Firefox 97 for developers

This article provides information about the changes in Firefox 97 that affect developers. Firefox 97 was released on February 8, 2022.

Changes for web developers


No notable changes


  • The CSS units cap and ic are now supported for use with <length> and <length-percentage> data types. For more information, see Firefox bug 1702924 and Firefox bug 1531223.
  • The CSS property color-adjust has been renamed to print-color-adjust to match the relevant specification. The color-adjust shorthand name is deprecated. See Firefox bug 747595 for details.
  • CSS cascade layers are now available by default. The @layer rule declares a cascade layer, which allows declaration of styles and can be imported via the @import rule using the layer() function. See Firefox bug 1699217 for more details.
  • The global CSS keyword revert-layer has been added to allow rolling back of property values in one cascade layer to the matching rules in the previous cascade layer. This keyword can be applied on any property, including the CSS shorthand property all. For more information, see Firefox bug 1699220.
  • The CSS scrollbar-gutter property is now supported. This gives developers control over reserved space for the scrollbar, preventing unwanted layout changes as the content grows. See Firefox bug 1715112 for more details.


No notable changes


  • The SVG d attribute, used to define a path to be drawn, can now be used as a property in CSS. It accepts the values path() or none. (See Firefox bug 1744599 for details.)




WebDriver conformance (Marionette)

  • Marionette:Quit accepts a new boolean parameter, safeMode, to restart Firefox in safe mode (Firefox bug 1144075).
  • Improved stability for WebDriver:NewSession and WebDriver:NewWindow when waiting for the current or initial document to be loaded (Firefox bug 1739369, Firefox bug 1747359).

Changes for add-on developers

Older versions