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.
Not yet supported in all major browsers — check the table and provide a fallback.
Browser support
DesktopChrome
1–147Not supported
148+Supportedsince May 5, 2026
Current: 155Edge
12–147Not supported
148+Supportedsince May 7, 2026
Current: 154Firefox
1–156Not supported
157+Supportedsince Sep 29, 2026
Current: 157Safari
✕Not supportedup to 27
Current: 27MobileChrome Android
18–147Not supported
148+Supportedsince May 5, 2026
Current: 155Firefox Android
4–156Not supported
157+Supportedsince Sep 29, 2026
Current: 157Safari iOS
✕Not supportedup to 27
Current: 27How to use
Not supported in Safari, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.
Example
Full syntax and examples are on MDN — see the links below.
Feature detection
There’s no simple runtime check for this feature; rely on the support table and test in your target browsers.