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).

CSS

• CSS features for view transitions in single-page applications (SPAs) are now supported. This provides a way to style the parts of a view transition animation. (Firefox bug 1985809). These include:
  • :active-view-transition pseudo-class
  • view-transition-class property
  • view-transition-name property
  • ::view-transition pseudo-element
  • ::view-transition-group() pseudo-element
  • ::view-transition-image-pair() pseudo-element
  • ::view-transition-new() pseudo-element
  • ::view-transition-old() pseudo-element

APIs

• The lock() and unlock() methods of the ScreenOrientation interface are now supported for Android and for Windows tablets. (Firefox bug 1983483)

• The View Transition API is now supported for SPAs (single-page applications). This provides a mechanism for easily creating animated transitions between different website views. (Firefox bug 1985809).

DOM

• The moveBefore() method is now supported on the Element, DocumentFragment and Document interfaces. This allows moving of an immediate child element of the object, before another of its child elements. Unlike with Node.insertBefore(), moved elements retain their state. (Firefox bug 1983688).

Media, WebRTC, and Web Audio

• Cross-origin <iframe>s now require either user interaction (sticky activation) or explicit permission to redirect the top-level page using window.top.location. See Top navigation in cross-origin frames 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.