clean-css
Advanced tools
Package description
clean-css is a fast and efficient CSS optimizer for Node.js and the web. It minifies CSS by removing whitespace, comments, and unnecessary characters, merging identical rules, and applying other optimization techniques. It can be used to reduce the size of CSS files, which can lead to faster page load times and improved performance.
Minification
This feature allows you to minify CSS by removing unnecessary characters and whitespace, which results in smaller file sizes.
const CleanCSS = require('clean-css');
new CleanCSS().minify('a { font-weight: bold; }', function (error, output) {
console.log(output.styles);
});Source Map Generation
clean-css can generate source maps for the minified CSS, which is useful for debugging minified code in the browser.
const CleanCSS = require('clean-css');
new CleanCSS({ sourceMap: true, sourceMapInlineSources: true }).minify({ 'styles.css': { styles: 'a { color: #000 }' } }, function (error, output) {
console.log(output.sourceMap.toString());
});Merging of Identical CSS Rules
This feature merges identical CSS rules into one to reduce file size and redundancy in the code.
const CleanCSS = require('clean-css');
new CleanCSS().minify('a { color: red; } a { color: red; }', function (error, output) {
console.log(output.styles);
});Optimizing CSS Properties
clean-css can optimize CSS properties, such as converting hex color codes to shorter names when possible.
const CleanCSS = require('clean-css');
new CleanCSS().minify('a { color: #FF0000; }', function (error, output) {
console.log(output.styles);
});cssnano is a modular CSS minifier that utilizes PostCSS. It offers optimizations like reducing calc() references, z-index rebasing, and discarding unused at-rules. Compared to clean-css, cssnano provides a plugin system and can be more configurable due to its modular nature.
uglifycss is a simple CSS minifier that works both in Node.js and the browser. It is less feature-rich compared to clean-css and does not support source maps, but it is straightforward to use for basic minification tasks.
csso (CSS Optimizer) is a CSS minifier with structural optimizations. It can restructure CSS rules to reduce file size and also merge selectors and properties. csso is known for its aggressive optimization techniques, which sometimes can be more efficient than clean-css, but may also require careful testing to ensure the final CSS behaves as expected.
Readme
Clean-css is a node.js library for minifying CSS files. It does the same job as YUI Compressor's CSS minifier, but much faster thanks to many speed optimizations and node.js' V8 engine.
node 0.6.0+ on UN*X (fully tested on OS X 10.6+ and CentOS)
node 0.8.0+ on Windows
npm install clean-css
Clean-css accepts the following command line arguments (please make sure you use <source-file> as the
very last argument to avoid potential issues):
cleancss [options] <source-file>
-h, --help output usage information-v, --version output the version number-e, --remove-empty Remove empty declarations (e.g. a{})-b, --keep-line-breaks Keep line breaks--s0 Remove all special comments (i.e. /*! special comment */)--s1 Remove all special comments but the first one-o, --output [output-file] Use [output-file] as output instead of stdoutTo minify a public.css file into public-min.css do:
cleancss -o public-min.css public.css
To minify the same public.css into the standard output skip the -o parameter:
cleancss public.css
More likely you would like to concatenate a couple of files. If you are on a Unix-like system:
cat one.css two.css three.css | cleancss -o merged-and-minified.css
On Windows:
type one.css two.css three.css | cleancss -o merged-and-minified.css
Or even gzip the result at once:
cat one.css two.css three.css | cleancss | gzip -9 -c > merged-minified-and-gzipped.css.gz
var cleanCSS = require('clean-css');
var source = "a{font-weight:bold;}";
var minimized = cleanCSS.process(source);
Process method accepts a hash as a second parameter, i.e.,
cleanCSS.process(source, options) with the following options available:
keepSpecialComments - * for keeping all (default), 1 for keeping first one, 0 for removing allkeepBreaks - whether to keep line breaks (default is false)removeEmpty - whether to remove empty elements (default is false)debug - turns on debug mode measuring time spent on cleaning up
(run npm run bench to see example)First clone the source, then run:
npm run bench for clean-css benchmarks (see test/bench.js for details)npm run check to check JS sources with JSHintnpm test for the test suiteUse the /*! notation instead of the standard one /*:
/*!
Important comments included in minified output.
*/
Clean-css is released under the MIT License.
FAQs
A well-tested CSS minifier
We found that clean-css demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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