postcss

What is postcss?

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

What are postcss's main functionalities?

Autoprefixing

Automatically adds vendor prefixes to CSS rules using values from Can I Use. It is recommended by Google and used in Twitter and Alibaba.

postcss([ require('autoprefixer') ]).process(css).then(result => { result.warnings().forEach(warn => { console.warn(warn.toString()); }); console.log(result.css); });

CSS Variables

Transforms CSS Custom Properties (CSS variables) syntax into a static representation that can be understood by browsers that do not support this feature.

postcss([ require('postcss-custom-properties') ]).process(css).then(result => { console.log(result.css); });

CSS Nesting

Allows you to nest one style rule inside another, following the CSS Nesting Module Level 3 specification.

postcss([ require('postcss-nesting') ]).process(css).then(result => { console.log(result.css); });

Minification

A modular minifier, built on top of the PostCSS ecosystem. It is used to minimize CSS for better performance.

postcss([ require('cssnano') ]).process(css).then(result => { console.log(result.css); });

Future CSS Syntax

Allows you to use future CSS features today. It polyfills CSS features that are not yet fully supported in browsers.

postcss([ require('postcss-preset-env') ]).process(css).then(result => { console.log(result.css); });

Other packages similar to postcss

sass

Sass is a mature, stable, and powerful professional grade CSS extension language. It provides mechanisms such as variables, nesting, and mixins, which are not present in standard CSS. Unlike PostCSS, which uses JavaScript plugins, Sass has its own syntax and compiles to standard CSS.

less

Less is a backward-compatible language extension for CSS. It also allows variables, mixins, functions and many other techniques that allow you to make CSS more maintainable and extendable. Less is similar to Sass and differs from PostCSS in that it offers a different syntax and set of features.

stylus

Stylus is a preprocessor that serves as a more robust and feature-rich alternative to CSS. It supports both an indented syntax and regular CSS style. Stylus provides significant flexibility and feature parity with Sass and Less but with a different syntax and feature set compared to PostCSS.

README

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.

PostCSS takes a CSS file and provides an API to analyze and modify its rules (by transforming them into an Abstract Syntax Tree). This API can then be used by plugins to do a lot of useful things, e.g., to find errors automatically, or to insert vendor prefixes.

Support / Discussion: Gitter
Twitter account: @postcss
VK.com page: postcss
中文翻译: docs/README-cn.md

For PostCSS commercial support (consulting, improving the front-end culture of your company, PostCSS plugins), contact Evil Martians at [e-mail].

Sponsorship

PostCSS needs your support. We are accepting donations at Open Collective.

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-preset-env allows you to use future CSS features today.

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.
• postcss-utilities includes the most commonly used shortcuts and helpers.
• 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

• postcss-rtl combines both-directional (left-to-right and right-to-left) styles in one CSS file.
• cssnano is a modular CSS minifier.
• lost is a feature-rich calc() grid system.
• 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-syntax switch syntax automatically by file extensions.
• postcss-html parsing styles in <style> tags of HTML-like files.
• postcss-markdown parsing styles in code blocks of Markdown files.
• postcss-jsx parsing CSS in template / object literals of source files.
• postcss-styled parsing CSS in template literals of source files.
• postcss-scss allows you to work with SCSS (but does not compile SCSS to CSS).
• postcss-sass allows you to work with Sass (but does not compile Sass to CSS).
• postcss-less allows you to work with Less (but does not compile LESS to CSS).
• postcss-less-engine allows you to work with Less (and DOES compile LESS to CSS using true Less.js evaluation).
• 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

More articles and videos you can find on awesome-postcss list.

Books

• Mastering PostCSS for Web Design by Alex Libby, Packt. (June 2016)

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.

CSS-in-JS

The best way to use PostCSS with CSS-in-JS is astroturf. Add its loader to your webpack.config.js:

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: ['style-loader', 'postcss-loader'],
      },
      {
        test: /\.jsx?$/,
        use: ['babel-loader', 'astroturf/loader'],
      }
    ]
  }
}

Then create postcss.config.js:

module.exports = {
  plugins: [
    require('autoprefixer'),
    require('postcss-nested')
  ]
}

Parcel

Parcel has built-in PostCSS support. It already uses Autoprefixer and cssnano. If you want to change plugins, create postcss.config.js in project’s root:

module.exports = {
  plugins: [
    require('autoprefixer'),
    require('postcss-nested')
  ]
}

Parcel will even automatically install these plugins for you.

Please, be aware of the several issues in Version 1. Notice, Version 2 may resolve the issues via issue #2157.

Webpack

Use postcss-loader in webpack.config.js:

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        exclude: /node_modules/,
        use: [
          {
            loader: 'style-loader',
          },
          {
            loader: 'css-loader',
            options: {
              importLoaders: 1,
            }
          },
          {
            loader: 'postcss-loader'
          }
        ]
      }
    ]
  }
}

Then create postcss.config.js:

module.exports = {
  plugins: [
    require('precss'),
    require('autoprefixer')
  ]
}

Gulp

Use gulp-postcss and gulp-sourcemaps.

gulp.task('css', () => {
  const postcss    = require('gulp-postcss')
  const sourcemaps = require('gulp-sourcemaps')

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

npm Scripts

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

postcss --use autoprefixer -o main.css css/*.css

Browser

If you want to compile CSS string in browser (for instance, in live edit tools like CodePen), just use Browserify or webpack. They will pack PostCSS and plugins files into a single file.

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

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

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

Deno

PostCSS also supports Deno:

import postcss from 'https://deno.land/x/postcss/mod.js'
import autoprefixer from 'https://dev.jspm.io/autoprefixer'

const result = await postcss([autoprefixer]).process(css)

Runners

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

JS API

For other environments, you can use the JS API:

const autoprefixer = require('autoprefixer')
const postcss = require('postcss')
const precss = require('precss')
const fs = require('fs')

fs.readFile('src/app.css', (err, css) => {
  postcss([precss, autoprefixer])
    .process(css, { from: 'src/app.css', to: 'dest/app.css' })
    .then(result => {
      fs.writeFile('dest/app.css', result.css, () => true)
      if ( result.map ) {
        fs.writeFile('dest/app.css.map', result.map, () => true)
      }
    })
})

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).

Treat Warnings as Errors

In some situations it might be helpful to fail the build on any warning from PostCSS or one of its plugins. This guarantees that no warnings go unnoticed, and helps to avoid bugs. While there is no option to enable treating warnings as errors, it can easily be done by adding postcss-fail-on-warn plugin in the end of PostCSS plugins:

module.exports = {
  plugins: [
    require('autoprefixer'),
    require('postcss-fail-on-warn')
  ]
}

Editors & IDE Integration

VS Code

• csstools.postcss adds support for PostCSS, postcss-preset-env and CSS Modules.

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.

Vim

• postcss.vim adds PostCSS highlight.

WebStorm

WebStorm 2016.3 has built-in PostCSS support.

Security Contact

To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.

For Enterprise

Available as part of the Tidelift Subscription.

The maintainers of postcss and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. Learn more.