The Digital Press

CSS’s new @function rule, now supported in Chrome 139, allows developers to create custom functions that generate dynamic style values, making CSS more powerful and organized.

Why it matters: Custom CSS functions enable cleaner, reusable, and logic-driven styling, improving design system management and dynamic layouts.

The big picture: This feature is a step toward more complex CSS capabilities like @mixin and @apply for multi-style blocks and greater flexibility.

Quick takeaway: Examples include negation, opacity control, fluid typography, conditional border-radius, responsive sidebars, and extendable light-dark theming.

Commenters say: Users are excited about the cleaner syntax and dynamic capabilities, noting Chrome-only support limits wider adoption for now.