What is clean-css?
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.
What are clean-css's main functionalities?
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);
});
Other packages similar to clean-css
cssnano
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
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
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.
What is clean-css?
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 the node.js itself.
Usage
What are the requirements?
node 0.6.0+ on *nix (fully tested on OS X 10.6+ and CentOS)
node 0.8.0+ on Windows
How to install clean-css?
npm install clean-css
How to use clean-css?
To minify a public.css file into public-min.css do:
cleancss -o public-min.css public.css
To minify the same public.css into standard output skip the -o parameter:
cleancss public.css
Or more likely you would like to do something like this (if you are on *nix system):
cat one.css two.css three.css | cleancss -o merged-and-minified.css
Or even gzip it at once:
cat one.css two.css three.css | cleancss | gzip -9 -c > merged-minified-and-gzipped.css.gz
How to use clean-css programatically?
var cleanCSS = require('clean-css');
var source = "a{font-weight:bold;}";
var minimized = cleanCSS.process(source);
/*!
Important comments included in minified output.
*/
How to run clean-css tests?
First clone the source, then run:
npm test
on *nix systems. If you are under Windows then run:
./test.bat
Acknowledgments
- Vincent Voyer (@vvo) for a patch with better empty element regex and for inspiring us to do many performance improvements in 0.4 release.
- Isaac (@facelessuser) for pointing out a flaw in clean-css' stateless mode.
- Jan Michael Alonzo (@jmalonzo) for a patch removing node's old 'sys' package.
- @XhmikosR for suggesting new features: option to remove special comments and strip out url's parentheses.
License
Clean-css is released under the MIT license.