Sumi.css
A classless CSS framework that styles plain HTML
Developer ToolsFreeOpen source · verified#css#frontend#framework
Listed by the ProductPerch team from Hacker News · not launched here yet
What is Sumi.css?
Sumi.css is a minimalist CSS framework designed for writing plain, semantic HTML. It applies styling directly to standard HTML elements, so pages look complete without adding extra classes. The entire library is contained in a single file with no build step, no JavaScript, and no external dependencies.
The framework weighs 6.7 KB when minified and gzipped. It includes built-in styles for headings, paragraphs, lists, navigation bars, buttons, form fields, tables, cards, accordions, and modals. Users can add custom classes only when they need specific overrides. Element styles use zero specificity, meaning custom CSS always takes precedence without requiring !important rules.
Sumi.css supports automatic light and dark modes based on system settings, with an optional data-theme attribute to force a preference. Every color, font, size, and border radius is controlled through CSS custom properties for easy theming. The code includes visible focus rings, ARIA-driven states, and reduced motion support to meet accessibility standards. It is released under the MIT license.
Sumi.css features
- Styles plain HTML elements automatically without extra classes
- Single file distribution with no build step or dependencies
- Automatic light and dark mode following system preferences
- Fully customizable colors and spacing using CSS variables
- Zero specificity element styles for predictable CSS overrides
- Built-in accessible components like modals, accordions, and forms
- Includes a tutorial and cheat sheet for quick reference
Who uses Sumi.css and for what
- Building simple landing pages with minimal markup and fast load times
- Prototyping internal dashboards where rapid HTML styling is needed
- Creating static documentation sites that require clean typography and tables
- Developing lightweight web apps that avoid heavy frontend frameworks
- Adding consistent form styling and button designs across legacy projects
Sumi.css FAQ
Is Sumi.css free?
Yes, Sumi.css is available under the MIT license and can be used freely for personal or commercial projects.
Does Sumi.css require a build step?
No, the framework consists of a single CSS file that can be linked directly in your HTML without any bundlers or compilers.
What browsers does Sumi.css support?
The website does not specify exact browser compatibility requirements.
Can I customize the default colors and fonts?
Yes, every visual property is defined as a CSS custom property, allowing you to override them easily without !important rules.
Is Sumi.css open source?
Yes, the source code is publicly hosted on GitHub under the vladocar/Sumi.css repository.
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