Sass vs Less: Which CSS Preprocessor?
Sass is the dominant, feature-rich CSS preprocessor; Less is a lighter JavaScript-based preprocessor with a smaller modern footprint.
Sass (via the Dart implementation) leads CSS preprocessing with mature modules, functions, mixins, and the widest ecosystem and tooling support. Less offers similar variables, mixins, and nesting with a JavaScript implementation, historically tied to older Bootstrap, but has lost momentum as Sass and native CSS advanced. Sass wins on features, ecosystem, and active development; Less wins for legacy projects already built on it.
| Sass | Less | |
|---|---|---|
| Implementation | Dart Sass (active) | JavaScript |
| Features | Rich (modules, functions) | Solid, fewer |
| Ecosystem | Largest, active | Smaller, legacy-leaning |
| Adoption | Industry standard | Declining |
| Best for | New and large projects | Existing Less codebases |
Use case and ecosystem
Sass suits new and large projects wanting the richest feature set, mature modules, and the broadest tooling and community support. Less mainly suits existing codebases and older framework integrations already invested in it; new projects rarely choose Less today.
Build and CI
Both compile to CSS as a build step. Either compiles on managed runners, where faster runners shorten preprocessor compilation within the frontend build.
The verdict
Starting fresh or scaling a large stylesheet: Sass, the modern standard. Maintaining an existing Less codebase: keep Less unless a migration is worth it. For new work, Sass is the clear default.