Firefox 145 release notes for developers (Beta)

Changes for web developers

CSS

• The text-autospace property is now supported, allowing automatic spacing adjustments between characters from different scripts (Firefox bug 1981086, Firefox bug 1869577).

• Firefox now supports the legacy -webkit-fill-available keyword as a value for the CSS width and height properties, to improve web compatibility. This keyword is an alias for the recently-standardized stretch keyword (i.e., width: stretch and height: stretch) which isn't yet supported in Firefox. (Firefox bug 1988938, Firefox bug 1789477).

JavaScript

• Firefox now supports the Atomics.waitAsync() static method, which allows synchronization of threads based upon the value in a shared memory location. The method waits asynchronously on the value and returns an object representing the result of the operation. It is non-blocking and usable on the main thread. (Firefox bug 1884148).

HTTP

• The Integrity-Policy and Integrity-Policy-Report-Only HTTP headers are now supported for script resources. These allow websites to enforce subresource integrity guarantees for scripts. Note that the endpoints key is not yet supported (violations are logged to console). (Firefox bug 1984973).

APIs

Media, WebRTC, and Web Audio

• RTCEncodedVideoFrame and RTCEncodedAudioFrame are now serializable objects, and RTCEncodedAudioFrame() and RTCEncodedVideoFrame() copy constructors are supported. These changes allow frames to be cloned, and to be shared between workers and the main thread. (Firefox bug 1868223 and Firefox bug 1975032).

Changes for add-on developers

• Cookies created with cookies.set() are now validated, and invalid cookies are rejected. This change was implemented in Nightly only from Firefox 142. (Firefox bug 1976509)

Experimental web features

These features are shipping in Firefox 145 but are disabled by default. To experiment with them, search for the appropriate preference on the about:config page and set it to true. You can find more such features on the Experimental features page.