CSS custom properties (often called CSS variables) declare a value on a selector — usually `:root` — and reference it via `var(--name)`. They are the modern bridge between design tokens and runtime CSS: a single source of truth that themes and components both read. Most catalogued sites with rigorous design systems (Linear, Vercel, Stripe) expose dozens to hundreds of custom properties; AI2 Design's CSS export format mirrors this convention.
Glossary · design tokens
CSS Custom Properties
User-defined CSS variables (e.g. `--color-accent`) scoped to a selector and inherited by descendants.
Also known as
- CSS variables
External reference
MDN — Custom PropertiesCatalogued examples
2 catalogued sites demonstrate css custom properties in production.