Firefox 60 release notes for developers

Stylo comes to Firefox for Android in 60

Firefox's new parallel CSS engine — also known as Quantum CSS or Stylo — which was first enabled by default in Firefox 57 for desktop, has now been enabled in Firefox for Android.

Changes for web developers

Developer tools

• In the CSS Pane rules view (see Examine and edit CSS), the keyboard shortcuts for precise value increments (increase/decrease by 0.1) have changed from Alt + Up/Down to Ctrl + Up/Down on Linux and Windows, to avoid clashes with default OS-level shortcuts (see Firefox bug 1413314).
• Also in the CSS Pane rules view, CSS variable names will now auto-complete (Firefox bug 1422635). If you enter var( into a property value and then type a dash (-), any variables you have declared in your CSS will then appear in an autocomplete list.
• In Responsive Design Mode, a Reload when… dropdown has been added to allow users to enable/disable automatic page reloads when touch simulation is toggled, or simulated user agent is changed. See Controlling page reload behavior for more details (Firefox bug 1428816).
• The view_source.tab preference has been removed so you can no longer toggle View Source mode between appearing in a new tab or new window. Page sources will always appear in new tabs from now on (Firefox bug 1418403).

HTML

Pressing the Enter key in designMode and contenteditable now inserts <div> elements when the caret is in an inline element or text node which is a child of a block level editing host — instead of inserting <br> elements like it used to. If you want to use the old behavior on your app, you can do it with document.execCommand() (Firefox bug 1430551).

CSS

• The align-content, align-items, align-self, justify-content, and place-content property values have been updated as per the latest CSS Box Alignment Module Level 3 spec (Firefox bug 1430817).
• The paint-order property has been implemented (Firefox bug 1426146).

SVG

No changes.

JavaScript

• ECMAScript 2015 modules have been enabled by default in (Firefox bug 1438139). See ES6 In Depth: Modules and ES modules: A cartoon deep dive for more information, or consult MDN reference docs:

  • <script src="main.js" type="module"> and <script nomodule src="fallback.js">
  • import and export statements.

• The Array.prototype.values() method has been added again (Firefox bug 1420101). Make sure your code doesn't have any custom implementation of this method.

APIs

New APIs

• The Web Authentication API has been enabled in (Firefox bug 1432542).

DOM

• In the Web Authentication API, the MakePublicKeyCredentialOptions dictionary object has been renamed PublicKeyCredentialCreationOptions; this change has been made in Firefox (Firefox bug 1436473).
• The dom.workers.enabled pref has been removed, meaning workers can no longer be disabled since (Firefox bug 1434934).
• The body property is now implemented on the Document interface, rather than the HTMLDocument interface (Firefox bug 1276438).
• PerformanceResourceTiming is now available in workers (Firefox bug 1425458).
• The PerformanceObserver.takeRecords() method has been implemented (Firefox bug 1436692).
• The KeyboardEvent.keyCode attribute of punctuation key becomes non-zero even if the active keyboard layout doesn't produce ASCII characters. See these notes for more detail. Please do not use KeyboardEvent.keyCode in new applications — use KeyboardEvent.key or KeyboardEvent.code instead.
• The Animation.updatePlaybackRate() method has been implemented (Firefox bug 1436659).
• New rules have been included for determining keyCode values of punctuation keys (Firefox bug 1036008).
• The Gecko-only options object storage option of the IDBFactory.open() method has been deprecated (Firefox bug 1442560).
• Promises can now be used within IndexedDB code (Firefox bug 1193394).

DOM events

No changes.

Service workers

No changes.

Media and WebRTC

• When recording or sharing media obtained using getUserMedia(), muting the camera by setting the corresponding track's MediaStreamTrack.enabled property to false now turns off the camera's "in use" indicator light, to help the user more easily see that the camera is not in use (Firefox bug 1299515). See User privacy for more details. See also this blog post.
• Removing a track from an RTCPeerConnection using removeTrack() no longer removes the track's RTCRtpSender from the peer connection's list of senders as reported by getSenders() (Firefox bug 1290949).
• The RTCRtpContributingSource and RTCRtpSynchronizationSource objects' timestamps were previously being reported based on values returned by Date.getTime(). In Firefox 60, these have been fixed to correctly use the Performance Timing API instead (Firefox bug 1433576).
• As per spec, the ConvolverNode() constructor now throws a NotSupportedError DOMException if the referenced AudioBuffer does not have 1, 2, or 4 channels (Firefox bug 1443228).
• The obsolete RTCPeerConnection event handler RTCPeerConnection.onremovestream has been removed; by now you should be using removetrack events instead (Firefox bug 1442385).
• The primary name for RTCDataChannel is now in fact RTCDataChannel, instead of being an alias for DataChannel. The name DataChannel is no longer supported (Firefox bug 1173851).

Canvas and WebGL

• If the privacy.resistFingerprinting preference is set to true, the WEBGL_debug_renderer_info WebGL extension will be disabled from now on (Firefox bug 1337157).

CSSOM

No changes.

HTTP

• SameSite cookies are now supported (Firefox bug 795346). See Set-Cookie for more information.

Security

The X-Content-Type-Options header, when set to no-sniff, now follows the specification for JavaScript MIME types. In particular, text/json and application/json are no longer valid values (Firefox bug 1431095).

Plugins

No changes.

Other

Fetches that include credentials can now share connections with fetches that don't include credentials. For example, if the same origin requests some web fonts as well as some credentialed user data from the same CDN, both could share a connection, potentially leading to a quicker turnaround (Firefox bug 1363284).

Removals from the web platform

HTML

No changes.

CSS

• The proprietary -moz-user-input property's enabled and disabled values are no longer available (Firefox bug 1405087).
• The proprietary -moz-border-top-colors, -moz-border-right-colors, -moz-border-bottom-colors, and -moz-border-left-colors properties have been removed from the platform completely (Firefox bug 1429723).

JavaScript

The non-standard expression closure syntax has been removed (Firefox bug 1426519).

APIs

No changes.

SVG

No changes.

Other

No changes.

Changes for add-on and Mozilla developers

WebExtensions

Theme API:

• headerURL is now optional
• When creating a browser theme, any text-shadow applied to the header text is removed if no headerURL is specified (see Firefox bug 1404688).
• New properties are supported:
  • tab_line
  • tab_selected
  • popup
  • popup_border
  • popup_text
  • tab_loading
  • icons
  • icons_attention
  • frame_inactive
  • button_background_active
  • button_background_hover