Firefox 92 for developers

This article provides information about the changes in Firefox 92 that will affect developers. Firefox 92 was released on September 7, 2021.

Note: See also Time for a review of Firefox 92 on Mozilla Hacks.

Changes for web developers


No changes




  • Firefox will automatically upgrade an HTTP request to HTTPS when a usable HTTPS RR is available. It will also use information provided in an HTTPS RR to optimize the process of establishing HTTPS connections⁠—this is conceptually similar to using the Alt-Svc header. (Firefox bug 1721132).


  • The disabledFeatures static property has been implemented for Custom Elements (Firefox bug 1723396).


Media, WebRTC, and Web Audio

WebDriver conformance (Marionette)

  • Improved support for the webSocketUrl capability, which now returns the WebDriver BiDi websocket URL if true was passed and if BiDi is supported. (Firefox bug 1692984).

Changes for add-on developers

Older versions