Firefox 55 for developers
Firefox 55 was released on August 8, 2017. This article lists key changes that are useful for web developers.
Changes for Web developers
- Added filtering of network requests by column values and other properties (Firefox bug 1041895, Firefox bug 1354508, Firefox bug 1354507) and by using regular expressions (Firefox bug 1354495).
- Made it possible to show and hide columns within the Network Monitor (Firefox bug 862855).
- Added remote IP (Firefox bug 1344523), protocol (Firefox bug 1345489), scheme (Firefox bug 1356867), cookies and set cookies columns (Firefox bug 1356869) to Network Monitor.
SourceMapHTTP header is now supported (prior versions supported the deprecated
X-SourceMapheader, see Firefox bug 1346936).
- Elements on which
contenteditablehas been set to
<div>elements to separate different lines of text, to give Firefox parity with other modern browsers (Firefox bug 1297414). See Differences in markup generation for more details.
dom.forms.datetimeby default on Nightly (Firefox bug 1366188).
- Exposed the
transform-boxproperty by default (Firefox bug 1208550).
- Implemented the frames() timing function (Firefox bug 1248340).
- Implemented the
text-justifyproperty (Firefox bug 1343512, Firefox bug 276079).
fit-contentunexpectedly reserves space for full clamp size in
repeat()(Firefox bug 1359060).
clearlogical values —
inline-end— which were previously implemented but preffed off in release channels, are now available in all channels by default (Firefox bug 1253919).
layout.css.variables.enabledpreference has been removed completely meaning that the CSS variables feature is enabled all the time and can no longer be disabled (Firefox bug 1312328).
- Implemented the proprietary
-moz-context-propertiesproperty (Firefox bug 1058040).
- Zero (0) angle value without degree unit is not correctly interpreted in
linear-gradient()(Firefox bug 1363292).
::cuepseudo-element is now supported; it matches on text cues presented within a media element (Firefox bug 1318542).
frattribute has been implemented (Firefox bug 1240275).
- The rest operator (
...) is now supported in object destructuring and the spread operator (
...) now works in object literals (Stage 3 ECMAScript proposal: Object Rest/Spread Properties, Firefox bug 1339395).
- Async generator methods are now supported (Firefox bug 1353693).
String.prototype.toLocaleUpperCase()methods now support an optional
localeparameter to specify a language tag for locale-specific case mappings (Firefox bug 1318403).
Intl.Collatorobject now supports the
caseFirstoption (Firefox bug 866473).
- The Intl API now uses the browser's default locale instead of the operating system's default locale when no locale setting is provided (Firefox bug 1346674).
- Template call sites objects are now canonicalized per realm, based upon their list of raw strings (Firefox bug 1108941).
Float32Array, etc.) have been updated to ES2017. They now use the
ToIndexoperation and allow constructors without arguments, which return zero-length typed arrays (Firefox bug 1317383).
- The Collaborative Scheduling of Background Tasks API (also known as the Background Tasks API or the
requestIdleCallbackAPI) is now enabled by default after being available behind a preference since Firefox 53. This API lets you schedule tasks to be executed when the browser determines that there's free time available before the next repaint occurs, so that your code can make use of that time without causing visible performance lag (Firefox bug 1314959).
- The WebVR 1.1 API is now turned on by default on Windows (and is available on macOS in Nightly). This API exposes virtual reality devices — for example head-mounted displays like the Oculus Rift or HTC Vive — to web apps, enabling developers to translate position and movement information from the display into movement around a 3D scene, and present content into such displays.
- The Intersection Observer API — which provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document's viewport — has been added (Firefox bug 1321865).
scrollY(as well as their aliases
pageYOffset) have been updated to be subpixel precise. Instead of returning an integer, these now return a floating-point value which more accurately describes the scroll position on subpixel-precise displays (Firefox bug 1151421). If need be, you can use
Math.round()to convert them into integers.
MediaQueryList(and other related features) have been updated to match the latest spec. See Firefox bug 1354441, and also see
- Methods of the
DOMTokenListthat modify the list value now automatically trim whitespace and remove duplicate tokens (Firefox bug 869788, also see Trimming of whitespace and removal of duplicates).
URL()constructor can no longer accept a
DOMStringas its base (2nd parameter) — it only accepts a
USVString. It can still use an existing
URLobject for the base, which stringifies itself to the object's
hrefattribute (Firefox bug 1368950).
- The event types supported by the
Document.createEvent()method have been updated as per the latest DOM spec (Firefox bug 1251198).
MessageEvent.originproperty value is now of type
DOMString, and the
MessageEvent.sourceproperty now takes a
MessageEventSourcevalue (which can be a WindowProxy,
ServiceWorkerobject) (Firefox bug 1311324).
- The pinch-to-zoom gesture has now been mapped to the
wheelevent plus the +
Ctrlkey. This mapping was implemented to allow developers to implement simple zooming functionality using the pinch-to-zoom gesture on mobile screens/trackpads (mousewheel +
Ctrlcommonly zooms) (Firefox bug 1052253).
- The Selection API has been updated so that it has parity with other browsers in terms of how editing hosts are given focus when the selection moves inside them (Firefox bug 1318312). See Behavior of Selection API in terms of editing host focus changes for more details.
SelectionAPI has been updated to match some recent spec changes (Firefox bug 1359371):
offsetparameter is now optional.
nodeparameter is now nullable.
partialContainmentparameter is now optional.
deleteFromDocument()method has been added.
- Also in the
Selection.setPosition()have been added as aliases of
Selection.collapse(), for web compat and WebKit/Blink parity reasons (Firefox bug 1359387).
StorageManager.persisted()methods of the Storage API have been implemented and exposed to
Windowcontexts (Firefox bug 1286717).
- Workers and shared workers can now be created with an identifying
nameproperty. See the
SharedWorker()constructors, and the
SharedWorkerGlobalScopeinterfaces. (Firefox bug 1364297).
setInterval()are now subject to minimum interval throttling for tracking scripts in background tabs — see Throttling of tracking timeout scripts (Firefox bug 1355311).
- Messages sent to service worker contexts (e.g. as the event object of
onmessageare now represented by
MessageEventobjects, for consistency with other web messaging features.
PushManager.subscribe()method now accepts
ArrayBuffers and Base64-encoded strings as
applicationServerKeyvalues (Firefox bug 1337348).
Web Audio API
- A non-standard constructor (which accepted a string enum value indicating the purpose for which the context would be used) for
AudioContextinterface was causing errors to be thrown when the
optionsparameter was provided. We have removed the non-standard constructor. However, please note that the
optionsparameter is not yet supported in Firefox and is currently ignored (Firefox bug 1361475).
getUserMedia()now provides a stereo audio stream by default if the source device provides stereo sound; support to specifically request mono input will come in Firefox 56. This only works on desktop at this time; mobile Firefox does not currently support stereo audio input sources (Firefox bug 971528).
getUserMedia()media capabilities, constraints, and settings
noiseSuppressionnow match the spec; formerly they were
moz-prefixed (Firefox bug 1366415).
- When called with an empty constraints set,
getUserMedia()was incorrectly returning
TypeError. This has been fixed (Firefox bug 1349480).
- The following new WebRTC statistics are available:
firCount(Firefox bug 1348657).
RTCInboundRTPStreamStatsdictionary field formerly called
mozRtthas been renamed to
roundTripTimeto match the specification; in addition, its behavior has been adjusted to match the standard: it contains a double-precision floating point value which estimates the round-trip time based on the RTCP timestamps in the RTCP Receiver Report, measured in seconds (following the algorithm described in RFC 3550, section 6.4.1). (Firefox bug 1344970). However, please be aware that this property is moving to a different dictionary (
RTCRemoteInboundRTPStreamStats) soon (Firefox bug 1380555).
RTCRTPStreamStatsdictionary now includes the fields
nackCount. These return low-level information that can be used to determine how reliable the connection is (Firefox bug 1348657).
RTCOutboundRTPStreamStatsdictionary now includes the field
framesEncoded, which reports the number of frames that have been successfully encoded for the stream; with this information, you can compute the frame rate (Firefox bug 1348657).
- On Android, there's now a pref to turn on hardware video encoding to improve video call performance and save on battery. To be enabled by default in Firefox 56 (Firefox bug 1265755).
Encrypted Media Extensions API
- Firefox currently allows Encrypted Media Extensions to be used in insecure contexts, despite this not being allowed in the specification. This will be changed in the near future, and starting in Firefox 55, deprecation warnings are output to the web console when this is done. (Firefox bug 1361000).
- Firefox currently doesn't require that at least one
MediaKeySystemCapabilitiesobject be included in the
suggestedConfigurationsparameter passed into
Navigator.requestMediaKeySystemAccess(), which the specification does mandate. Starting in Firefox 55, a warning is output to the web console when any audio or video configuration is specified without specifying supported codecs. Soon, failure to include a valid configuration for one or more of audio and video will throw an exception Firefox bug 1368683).
WEBGL_compressed_texture_s3tc_srgbextension is now available to WebGL and WebGL2 contexts (Firefox bug 1325113).
GeolocationAPI is now available only to secure contexts (Firefox bug 1072859).
Storage APIis now available only to secure contexts (Firefox bug 1268804).
- The loading of mixed content is now allowed on localhost (Firefox bug 903966).
- Loading of remote JAR files has been disabled again (Firefox bug 1329336). See Security and the jar protocol for the full story.
- Flash content is now "click-to-activate" (Firefox bug 1317856). This was immediately put into effect for all users of Nightly, and 50% of beta users. For Firefox 55 release version, the plan is to activate this for 5% of users 2 weeks after release, 25% of users 4 weeks after release, and 100% of users 6 weeks after release (Firefox bug 1365714).
- Flash and other plugins can no longer be loaded from any URL scheme except for
https://(Firefox bug 1335475).
- Firefox on Linux can now be made to run in headless mode using the
-headlessflag (see Firefox bug 1356681).
Removals from the web platform
xml:baseattribute can no longer be used to set the base URL for paths appearing in the
styleattribute, for example —
<div xml:base="https://example.com/" style="background:url(picture.jpg)"></div>(Firefox bug 1350521).
scopedattribute has been hidden behind a pref (
layout.css.scoped-style.enabled) in content documents in Firefox 55+, as no other browsers support it.
- Support for the obscure
MSThemeCompatiblevalue of the
http-equivattribute has been removed from Gecko. No other modern browsers support it, and it was causing compatibility problems (Firefox bug 966240).
- The proprietary
:-moz-bound-elementpseudo-class has been removed (Firefox bug 1350147).
- The proprietary
text-decoration-linehas been removed (Firefox bug 1355734).
UIEvent.isCharproperty has never been supported by any browser but Firefox, and it has never been fully-implemented except on macOS. For that reason, it was removed in Firefox 55 to align with other browsers.
- The proprietary Firefox OS Device Storage API has been removed from the platform (Firefox bug 1299500).
aShowDialogparameter of the non-standard
Window.find()method (which could be specified to open up a "Find" dialog in the browser) has been removed (Firefox bug 1348409).
HTMLFormElement.requestAutoComplete()method has been removed (see
HTMLFormElement) (Firefox bug 1270740).
- The non-standard, Mozilla-specific, WebRTC offer options
mozBundleOnlyhave been removed from the
RTCOfferOptionsdictionary and are no longer supported by
RTCPeerConnection.createOffer()(Firefox bug 1196974).
- Support for the proprietary Firefox OS Audio Channels API has been removed from
AudioContext(Firefox bug 1358061).
SVGZoomEventsinterfaces have been removed from the SVG2 spec and Gecko, along with the
onzoom <svg>attribute (Firefox bug 1314388).
Changes for add-on and Mozilla developers
- contextMenus.create()'s command property enables you to open browser action popups, page action popups, and sidebars from the context menu.
- proxy API
- chrome_settings_overrides key enables you to override the browser's homepage.
- browser_style property enables you to have browser-like styling for browser action popups, sidebars, and options pages.
- permissions API
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