Sumi.css - CSS Framework

A closer look at Sumi.css - CSS Framework

What Sumi.css is

Sumi.css is a minimalist, classless-first CSS framework that styles plain, semantic HTML so it looks finished without adding classes by default. The project is stored on GitHub and the repository describes a single CSS file with no JavaScript or dependencies.

What you can actually do with it

Drop the provided sumi.min.css into your project or load it via jsDelivr and your headings, forms, tables, cards, accordions, modals and navigation are styled from the HTML alone. The file is one stylesheet with no build step; use the unminified sumi.css while developing because its comments explain every section.

Sumi has light and dark mode that follows the visitor's system setting automatically, and you can force a mode with data-theme on html or any element. It exposes design tokens as CSS custom properties (all starting with --s-) so you can theme or override colors, fonts, sizes and radii; element styles use :where() with zero specificity so your CSS can override them easily.

Who will find Sumi.css useful

People who prefer writing plain semantic HTML and want a small, dependency-free stylesheet to make pages look finished will appreciate it. Developers who want easy theming via CSS custom properties, automatic light/dark handling, accessible defaults (visible focus rings and ARIA-driven states) and a tiny single-file workflow should find it practical.

Questions people ask about Sumi.css - CSS Framework

How do I add Sumi.css to my site?

Copy sumi.min.css into your project and link it, or load it from the repository through jsDelivr.

Does Sumi.css support dark mode?

Yes - it follows the visitor's system setting automatically and you can force light or dark with data-theme on html or any element.

Will my custom CSS override Sumi's styles?

Yes - element styles are wrapped in :where() so they have zero specificity and your plain selectors will override them without !important.

Sumi.css - CSS Framework was shared on NexURLs by Nexis on October 25, 2026, in Tech & AI.