Web platform features explorer

The @function CSS at-rule defines a custom function that takes CSS values or custom properties as arguments, and returns a CSS value. It can be based on conditional logic such as by using the @media at-rule.

Status

Limited availability

MDN documentation

No MDN documentation found. You can search for the feature on MDN. If you believe that MDN has no documentation about this feature, you can open an issue on MDN's GitHub repository.

Specifications

CSS Functions and Mixins Module (#function-rule), from Cascading Style Sheets (CSS) Working Group (W3C).

Browser support

Chrome 139 Released on 2025-08-05
Chrome Android 139 Released on 2025-08-05
Edge 139 Released on 2025-08-07
Firefox ❌ Vendor position : unknown
Firefox for Android ❌ Vendor position : unknown
Safari ❌ Vendor position : unknown
Safari on iOS ❌ Vendor position : unknown

Surveys

Usage (according to Chrome Platform Status)

~0.002% of page loads. More data at chromestatus.com.

Web Platform Tests (WPT)

View the latest WPT test results for this feature

Developer votes

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