Firefox 119 for developers

This article provides information about the changes in Firefox 119 that affect developers. Firefox 119 was released on October 24, 2023.

Changes for web developers






  • The SVG attributes that accept a <length> value now support level 3 <length> CSS data types for all SVG elements. This enables the sizing of SVG elements based on font sizes (cap, rem, etc.), viewport (vh, vw, vmin, etc.), or absolute lengths (px, cm, etc.), e.g. <line x1="10vw" y1="10vh" x2="50vw" y2="50vh"/>. (See Firefox bug 1287054 for more details).


  • The credentialless directive of the Cross-Origin-Embedder-Policy HTTP response header is now supported on desktop platforms (and mobile platforms other than Android), allowing no-cors requests for resources to be made on cross-origin servers that have not explicitly opted into it, albeit without cookies or other credentials (Firefox bug 1851467).



  • ARIA reflection is now supported by default for attributes that do not reference other elements; only non-IDREF attributes are reflected. You can now get and set ARIA attributes on DOM elements directly via JavaScript APIs, rather than by using setAttribute and getAttribute. For example, buttonElement.ariaPressed = "true"; is now supported in addition to buttonElement.setAttribute("aria-pressed", "true"); (Firefox bug 1785412).

WebDriver conformance (WebDriver BiDi, Marionette)


  • When performing a pointerDown action with the middle or right mouse button pressed, the mousedown event as emitted by the related HTML element had the value of the buttons property swapped (Firefox bug 1850086).
  • When performing a scroll action of input type wheel with an origin set to pointer an invalid argument error was inappropriately raised, whereas per the current WebDriver specification this combination is not supported (Firefox bug 1850166).

WebDriver BiDi


  • The list of possible error codes when trying to install a WebExtension by using the Addon:Install command has been updated to match the latest error codes of Firefox (Firefox bug 1852537).

Older versions