UnoCSS
On-demand atomic CSS engine with swappable presets, ~6kb, no core utilities
UnoCSS is an atomic CSS engine by Anthony Fu that generates utilities on demand with no parsing, AST or file scanning. It ships no core utilities at all — everything comes from presets, so preset-wind3 and preset-wind4 reproduce Tailwind v3 and v4 syntax while preset-icons turns any Iconify icon into a pure-CSS class and preset-attributify moves utilities into HTML attributes. Integrations exist for Vite, Webpack, PostCSS, Nuxt, Astro, Svelte, Next.js and a CDN runtime, plus VS Code, JetBrains and Zed extensions. It is for teams that want Tailwind-shaped ergonomics with their own rule set and faster builds.
npm install -D unocssReach for UnoCSS over Tailwind when the project needs custom utility rules, attributify markup, or pure-CSS Iconify icons without a component wrapper — preset-icons alone (i-lucide-check as a class) removes a whole icon dependency. Pin the preset explicitly: preset-wind3 is Tailwind v3 syntax and preset-wind4 is v4, and copy-pasted Tailwind snippets silently miss utilities under the wrong one. Do not assume Tailwind plugins or shadcn/ui registries work here; most shadcn components assume real Tailwind and need the wind preset plus manual checking.
Why it is here. The strongest non-Tailwind atomic CSS engine, and the only one where the utility vocabulary itself is a swappable, authorable input.
- no core utilities — presets only
- preset-icons: any Iconify icon as pure CSS
- attributify and tagify modes
- ~6kb min+brotli, zero deps
- v66.x, MIT, 18.9k stars
Verified 2026-08-15. HTTP 200. https://unocss.dev/, https://unocss.dev/presets/ (full official preset list), https://github.com/unocss/unocss
