# css/csso

CSS minifier with structural optimizations

Repository: https://github.com/css/csso
Canonical: https://ross.abutalabs.com/products/csso
Homepage: https://css.github.io/csso/csso.html
Language: JavaScript
License: MIT
License Family: permissive
Topics: css-minifier, css, minifier, usage-data, fast
Last push: 2024-06-21T16:11:18+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 5678, "days_push": 803, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3788, forks 188 (observed 2026-08-28T04:08:18.657943+00:00)

## What it is
CSSO is a JavaScript CSS minifier that performs cleaning, compression, and structural restructuring of stylesheets via AST transformations built on CSSTree. It runs in Node.js and browsers and can emit source maps.

## Use cases
- minify css files for production
- reduce stylesheet size with structural optimizations
- compress css in a build pipeline
- minify css in the browser
- generate source maps while minifying css

## When to choose
- you need aggressive CSS minification with rule merging and restructuring
- you want a programmable AST-based minifier in Node.js or the browser
- you need source map support during minification

## When to avoid
- you only need simple whitespace stripping without restructuring
- you need minification for languages other than CSS
- you require a guaranteed stable internal AST API

## Facets
- artifact type: library
- maturity: stable
- function: compression, parser, developer-tools
- domain: web-development, frontend
- platform: browser, cross-platform
- tags: css-minifier, css-optimization, ast-based, source-map, build-pipeline, css, nodejs

## Member repositories
- css/csso (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:18.657943+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 2026-08-29T18:27:27.811775+00:00, confidence not recorded.
  - readme: https://github.com/css/csso (fetched 2026-08-28T04:08:18.657943+00:00, sha 8c052b54a22a)
  - homepage: https://css.github.io/csso/csso.html (fetched 2026-08-29T09:22:18.163137+00:00, sha 3ebba4f1b1c9)
  - registry_npm: https://registry.npmjs.org/csso (fetched 2026-08-29T09:22:18.171942+00:00, sha 469636215432)
- Data as of 2026-08-30T08:39:29.467469+00:00.