This article provides information about the changes in Firefox 62 that will affect developers. Firefox 62 was released on September 5, 2018.

Changes for web developers

Developer tools

• The Shape Path Editor is now available by default — seeEdit Shape Paths in CSS for more information.

• You can now split the Rules view out into its own pane, separate from the other tabs on the CSS pane. SeePage inspector 3-pane mode for more details.

• The Grid inspector has updated features, and all new documentation — seeCSS Grid Inspector: Examine grid layouts.

• You now have four options for the location of the Developer Tools. In addition to the default location on the bottom of the window, you can choose to locate the tools on either the left or right sides of the main window or in a separate window (Firefox bug 1192642).

• A close button has been added to thesplit console toolbar.

• If the option to "Select an iframe as the currently targeted document" is checked, the icon will appear in the toolbar while the Settings tab is displayed, even if the current page doesn't include any iframes (Firefox bug 1456069).

• TheNetwork Monitor'sCookies tab now shows the cookiesamesite attribute (Firefox bug 1452715).

• Responsive design mode now works inside container tabs (Firefox bug 1306975).

• WhenCORS errors occur and are reported on the console, Firefox now provides a link to the corresponding page in ourCORS error documentation (Firefox bug 1475391).

• Create a screenshot of the current page (with an optional filename) from the Console tab (Firefox bug 1464461) using the following command:

  bash

  :screenshot <filename.png> --fullpage

  where<filename.png> is the desired filename. The file will be saved to your downloads folder. The--fullpage parameter is optional, but if included, it will save the full web page. This option also adds-fullpage to the name of the file. For a list of all options available for this command, enter::screenshot --help

Removals

• TheDeveloper Toolbar/GCLI (accessed withShift +F2),has been removed from Firefox (Firefox bug 1461970). Both the Developer Toolbar UI and the GCLI upstream library have become unmaintained, some of its features are broken (some ever since e10s), it is blocking theunsafeSetInnerHTML work, usage numbers are very low, alternatives exist for the most used commands.

HTML

No changes.

CSS

• :-moz-selection has been unprefixed to::selection (Firefox bug 509958).
• x is now supported as a unit for the<resolution> type (Firefox bug 1460655).
• shape-margin,shape-outside, andshape-image-threshold are now enabled by default (Firefox bug 1457297).

Removals

• All XULdisplay values with the exception of-moz-box and-moz-inline-box have been removed from non-XUL documents inFirefox bug 1288572.

SVG

No changes.

JavaScript

• TheWebAssembly.Global() constructor is now supported, along with global variables in WebAssembly (Firefox bug 1464656).
• TheArray.prototype.flat() andArray.prototype.flatMap() methods are now enabled by default (Firefox bug 1435813).
• Theimport.meta property has been implemented to expose context-specific metadata to a JavaScript module (Firefox bug 1427610).
• JavaScriptstring literals may now directly contain the U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR characters. As a consequence,JSON syntax is now a subset of JavaScript literal syntax (seeFirefox bug 1435828 and the TC39 proposaljson-superset).
• For out-of-boundstyped array indexes,Reflect.defineProperty() andReflect.set() will now returnfalse instead oftrue (Firefox bug 1308735).

Removals

• TheDOMPoint andDOMPointReadOnly constructors no longer support an input parameter of typeDOMPointInit; the values of the properties must be specified using thex,y,z, andw parameters (Firefox bug 1186265).
• TheURL.createObjectURL() method no longer supports creating object URLs to represent aMediaStream. This capability has been obsolete for some time, since you can now setHTMLMediaElement.srcObject to theMediaStream directly (Firefox bug 1454889).

APIs

New APIs

• TheSpeech Synthesis API (Text-to-Speech) is now enabled by default on Firefox for Android (Firefox bug 1463496).

DOM

• TheDOMPointReadOnly interface now supports the static functionDOMPointReadOnly.fromPoint(), which creates a new point object from a dictionary that's compatible withDOMPointInit, which includes anyDOMPoint object. This function is also available onDOMPoint (Firefox bug 1186265).
• For compatibility purposes, theEvent.srcElement property is now supported. It is an alias forEvent.target (Firefox bug 453968).
• Navigator.registerProtocolHandler() now must only be called from a secure context (Firefox bug 1460506).
• TheNavigator.registerContentHandler() method has been disabled by default in preparation for being removed entirely, as it's been obsolete for some time (Firefox bug 1460481).
• TheDataTransfer() constructor has been implemented (Firefox bug 1351193).
• Document.domain can no longer returnnull (Firefox bug 819475). If the domain cannot be identified, thendomain returns an empty string instead ofnull.
• Added theconsole.timeLog() method to display the current value of a console timer while continuing to track the time (Firefox bug 1458466).
• Addedconsole.countReset() to reset a console counter value (Firefox bug 1459279).

DOM events

No changes.

Service workers

No changes.

Media, Web Audio, and WebRTC

• The"media.autoplay.enabled" preference now controls automatic playback of both audio and video media, instead of just video media (Firefox bug 1413098).
• TheChannelSplitterNode has been fixed to correctly default to having 6 channels with thechannelInterpretation set to"discrete" and thechannelCountMode set to"explicit", as per the specification (Firefox bug 1456265).

Removals

• Theuserproximity anddeviceproximity events, as well as theUserProximityEvent andDeviceProximityEvent interfaces, have been disabled by default behind thedevice.sensors.proximity.enabled preference (Firefox bug 1462308).
• Thedevicelight event of typeDeviceLightEvent has been disabled by default behind thedevice.sensors.ambientLight.enabled preference (Firefox bug 1462308).
• TheDOMSubtreeModified andDOMAttrModifiedmutation events are no longer thrown when thestyle attribute is changed via the CSSOM (Firefox bug 1460295.
• Support forCSSStyleDeclaration.getPropertyCSSValue() has been removed (Firefox bug 1408301).
• Support forCSSValue,CSSPrimitiveValue, andCSSValueList has been removed (Firefox bug 1459871).
• window.getComputedStyle() no longer returnsnull when called on aWindow which has no presentation (Firefox bug 1467722).

HTTP

Removals

• The deprecated CSPreferrer directive has been removed. Please use theReferrer-Policy header instead (Firefox bug 1302449).

Security

No changes.

Plugins

No changes.

WebDriver conformance (Marionette)

New features

• CommandWebDriver:ElementSendKeys has been made WebDriver conforming for file uploads (Firefox bug 1448792).
• User prompts as raised bybeforeunload events are automatically dismissed forWebDriver:Get,WebDriver:Back,WebDriver:Forward,WebDriver:Refresh, andWebDriver:Close commands (Firefox bug 1434872).
• WebDriver:PerformActions forCtrl +Click synthesizes acontextmenu event (Firefox bug 1421323).

API changes

• Removed obsolete endpoints includinggetWindowPosition,setWindowPosition,getWindowSize, andsetWindowSize (Firefox bug 1348145).
• WebDriver commands which return success with datanull now return an empty dictionary (Firefox bug 1461463).

Bug fixes

• WebDriver:ExecuteScript caused cyclic reference error forWebElement collections (Firefox bug 1447977).
• Dispatching apointerMove orpause action primitive could cause a hang, and the command to never send a reply (Firefox bug 1467743,Firefox bug 1447449).

Other

No changes.

Changes for add-on developers

API changes

• Added thewebRequest.getSecurityInfo() API to examine details of TLS connections (Firefox bug 1322748).
• Added thebrowserSettings.newTabPosition to customize where new tabs open (Firefox bug 1344749).
• windowTypes has been deprecated inwindows.get(),windows.getCurrent(), andwindows.getLastFocused() (Firefox bug 1419132).
• It's now possible to modify a browser action on a per-window basis (Firefox bug 1419893).

Manifest changes

• Newopen_at_install property of thesidebar_action manifest key enables extensions to control whether their sidebars should open automatically on install or not (Firefox bug 1460910).
• Changes to thebrowser_style property of various manifest keys:
  • Inpage_action andbrowser_action it defaults tofalse.
  • Insidebar_action andoptions_ui it defaults totrue.

Theme changes

• Newtab_background_separator property of thetheme manifest key enables extensions to change the color of the tab separator (Firefox bug 1459455).

Removals

• Support for unpacked sideloaded extensions has been removed (Firefox bug 1385057).
• The warning aboutbrowser_style displayed when temporarily loading an extension for testing is no longer displayed (Firefox bug 1404724).