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.

Changes for web developers

Developer tools


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:

Page Inspector:



No changes.




No changes.



New APIs


DOM events

Service workers

Media, Web Audio, and WebRTC


  • 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.

WebDriver conformance (Marionette)

  • 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).

Changes for add-on developers

API changes

Manifest changes

No changes.

See also

Older versions