# master-co/css

The markup-driven CSS language and framework — readable by humans, reliable for agents.

Repository: https://github.com/master-co/css
Canonical: https://ross.abutalabs.com/products/master-co-css
Homepage: https://css.master.co
Language: TypeScript
License: MIT
License Family: permissive
Topics: css, html, responsive, engine, language, master, progressive-rendering, runtime, server-side-rendering, zero-runtime, runtime-rendering, markup-driven, dynamic-class, framework
Last push: 2026-08-01T15:25:01+00:00

## Health v2 (maintenance only)
Score: 84/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 95, release rhythm 60, longevity 100
- inputs: {"age_days": 1734, "days_push": 32, "days_rel": 40, "gap_med": 1.0, "n_releases_24m": 43}
- flags: prerelease_only
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1945, forks 44 (observed 2026-08-28T04:05:57.746134+00:00)

## What it is
Master CSS is a virtual CSS language and framework that lets developers style HTML entirely through enhanced class-name syntax, with a runtime engine that observes the DOM and generates real CSS rules automatically. It supports responsive breakpoints, states, selectors, color schemes, and hybrid server-side rendering in roughly 14KB, with framework-agnostic setup and a VS Code language service.

## Use cases
- style web UIs without writing separate CSS files
- build a design system using only HTML class names
- add responsive styles with breakpoint variants in markup
- pre-generate CSS on the server for SSR apps like Next.js
- quickly prototype pages via a CDN script tag
- replace utility-first frameworks like Tailwind with a new CSS syntax
- get syntax highlighting and autocomplete for class names in VS Code

## When to choose
- you want utility-first styling with a more structured, near-native CSS syntax
- you need zero-config setup that works via CDN or any framework (React, Vue, Angular, Svelte, Laravel)
- you want runtime JIT styling plus server-side pre-generation (hybrid rendering)
- you need broad browser support including IE 11 via Mutation Observer

## When to avoid
- your team prefers traditional semantic CSS classes and stylesheets
- you rely on an ecosystem of plugins built for Tailwind CSS
- you dislike learning a custom class-name syntax for styling
- you need a full component library rather than a styling engine

## Facets
- artifact type: framework
- maturity: active
- function: css-framework, frontend-framework, ui-components, ssr, theme
- domain: web-development, frontend, web-design
- platform: browser, cross-platform
- tags: virtual-css, utility-first, atomic-css, jit, zero-runtime, markup-driven, responsive-design, vscode-extension, cdn, nodejs, web-server

## Member repositories
- master-co/css (main) score 84

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:57.746134+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:07:58.132798+00:00, confidence not recorded.
  - readme: https://github.com/master-co/css (fetched 2026-08-28T04:05:57.746134+00:00, sha 4964723ffbbc)
  - homepage: https://css.master.co (fetched 2026-08-29T10:47:26.697509+00:00, sha 14f2d2122972)
  - site_page: https://css.master.co/docs/why-master-css (fetched 2026-08-29T10:47:26.718093+00:00, sha 1c4a49dcd7d9)
  - site_page: https://css.master.co/docs/setup (fetched 2026-08-29T10:47:26.720900+00:00, sha e8263af6436c)
  - site_page: https://css.master.co/docs/selectors (fetched 2026-08-29T10:47:26.722802+00:00, sha f43b2601b8a0)
  - site_page: https://css.master.co/docs/breakpoints (fetched 2026-08-29T10:47:26.725481+00:00, sha a55906acf4a8)
  - site_page: https://css.master.co/docs/syntax-tutorial (fetched 2026-08-29T10:47:26.728681+00:00, sha 589d8fb554af)
  - site_page: https://css.master.co/docs/customization (fetched 2026-08-29T10:47:26.731250+00:00, sha c86946a7f2ce)
  - site_page: https://css.master.co/docs/hybrid-rendering (fetched 2026-08-29T10:47:26.733152+00:00, sha cc3d1dd45a81)
  - site_page: https://css.master.co/docs/developer-tools (fetched 2026-08-29T10:47:26.735107+00:00, sha 68d556c74108)
- Data as of 2026-08-30T08:39:29.467469+00:00.