Firefox 152 release notes for developers (Beta)

Changes for web developers

Developer Tools

• The developer tools now have a "Show comments" option to toggle the display of HTML comment nodes in the Inspector. This option can be found in the Settings panel. (Firefox bug 1455294).

APIs

DOM

• The actions read-only property and the maxActions static read-only property of the Notification interface are supported. These contain the notification actions set with ServiceWorkerRegistration.showNotification(), and the platform-dependent maximum number of actions that can be set for a notification, respectively. (Firefox bug 1959931).
• The Element.getAnimations() method can now accept the options.pseudoElement parameter. This allows you to directly target a specific pseudo-element, rather than filtering the results of { subtree: true }. (Firefox bug 1935557).
• The Element.requestPointerLock() method now supports the options.unadjustedMovement parameter. This allows code to disable OS-level mouse acceleration and use raw mouse input instead, which is useful in cases where slow and precise control over mouse movement is needed. (Firefox bug 2037802).

Media, WebRTC, and Web Audio

• The recieveTime property is now included in the metadata returned from RTCEncodedVideoFrame.getMetadata() and RTCEncodedAudioFrame.getMetadata(), and can be passed to the RTCEncodedVideoFrame() and RTCEncodedAudioFrame() constructors as a property in the options parameter. (Firefox bug 2033420).

WebAssembly

• WebAssembly JavaScript Promise Integration (JS-PI) is now available in Nightly builds, where it is enabled by default. This lets WebAssembly code suspend while waiting for JavaScript Promise objects and resume when the promises settle. (Firefox bug 2015877).

Changes for add-on developers

• The ability of extensions to dynamically execute code in their moz-extension: documents with tabs.executeScript, tabs.insertCSS, tabs.removeCSS, scripting.executeScript, scripting.insertCSS, and scripting.removeCSS has been removed. This feature was deprecated in Firefox 149. (Firefox bug 2015559)

  As an alternative, an extension can run code in its documents dynamically by registering a runtime.onMessage listener in the document's script, then sending a message to trigger execution of the required code.

Experimental web features

These features are shipping in Firefox 152 but are disabled by default unless otherwise noted. 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.

• WebAssembly JavaScript Promise Integration (JS-PI): javascript.options.wasm_js_promise_integration

  WebAssembly JavaScript Promise Integration is now available in Nightly builds, where it is enabled by default. (Firefox bug 2015877).

• Check if a media encoding/decoding configuration is supported for WebRTC: media.mediacapabilities.webrtc.enabled

  The webrtc type can now be passed as an option for MediaCapabilities.decodingInfo() and MediaCapabilities.encodingInfo() to check if an encoding/decoding configuration can be used for WebRTC. This replaces the non-standard transmission type, which was previously used as an alias in Firefox. (Firefox bug 1825286).

• TC39 Iterator includes proposal: javascript.options.experimental.iterator_includes

  The Iterator.prototype.includes() method tests whether the iterator will produce a specified value. (Firefox bug 2025779).