UnoCSS

UnoCSS is an atomic CSS engine that generates styles on demand. It has no built-in utilities; you add them through presets, which keeps the core small.

UnoCSS generates CSS for the classes your project uses, so the output stays small and matches what you write. Shortcuts let you group utilities under names you can reuse. Presets add features such as attributify mode, pure CSS icons and a variant group transformer. The engine integrates with Vite, Webpack, PostCSS and the command line, and an inspector helps you debug the styles it generates. A CDN runtime build is also available for quick prototypes.

• On-demand atomic CSS generation
• Shortcuts for reusable utility groups
• Presets for icons, attributify and more
• Integrations with Vite, Webpack and PostCSS
• Inspector for debugging generated styles

Developers who want Tailwind-style utility classes with a custom set of rules. Teams that prefer to build their own utility set through presets, and build tool users who want a flexible engine, will find it a good fit.

UnoCSS is released under the MIT license, according to its page, so it is free to use. The core has no default utilities, so you need to add a preset to get the familiar class set. Check the presets page to see which ones match your project before you start.