Firefox 144 for developers

Changes for web developers

MathML

Removals

• Support for the deprecated MathML STIXGeneral font has now been removed. The setting mathml.stixgeneral_operator_stretching.disabled has also been removed. (Firefox bug 1336058).

APIs

Media, WebRTC, and Web Audio

• Framebusting Intervention: Cross-origin <iframe>s require either user interaction or explicit permission in order to redirect the top level page using window.top.location, aligning behavior with Chrome and Safari. See Window.top navigation for more information. (Firefox bug 1419501).
• RTCDataChannel instances are now transferrable objects, and hence can be passed to workers. (Firefox bug 1209163).
• The closing event and the onclosing() event handler are now supported on the RTCDataChannel interface. (Firefox bug 1611953).
• The getUserMedia() and getDisplayMedia() methods of the MediaDevices interface now support the resizeMode constraint. This constraint allows developers to request video that matches other constraints, such as resolution and frame rate, even if the requested constraints are not supported by the underlying hardware. The browser may then crop, downscale, or reduce the frame rate of the video captured from a camera, or downscale (but not crop) the video captured from a screen or window. (Firefox bug 1286945).

Changes for add-on developers

• Adds the ability to determine the priority of CSS injected from the "content_scripts" manifest key, in scripting.registerContentScripts() with the cssOrigin property on scripting.RegisteredContentScript, and the cssOrigin property in contentScripts.register. By default, the "author" origin takes precedence. (Firefox bug 1679997)

Experimental web features

These features are shipping in Firefox 144 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.