Firefox 72 for Developers

This article provides information about the changes in Firefox 72 that will affect developers. Firefox 72 was released on January 7, 2020.

Console:

• In the multi-line mode of the interactive JS interpreter, you can open and save files using the keyboard shortcuts Ctrl + O and Ctrl + S, respectively (bug 1592308).
• You can set a preference so that asynchronous messages are visually separated (bug 1592969).

JavaScript debugger:

• You can now right/Ctrl click on objects in the Scopes panel, and choose Property set or Property get to set watchpoints (bug 1574192).

Network Monitor:

• The Timings tab now shows queued, started, and downloaded times for each resource (bug 1580431).

Page Inspector:

• You can set a preference to enable a simulator for different values of the prefers-color-scheme media feature (bug 1550804).

Removals

• The Scratchpad feature has been removed (bug 1519103).

No changes.

• CSS Shadow Parts are now enabled. This includes the part attribute and ::part pseudo-element, which allow shadow hosts to selectively expose chosen elements from their shadow tree to the outside page for styling purposes (bug 1559074).
• CSS Motion Path has been shipped (bug 1582554, also see the Intent to Ship). This includes:
  • offset
  • offset-path
  • offset-anchor
  • offset-distance
  • offset-rotate
• The individual transform properties — scale, rotate, and translate — are now enabled by default (bug 1424900).

Removals

No changes

• The nullish coalescing operator has been implemented (bug 1566141).

New APIs

• FormDataEvent and event-based form participation is now enabled by default (bug 1594708).

DOM

• The Geolocation API has had some interface name updates, as per recent spec changes (bug 1575144):
  • Coordinates has been changed to GeolocationCoordinates.
  • Position has been changed to GeolocationPosition.
  • PositionError has been changed to GeolocationPositionError.
• A number of properties have been updated to use standard stringifiers (bug 824857):
  • DOMTokenList.value
  • HTMLAnchorElement.href
  • Location.href
  • MediaList.mediaText
  • URL.href
  • WorkerLocation.href

DOM events

• Notification.requestPermission() and PushManager.subscribe() can now only be called in response to a user gesture such as a click event (bug 1593644).

Service workers

• The crossOriginIsolated property is now supported (bug 1591892).

Media, Web Audio, and WebRTC

• The MediaDevices.getDisplayMedia() method can now only be called in response to a user gesture such as a click event (bug 1580944).
• The RTCRtpContributingSource dictionary can now include the rtpTimestamp property, which is a source-generated time at which the packet's media was generated or sampled (bug 1583867).

Removals

• Removed the non-standard window.mozPaintCount property. (bug 1591968)
• The BatteryManager interface is no longer exposed to web content (bug 1441976).
• Navigator.vibrate() is no longer supported in cross-origin <iframe>s (bug 1591113).
• WebRTC no longer supports the rid= and pt= parameters on the simulcast attribute. The new syntax for a line such as "a=simulcast: send rid=7 recv rid=8" is now "a=simulcast: send 7 recv 8". The new syntax has been supported since Firefox 68, so now it's time tor retire support for the old syntax (bug 1470568).

• Opting-out of MIME sniffing using X-Content-Type-Options is now also applied to top-level documents if a Content-type is provided. This can cause HTML web pages to be downloaded instead of being rendered when they are served with a MIME type other than text/html. Make sure to set both headers correctly. (bug 1591932).
• Dropped the support for HTTP Public Key Pinning (HPKP) because of the low adoption rate and interoperability risk. The Public-Key-Pins and Public-Key-Pins-Report-Only headers are now silently ignored bug 1412438.

No changes.

• Removed Anon and AnonAttribute strategies from WebDriver:FindElement and WebDriver:FindElements commands (bug 1587627).
• Webdriver:TakeScreenshot no longer fails if captured area exceeds upper maximum bound for the canvas width, height, or size (bug 1590064).

• The browserSettings.ftpProtocolEnabled property has been implemented (bug 1592687).
• The BrowserSetting.onChange event has been implemented (bug 1410412).
• The captivePortal.canonicalURL property has been implemented (bug 1592932).
• The callback functions for the browserAction.onClicked and pageAction.onClicked events now include a OnClickData property containing an object whose properties describe the mouse button pressed along with any keyboard modifiers (bug 1405031). This allows support for additional types of mouse click.

No changes.

• Hacks release post: Firefox 72 — our first song of 2020