csso
Advanced tools
Package description
CSSO (CSS Optimizer) is a CSS minifier. It performs three kinds of optimizations: structural optimizations, reducing CSS size by merging blocks with identical properties, removing overridden properties, etc.; cleaning (removing unused @media rules, cutting out the comments, etc.); and compressing (transforming values to shorter forms, merging identical selectors, etc.). It can be used as a command-line tool or as a library.
Minification
Minifies CSS by removing whitespace, comments, and making other optimizations to reduce file size.
const csso = require('csso');
const minifiedCss = csso.minify('.test { color: #ff0000; }').css;Structural Optimization
Optimizes CSS structure by merging blocks with identical properties and removing overridden properties.
const csso = require('csso');
const optimizedCss = csso.minify('.test { color: red; } .test { font-size: 16px; }', { restructure: true }).css;Source Map Generation
Generates a source map that can be used to debug the minified CSS by mapping it back to the original sources.
const csso = require('csso');
const result = csso.minify('.test { color: red; }', { sourceMap: true });
const minifiedCss = result.css;
const map = result.map.toString();clean-css is a fast and efficient CSS optimizer for Node.js and the Web. It provides similar minification capabilities as CSSO but also offers advanced optimizations like restructuring.
uglifycss is a CSS minifier that aims to be fast and simple. It doesn't have as many features as CSSO, focusing mainly on removing whitespace and comments to compress CSS files.
purifycss is a tool to remove unused CSS. Unlike CSSO, which focuses on optimizing existing CSS, purifycss analyzes your content and CSS files to remove unused selectors.
Changelog
1.5.4 (January 27, 2016)
restructRuleset this time) with merge of rulesets when a ruleset with same specificity places between them (#264)@keyframes rulesets (until sure it's correct)Readme
CSSO (CSS Optimizer) is a CSS minimizer unlike others. In addition to usual minification techniques it can perform structural optimization of CSS files, resulting in smaller file size compared to other minifiers.
npm install -g csso
csso [input] [output] [options]
Options:
--debug [level] Output intermediate state of CSS during compression
-h, --help Output usage information
-i, --input <filename> Input file
-o, --output <filename> Output file (result outputs to stdout if not set)
--restructure-off Turns structure minimization off
--stat Output statistics in stderr
-v, --version Output version
Some examples:
> csso in.css out.css
> csso in.css
...output result in stdout...
> echo ".test { color: #ff0000; }" | csso
.test{color:red}
> cat source1.css source2.css | csso | gzip -9 -c > production.css.gz
Debug and statistics:
> echo '.test { color: #ff0000 }' | node bin/csso --stat >/dev/null
File: <stdin>
Original: 25 bytes
Compressed: 16 bytes (64.00%)
Saving: 9 bytes (36.00%)
Time: 12 ms
Memory: 0.346 MB
> echo '.test { color: green; color: #ff0000 } .foo { color: red }' | node bin/csso --debug
## parsing done in 10 ms
Compress block #1
(0.002ms) convertToInternal
(0.000ms) clean
(0.001ms) compress
(0.002ms) prepare
(0.000ms) initialRejoinRuleset
(0.000ms) rejoinAtrule
(0.000ms) disjoin
(0.000ms) buildMaps
(0.000ms) markShorthands
(0.000ms) processShorthand
(0.001ms) restructBlock
(0.000ms) rejoinRuleset
(0.000ms) restructRuleset
## compressing done in 9 ms
.foo,.test{color:red}
> echo '.test { color: green; color: #ff0000 } .foo { color: red }' | node bin/csso --debug 2
## parsing done in 8 ms
Compress block #1
(0.002ms) convertToInternal
.test{color:green;color:#ff0000}.foo{color:red}
(0.000ms) clean
.test{color:green;color:#ff0000}.foo{color:red}
(0.001ms) compress
.test{color:green;color:red}.foo{color:red}
...
(0.002ms) restructBlock
.test{color:red}.foo{color:red}
(0.001ms) rejoinRuleset
.foo,.test{color:red}
(0.000ms) restructRuleset
.foo,.test{color:red}
## compressing done in 13 ms
.foo,.test{color:red}
var csso = require('csso');
var compressed = csso.minify('.test { color: #ff0000; }');
console.log(compressed);
// .test{color:red}
// there are some options you can pass
var compressedWithOptions = csso.minify('.test { color: #ff0000; }', {
restructuring: false, // don't change css structure, i.e. don't merge declarations, rulesets etc
debug: true // show additional debug information:
// true or number from 1 to 3 (greater number - more details)
});
// you may do it step by step
var ast = csso.parse('.test { color: #ff0000; }');
ast = csso.compress(ast);
var compressed = csso.translate(ast, true);
console.log(compressed);
// .test{color:red}
May be outdated
FAQs
CSS minifier with structural optimisations
We found that csso demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 3 open source maintainers collaborating on the project.
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