A classless stylesheet — ~7 KB gzipped over the wire — that styles semantic HTML as-is and flips themes with one attribute. Change the theme and watch the page re-tint instantly.
No CSS overrides. No JavaScript required. Every component adapts
automatically through CSS custom properties inherited from data-theme.
Built on CSS custom properties from the ground up. No class names, no preprocessors, no config files.
<details> — is styled automatically via element selectors. Write semantic HTML, done.data-theme on <html> and the whole page re-tints. No JS framework needed.data-variant on the element keeps your markup semantic.<main>, <article>, <section> and <form> — coexists safely with any other CSS.--color-primary once and it ripples through the page.njx-ui package ships a full component library — 30+ components, utilities, gradients.~7 KB gzip over the wire (48 KB minified on disk) gets you 9 switchable themes, data-variant accents and safe scoping — features the smaller classless files don't have.
| Feature | Water.css | Simple.css | MVP.css | Pico CSS | njX Classless ✦ |
|---|---|---|---|---|---|
| Size (gzip) | ~3 KB | ~4 KB | ~5 KB | ~10 KB | ~7 KB |
| Built-in themes | 2 (auto) | 2 (auto) | — | 2 + palettes | 9 |
| Runtime theme switch | — | — | — | attribute | 1 attribute |
| Variants (data-variant) | — | — | — | — | ✓ |
| Scoped (safe next to other CSS) | — | — | — | — | ✓ |
| Upgrade path to component library | — | — | — | — | ✓ njX UI |
| Build step required | No | No | No | No | No |
"CSS has everything you need to build a great UI.
You shouldn't have to write it every time — or name a single class."
njX is built on the belief that a CSS library should be invisible — no framework lock-in, no class name memorisation marathons, no config files. Just CSS custom properties doing what they were designed to do.
One line. Any HTML file. Any project. Start in under a minute.