Firefox 109 for developers

This article provides information about the changes in Firefox 109 that will affect developers. Firefox 109 was released on January 17, 2023.

Changes for web developers


  • The range element supports the list attribute, which links via an id to a <datalist> to allow Firefox to display tick marks along the range.



No notable changes.



  • SVGGraphicsElement.getTransformToElement() has been removed. This follows its removal from the SVG2 specification in 2015, and from other major browsers. (Firefox bug 1803790).
  • The SVGGraphicsElement.nearestViewportElement and SVGGraphicsElement.farthestViewportElement attributes have been disabled by default in nightly and early beta builds (behind preference svg.nearestAndFarthestViewportElement.enabled). SVGElement.viewportElement can be used as an alternative to SVGGraphicsElement.nearestViewportElement. They have been removed from the SVG2 specification and are likely to be removed entirely from Firefox in a future release. (Firefox bug 1133174).




WebDriver conformance (WebDriver BiDi, Marionette)

WebDriver BiDi

  • The connection details for WebDriver BiDi are now written to WebDriverBiDiServer.json instead of WebDriverBiDiActivePort, which contains both the port (ws_port) and the host (ws_host). This file is located in the Firefox profile folder (Firefox bug 1792875).
  • Added support for subscribing / unsubscribing to individual contexts when using session.subscribe and session.unsubscribe (Firefox bug 1723102).
  • Added support for serializing Node objects (Firefox bug 1770731).
  • Fixed the columnNumber for exceptions and stackTraces to be 0-based (Firefox bug 1796073).


  • Fixed a bug where WebDriver:NewWindow and WebDriver:SwitchToWindow were not focusing the new window properly (Firefox bug 1798655).
  • Fixed a bug where WebDriver:FindElement (and similar commands) would fail if the Firefox window was occluded by other applications on Windows (Firefox bug 1802473).

Changes for add-on developers

Older versions