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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

`@function` CSS at-rule

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)

~0.003% 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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