This article provides information about the changes in Firefox 55 that will affect developers.
Changes for Web developers
- Added filtering of network requests by column values and other properties (bug 1041895, bug 1354508, bug 1354507) and by using regular expressions (bug 1354495).
- Made it possible to show and hide columns within the Network Monitor (bug 862855).
- Added remote IP (bug 1344523), protocol (bug 1345489), scheme (bug 1356867), cookies and set cookies columns (bug 1356869) to Network Monitor.
SourceMapHTTP header is now supported (prior versions supported the deprecated
X-SourceMapheader, see 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 (bug 1297414). See Differences in markup generation for more details.
dom.forms.datetimeby default on Nightly (bug 1366188).
- Exposed the
transform-boxproperty by default (bug 1208550).
- Implemented the frames() timing function (bug 1248340).
- Implemented the
text-justifyproperty (bug 1343512, bug 276079).
fit-content()unexpectedly reserves space for full clamp size in
clearlogical values —
inline-end— which were previously implemented but preffed off in release channels, are now available in all channels by default (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 (bug 1312328).
- Implemented the proprietary
-moz-context-propertiesproperty (bug 1058040).
- Zero (0) angle value without degree unit is not correctly interpreted in
- 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, bug 1339395).
- Async generator methods are now supported (bug 1353693).
String.prototype.toLocaleUpperCase()methods now support an optional
localeparameter to specify a language tag for locale-specific case mappings (bug 1318403).
Intl.Collatorobject now supports the
caseFirstoption (bug 866473).
- Template call sites objects are now canonicalized per realm, based upon their list of raw strings (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 (bug 1317383).
- The Collaborative Scheduling of Background Tasks API (also known simply 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 (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.
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 (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 bug 1354441, and also see
- Methods of the
DOMTokenListthat modify the list value now automatically trim whitespace and remove duplicate tokens (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 (bug 1368950).
- The event types supported by the
Document.createEvent()method have been updated as per the latest DOM spec (bug 1251198).
MessageEvent.originproperty value is now of type
DOMString, and the
MessageEvent.sourceproperty now takes a
MessageEventSourcevalue (which can be a
ServiceWorkerobject) (bug 1311324).
- The pinch-to-zoom gesture has now been mapped to the
wheelevent plus the + Ctrl key. This mapping was implemented to allow developers to implement simple zooming functionality using the pinch-to-zoom gesture on mobile screens/trackpads (mousewheel + Ctrl commonly zooms) (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 (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 (bug 1359371):
- Also in the
Selection.setPosition()have been added as aliases of
Selection.collapse(), for web compat and WebKit/Blink parity reasons (bug 1359387).
StorageManager.persisted()methods of the Storage API have been implemented and exposed to
Windowcontexts (bug 1286717).
- Workers and shared workers can now be created with an identifying
nameproperty. See the
SharedWorker()constructors, and the
SharedWorkerGlobalScopeinterfaces. (bug 1364297).
setInterval()are now subject to minimum interval throttling for tracking scripts in background tabs — see Throttling of tracking timeout scripts (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. They used to be represented by
ServiceWorkerMessageEventobjects, which have now been deprecated (bug 1311324).
PushManager.subscribe()method now accepts
ArrayBuffers and Base64-encoded strings as
applicationServerKeyvalues (bug 1337348).
- When called with a set of constraints that resulted in there being no media sources available,
getUserMedia()was incorrectly returning
TypeError. This has been fixed (bug 1349480).
WEBGL_compressed_texture_s3tc_srgbextension is now avaiable to WebGL and WebGL2 contexts (bug 1325113).
GeolocationAPI is now available only to secure contexts (bug 1072859).
Storage APIis now available only to secure contexts (bug 1268804).
- The loading of mixed content is now allowed on localhost (bug 903966).
- Loading of remote JAR files has been disabled again (bug 1329336). See Security and the jar protocol for the full story.
- Flash content is now "click-to-activate" (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 (bug 1365714).
- Flash and other plugins can no longer be loaded from any URL scheme except for
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 —
- The proprietary
:-moz-bound-elementpseudo-class has been removed (bug 1350147).
- The proprietary
text-decoration-linehas been removed (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 (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 (bug 1348409).
SVGZoomEventsinterfaces have been removed from the SVG2 spec and Gecko, along with the
onzoom <svg>attribute (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
- Firefox 54 for developers
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