How to css variables vs sass vs less for typography tokens
- Step 1Native CSS variables — :root { --font-size-base: 1rem; }. Inheritable, mutable, scoped to DOM tree. Runtime cost: var() resolution per use (negligible). Theming via media queries or [data-theme] attributes.
- Step 2Sass variables — $font-size-base: 1rem;. Compile-time substitution — no runtime cost. Theming requires recompiling Sass with different variable values. Less flexible but slightly faster.
- Step 3Pick the modern default — Native CSS variables for any new project. Sass for projects already using it where migration cost outweighs benefits. Less for legacy maintenance only.
Frequently asked questions
Is there a runtime performance difference?+
Negligible in practice. Modern browsers resolve var() in microseconds. Concerns about CSS variable performance dominated 2017 conversation; benchmarks in 2026 show no meaningful difference.
Can I migrate from Sass to native gradually?+
Yes — emit both Sass variables and native CSS variables from the same token source. Components migrate one at a time; both styles coexist during transition.
Why are CSS variables better for theming?+
Runtime mutation. [data-theme="dark"] :root { --bg-color: black; } switches instantly via DOM attribute. Sass variables compile away; theming requires multiple compiled CSS files.
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