clean-css

library5.3.3jsnpmunverified

A well-tested, fast and efficient CSS minifier for Node.js and browsers. Version 5.3.3 (stable) is released with patch updates over v5.3 (latest major). Clean-css outperforms many alternatives (cssnano, csso) in benchmarks, offering fine-grained optimization levels (0-2), compatibility modes (IE, standards), and source map support. It uses a highly modular plugin system and supports CLI, JavaScript API, and streaming. Engines require Node >= 10.0.

serialization

npm install clean-css

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · CLEAN-CSS

clean-css

serializationjavascriptv5.3.3

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

CleanCSS

✓ import CleanCSS from 'clean-css'

✗ import { CleanCSS } from 'clean-css'

The library exports a default class; named import does not work. For CommonJS: const CleanCSS = require('clean-css').

CleanCSS (CommonJS)

✓ const CleanCSS = require('clean-css')

✗ const { CleanCSS } = require('clean-css')

Default export. Destructuring from require is incorrect.

minify

✓ const CleanCSS = require('clean-css'); const output = new CleanCSS(options).minify(input)

✗ CleanCSS.minify(input, options)

minify() is an instance method, not static.

Basic usage: instantiate CleanCSS with options, call minify() on a CSS string, and log the minified output.

cleancss --version

Debug

Known issues

breakingSwitched to ES module exports. CommonJS require() no longer works.

fix

Use dynamic import or ensure package is CJS-compatible. For v5, CommonJS require still works, but future versions may drop it.

affects: >=5.0.0

deprecatedReturn type changed from object with .styles to object with .styles (removed .sourceMap, .errors, .warnings in same object).

fix

Check output.styles instead of output.minified; errors in output.errors array.

affects: >=5.0.0

gotchaminify() is synchronous. For large files, use Promise interface with .minify() returns a Promise if option 'returnPromise' is true.

fix

Set options.returnPromise = true and await the call.

affects: >=4.0.0

gotchaCSS custom properties (variables) not optimized by default.

fix

Use level 1's variableValueOptimizers option to enable variable optimization.

affects: <5.3.0

breakingLevel 2 optimizations no longer merge selectors from different media queries by default.

fix

Set options.level[2].mergeMedia = true to restore old behavior.

affects: >=4.0.0

deprecatedSemantic merge option removed.

fix

Use Level 2 'restructureRules' or 'mergeSemantically' options (check docs).

affects: >=5.0.0

Errors

Common errors & fixes

Cannot find module 'clean-css'

clean-css not installed or incorrect import path.

fix

Run 'npm install clean-css' and use 'require('clean-css')' or 'import CleanCSS from 'clean-css''.

CleanCSS is not a constructor

Using import { CleanCSS } instead of import CleanCSS (default import).

fix

Use 'import CleanCSS from 'clean-css'' or CommonJS require.

output.minified is undefined

In v5+, output object key is 'styles' not 'minified'.

fix

Access 'output.styles' instead of 'output.minified'.

TypeError: Cannot read property 'styles' of undefined

minify() might have thrown error or invalid input.

fix

Call minify on a valid CSS string; check output.errors for details.

Upgrade

Version history

5.3.3latest on npm

Audit

Dependencies

source-mapoptionalSource map generation requires the source-map module. Optional if source maps not needed.

Agent activity

7 hits · last 30 days

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Resources

githubhttps://github.com/clean-css/clean-css ↗

packagehttps://www.npmjs.com/package/clean-css ↗

homepagehttps://clean-css.github.io/ ↗