New features in Firefox 157 (released on 2026-09-29)

• at-rule()

  Limited availability

  The at-rule() function, when used with @supports, checks if a CSS at-rule is supported. For example @supports at-rule(@starting-style) checks if the @starting-style at-rule is supported.

  Learn more

  • Chrome 148 Released on 2026-05-05
  • Chrome Android 148 Released on 2026-05-05
  • Edge 148 Released on 2026-05-07
  • Firefox 157 Released on 2026-09-29
  • Firefox for Android 157 Released on 2026-09-29
  • Safari Not supported Position: support
  • Safari on iOS Not supported Position: support

  Baseline availability blocked since September 2026 by Safari (1 months)