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 fast and efficient Node.js library for minifying CSS files.
According to tests it is one of the best available.
Node.js 0.8.0+ (tested on CentOS, Ubuntu, OS X 10.6+, and Windows 7+)
npm install clean-css
npm update clean-css
or point package.json to version 2.x. That's it!
Update clean-css as for CLI above.
Then change your JavaScript code from:
var minimized = CleanCSS.process(source, options);
into
var minimized = new CleanCSS(options).minify(source);
And you are done.
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, [source-file, ...]
-h, --help Output usage information
-v, --version Output the version number
-b, --keep-line-breaks Keep line breaks
--s0 Remove all special comments, i.e. /*! comment */
--s1 Remove all special comments but the first one
-r, --root [root-path] A root path to which resolve absolute @import rules
and rebase relative URLs
-o, --output [output-file] Use [output-file] as output instead of STDOUT
-s, --skip-import Disable @import processing
--skip-rebase Disable URLs rebasing
--skip-advanced Disable advanced optimizations - selector & property merging,
reduction, etc.
--skip-aggressive-merging Disable properties merging based on their order
--rounding-precision [value] Rounding precision, defaults to 2
-c, --compatibility [ie7|ie8] Force compatibility mode
-d, --debug Shows debug information (minification time & compression efficiency)
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 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 = new CleanCSS().minify(source);
CleanCSS constructor accepts a hash as a parameter, i.e.,
new CleanCSS(options).minify(source) with the following options available:
keepSpecialComments - * for keeping all (default), 1 for keeping first one only, 0 for removing allkeepBreaks - whether to keep line breaks (default is false)benchmark - turns on benchmarking mode measuring time spent on cleaning up
(run npm run bench to see example)root - path to resolve absolute @import rules and rebase relative URLsrelativeTo - path with which to resolve relative @import rules and URLsprocessImport - whether to process @import rulesnoRebase - whether to skip URLs rebasingnoAdvanced - set to true to disable advanced optimizations - selector & property merging, reduction, etc.compatibility - Force compatibility mode to ie7 or ie8. Defaults to not set.debug - set to true to get minification statistics under stats property (see test/custom-test.js for examples)For a tutorial how to use Grunt, Gulp, Broccoli or Brunch with clean-css, read Addy Osmani's "Spring cleaning unused CSS".
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 suitenpm test).npm run check) and follow all other ones too.If you wonder where to add tests, go for:
test/unit-test.js if it's a simple scenariotest/data/... if it's a complex scenario (just add two files, input and expected output)test/binary-test.js if it's related to bin/cleancss binarytest/module-test.js if it's related to importing clean-css as a moduletest/protocol-imports-test.js if it fixes anything related to protocol @importsUse the /*! notation instead of the standard one /*:
/*!
Important comments included in minified output.
*/
Clean-css will handle it automatically for you (since version 1.1) in the following cases:
-o/--output to rebase URLs as relative to the output file.-r/--root to rebase URLs as absolute from the given root path.-r/--root takes precendence.relativeTo and target options for relative rebase (same as 1 in CLI).relativeTo and root options for absolute rebase (same as 2 in CLI).root takes precendence over target as in CLI.@import processing, namely introducing the --skip-import /
processImport options.@import processing inside comments.sys package.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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