backend. But this is disabled by default (bug 1003452).
Miscellaneous
URLSearchParams
objects now support a pair iterator, meaning that the methodsURLSearchParams.entries()
,URLSearchParams.keys()
, andURLSearchParams.values()
are now available;Symbol.iterator
now also returns the default iterator for them (bug 1085284).FormData
objects now support a pair iterator, meaning that the methodsFormData.entries()
,FormData.keys
, andFormData.values()
are now available;Symbol.iterator
now also returns the default iterator for them (bug 1127703).- When
XMLHttpRequest.send()
is used with an HTML document, it now usestext/html
instead ofapplication/xml
(bug 918771). - Speech synthesis (text-to-speech) has been implemented in Firefox Desktop for Mac and Linux, hidden behind the
media.webspeech.synth.enabled
flag inabout:config
(bug 1003452, bug 1003464.) See Web Speech API for more information. - Elements inside a
<frame>
or an<object>
can't be set full-screen anymore (bug 1212299). - Sanitization of WOFF fonts is a bit more stricter, leading to more incorrect fonts being rejected, this sanitization is made a bit less stricter in Firefox 46 (bug 1193050 and bug 1244693).
MathML
No change.
SVG
No change.
Audio/Video
No change.
HTTP
- Support for the Brotli algorithm has been added and both
Accept-Encoding
andContent-Encoding
headers now support thebr
value (bug 366559 and bug 1211916). - Incorrect support of HTTP/2 headers containing line breaks (
'/n'
) have been removed as the spec doesn't allow it, unlike HTTP/1 (bug 1197847).
Networking
No change.
Security
- RC4 is now also disabled by default on Beta and Release versions of the browser (bug 1201025) and the whitelist is now empty by default (bug 1215796).
Changes for add-on and Mozilla developers
Interfaces
No change
XUL
No change.
JavaScript code modules
- Added
LIKE
support to {JSM("Sqlite.jsm")}} (bug 1188760). - Added Snackbars.jsm module to Firefox for Android (bug 1215026)
XPCOM
- The
nsIDOMWindow
interface is now empty. Its contents were either no longer used, had moved elsewhere, or were only used from C++. The items available from C++ code now reside in thensPIDOMWindow
interface (bug 1216401).
Other
- Due to breaking changes in Firefox 44 (bug 1202902), add-ons packed with cfx will not work any longer. To make your add-on compatible again, please use jpm. You can find steps to migrate from cfx to jpm here.
See also
Older versions
- Firefox 43 for developers
- Firefox 42 for developers
- Firefox 41 for developers
- Firefox 40 for developers
- Firefox 39 for developers
- Firefox 38 for developers
- Firefox 37 for developers
- Firefox 36 for developers
- Firefox 35 for developers
- Firefox 34 for developers
- Firefox 33 for developers
- Firefox 32 for developers
- Firefox 31 for developers
- Firefox 30 for developers
- Firefox 29 for developers
- Firefox 28 for developers
- Firefox 27 for developers
- Firefox 26 for developers
- Firefox 25 for developers
- Firefox 24 for developers
- Firefox 23 for developers
- Firefox 22 for developers
- Firefox 21 for developers
- Firefox 20 for developers
- Firefox 19 for developers
- Firefox 18 for developers
- Firefox 17 for developers
- Firefox 16 for developers
- Firefox 15 for developers
- Firefox 14 for developers
- Firefox 13 for developers
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