web-feature-id

supports-at-rule

Feature description

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.

Expected release date

Chrome 148, mentioned at I/O

Coding agent assessment

No response

Reference sources

• https://www.bram.us/2026/03/15/at-rule/