PostCSS

PostCSS is a tool for transforming styles with JS plugins. These plugins can lint your CSS, support variables and mixins, transpile future CSS syntax, inline images, and more.

PostCSS is used by industry leaders including Wikipedia, Twitter, Alibaba, and JetBrains. The Autoprefixer PostCSS plugin is one of the most popular CSS processors.

Twitter account: @postcss. VK.com page: postcss. Support / Discussion: Gitter.

Plugins

Currently, PostCSS has more than 200 plugins. You can find all of the plugins in the plugins list or in the searchable catalog. Below is a list of our favorite plugins — the best demonstrations of what can be built on top of PostCSS.

If you have any new ideas, PostCSS plugin development is really easy.

Solve Global CSS Problem

• postcss-use allows you to explicitly set PostCSS plugins within CSS and execute them only for the current file.
• postcss-modules and react-css-modules automatically isolate selectors within components.
• postcss-autoreset is an alternative to using a global reset that is better for isolatable components.
• postcss-initial adds all: initial support, which resets all inherited styles.
• cq-prolyfill adds container query support, allowing styles that respond to the width of the parent.

Use Future CSS, Today

• autoprefixer adds vendor prefixes, using data from Can I Use.
• postcss-cssnext allows you to use future CSS features today (includes autoprefixer).

Better CSS Readability

• precss contains plugins for Sass-like features, like variables, nesting, and mixins.
• postcss-sorting sorts the content of rules and at-rules.
• short adds and extends numerous shorthand properties.

Images and Fonts

• postcss-assets inserts image dimensions and inlines files.
• postcss-sprites generates image sprites.
• font-magician generates all the @font-face rules needed in CSS.
• postcss-inline-svg allows you to inline SVG and customize its styles.
• postcss-write-svg allows you to write simple SVG directly in your CSS.

Linters

• stylelint is a modular stylesheet linter.
• stylefmt is a tool that automatically formats CSS according stylelint rules.
• doiuse lints CSS for browser support, using data from Can I Use.
• colorguard helps you maintain a consistent color palette.

Other

• lost is a feature-rich calc() grid system.
• cssnano is a modular CSS minifier.
• rtlcss mirrors styles for right-to-left locales.

Syntaxes

PostCSS can transform styles in any syntax, not just CSS. If there is not yet support for your favorite syntax, you can write a parser and/or stringifier to extend PostCSS.

• sugarss is a indent-based syntax like Sass or Stylus.
• postcss-scss allows you to work with SCSS (but does not compile SCSS to CSS).
• postcss-less allows you to work with Less (but does not compile LESS to CSS).
• postcss-js allows you to write styles in JS or transform React Inline Styles, Radium or JSS.
• postcss-safe-parser finds and fixes CSS syntax errors.
• midas converts a CSS string to highlighted HTML.

Articles

• Some things you may think about PostCSS… and you might be wrong
• What PostCSS Really Is; What It Really Does
• PostCSS Guides

Usage

You can start using PostCSS in just two steps:

1. Find and add PostCSS extensions for your build tool.
2. Select plugins and add them to your PostCSS process.

Gulp

Use gulp-postcss and gulp-sourcemaps.

gulp.task('css', function () {
    var postcss    = require('gulp-postcss');
    var sourcemaps = require('gulp-sourcemaps');

    return gulp.src('src/**/*.css')
        .pipe( sourcemaps.init() )
        .pipe( postcss([ require('autoprefixer'), require('precss') ]) )
        .pipe( sourcemaps.write('.') )
        .pipe( gulp.dest('build/') );
});

Webpack

Use postcss-loader:

module.exports = {
    module: {
        loaders: [
            {
                test:   /\.css$/,
                loader: "style-loader!css-loader!postcss-loader"
            }
        ]
    },
    postcss: function () {
        return [require('autoprefixer'), require('precss')];
    }
}

npm run / CLI

To use PostCSS from your command-line interface or with npm scripts there is postcss-cli.

postcss --use autoprefixer -c options.json -o main.css css/*.css

CSS-in-JS

To apply PostCSS plugins to React Inline Styles, JSS, Radium and other CSS-in-JS, you can use postcss-js and transforms style objects.

var postcss  = require('postcss-js');
var prefixer = postcss.sync([ require('autoprefixer') ]);

prefixer({ display: 'flex' }); //=> { display: ['-webkit-box', '-webkit-flex', '-ms-flexbox', 'flex'] }

Runners

• Grunt: grunt-postcss
• HTML: posthtml-postcss
• Stylus: poststylus
• Rollup: rollup-plugin-postcss
• Brunch: postcss-brunch
• Broccoli: broccoli-postcss
• Meteor: postcss
• ENB: enb-postcss
• Fly: fly-postcss
• Start: start-postcss
• Connect/Express: postcss-middleware

JS API

For other environments, you can use the JS API:

var postcss = require('postcss');
postcss([ require('autoprefixer'), require('cssnano') ])
    .process(css, { from: 'src/app.css', to: 'app.css' })
    .then(function (result) {
        fs.writeFileSync('app.css', result.css);
        if ( result.map ) fs.writeFileSync('app.css.map', result.map);
    });

Read the PostCSS API documentation for more details about the JS API.

All PostCSS runners should pass PostCSS Runner Guidelines.

Options

Most PostCSS runners accept two parameters:

• An array of plugins.
• An object of options.

Common options:

• syntax: an object providing a syntax parser and a stringifier.
• parser: a special syntax parser (for example, SCSS).
• stringifier: a special syntax output generator (for example, Midas).
• map: source map options.
• from: the input file name (most runners set it automatically).
• to: the output file name (most runners set it automatically).

Node.js 0.10 and the Promise API

If you want to run PostCSS in Node.js 0.10, add the Promise polyfill:

require('es6-promise').polyfill();
var postcss = require('postcss');

IDE Integration

Atom

• language-postcss adds PostCSS and [SugarSS] highlight.
• source-preview-postcss previews your output CSS in a separate, live pane.

Sublime Text

• Syntax-highlighting-for-PostCSS adds PostCSS highlight.