Firefox 155 release notes for developers (Beta)

Changes for web developers

APIs

DOM

• The SVGAElement interface now implements the HyperlinkElementUtils mixin. As a result, SVG <a> elements expose the same URL component properties as HTML <a> elements: protocol, username, password, host, hostname, port, pathname, search, and hash. The read-only origin property is also exposed. (Firefox bug 2058578).
• The SVGNumberList, SVGPointList, SVGStringList, and SVGTransformList interfaces now support indexed setters. This means you can replace an item in the list using bracket notation, such as transformList[0] = newTransform, instead of calling replaceItem(). The SVGLengthList interface already supports indexed setters. (Firefox bug 2059426).

Media, WebRTC, and Web Audio

• The error event fired on an RTCDataChannel object may now report sctp-failure in its error.errorDetail property if the transport is closed due to an error. In addition, RTCError and RTCErrorEvent are now available in dedicated workers (this exposure is not yet in the specification). (Firefox bug 1814460).

WebAssembly

• The Wide arithmetic proposal has been implemented, which allows 128-bit integer additions, multiplications, and subtractions to be represented in Wasm. (Firefox bug 2062374).

WebDriver conformance (WebDriver BiDi, Marionette)

General

• Disabled the download panel to prevent the current document from losing focus when a download begins. (Firefox bug 2035439).
• Fixed the Actions API so that the dblclick event is fired when performing a double-click while holding down the Ctrl key on non-macOS platforms. (Firefox bug 2058556).

WebDriver BiDi

• Updated the Mozilla-specific moz:debugging module to no longer rely on the same nested event loop API as DevTools, which prevents conflicts when WebDriver BiDi and DevTools are used in parallel. (Firefox bug 2041335).
• Fixed the browsingContext.reload command failing when used for frames. (Firefox bug 2030909).
• Removed support for the contexts argument in the session.unsubscribe command. From now on, clients can unsubscribe only by event name or subscription ID. (Firefox bug 1988723).

Changes for add-on developers

Experimental web features

These features are shipping in Firefox 155 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.