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postcss-loader
Loader to process CSS with PostCSS.
Getting Started
To begin, you'll need to install postcss-loader and postcss:
npm install --save-dev postcss-loader postcss
Then add the plugin to your webpack config. For example:
file.js
import css from "file.css";
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
Alternative use with config files:
postcss.config.js
module.exports = {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
};
The loader automatically searches for configuration files.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader", "postcss-loader"],
},
],
},
};
And run webpack via your preferred method.
Options
| Name | Type | Default | Description |
|---|---|---|---|
execute |
{Boolean} |
undefined |
Enable PostCSS Parser support in CSS-in-JS |
postcssOptions |
{Object|Function} |
defaults values for Postcss.process |
Set PostCSS options and plugins |
sourceMap |
{Boolean} |
compiler.devtool |
Enables/Disables generation of source maps |
execute
Type: Boolean Default: undefined
If you use JS styles the postcss-js parser, add the execute option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.style.js$/,
use: [
"style-loader",
{
loader: "css-loader",
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "postcss-js",
},
execute: true,
},
},
],
},
],
},
};
postcssOptions
Type: Object|Function Default: undefined
Allows to set PostCSS options and plugins.
All PostCSS options are supported. There is the special config option for config files. How it works and how it can be configured is described below.
We recommend do not specify from, to and map options, because this can lead to wrong path in source maps. If you need source maps please use the sourcemap option.
Object
Setup plugins:
webpack.config.js (recommended)
const myOtherPostcssPlugin = require("postcss-my-plugin");
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
"postcss-import",
["postcss-short", { prefix: "x" }],
require.resolve("my-postcss-plugin"),
myOtherPostcssPlugin({ myOption: true }),
// Deprecated and will be removed in the next major release
{ "postcss-nested": { preserveEmpty: true } },
],
},
},
},
],
},
};
webpack.config.js (deprecated, will be removed in the next major release)
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: {
"postcss-import": {},
"postcss-short": { prefix: "x" },
},
},
},
},
],
},
};
Setup syntax:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `String`
syntax: "sugarss",
// Can be `Object`
syntax: require("sugarss"),
},
},
},
],
},
};
Setup parser:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `String`
parser: "sugarss",
// Can be `Object`
parser: require("sugarss"),
// Can be `Function`
parser: require("sugarss").parse,
},
},
},
],
},
};
Setup stringifier:
webpack.config.js
const Midas = require("midas");
const midas = new Midas();
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `String`
stringifier: "sugarss",
// Can be `Object`
stringifier: require("sugarss"),
// Can be `Function`
stringifier: midas.stringifier,
},
},
},
],
},
};
Function
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.(css|sss)$/i,
loader: "postcss-loader",
options: {
postcssOptions: (loaderContext) => {
if (/\.sss$/.test(loaderContext.resourcePath)) {
return {
parser: "sugarss",
plugins: [
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
}
return {
plugins: [
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
},
},
},
],
},
};
config
Type: Boolean|String Default: undefined
Allows to set options using config files. Options specified in the config file are combined with options passed to the loader, the loader options overwrite options from config.
Config Files
The loader will search up the directory tree for configuration in the following places:
- a
postcssproperty inpackage.json - a
.postcssrcfile in JSON or YAML format - a
.postcssrc.json,.postcssrc.yaml,.postcssrc.yml,.postcssrc.js, or.postcssrc.cjsfile - a
postcss.config.jsorpostcss.config.cjsCommonJS module exporting an object (recommended)
Examples of Config Files
Using Object notation:
postcss.config.js (recommend)
module.exports = {
// You can specify any options from https://postcss.org/api/#processoptions here
// parser: 'sugarss',
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
Using Function notation:
postcss.config.js (recommend)
module.exports = (api) => {
// `api.file` - path to the file
// `api.mode` - `mode` value of webpack, please read https://webpack.js.org/configuration/mode/
// `api.webpackLoaderContext` - loader context for complex use cases
// `api.env` - alias `api.mode` for compatibility with `postcss-cli`
// `api.options` - the `postcssOptions` options
if (/\.sss$/.test(api.file)) {
return {
// You can specify any options from https://postcss.org/api/#processoptions here
parser: "sugarss",
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
}
return {
// You can specify any options from https://postcss.org/api/#processoptions here
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
};
postcss.config.js (deprecated, will be removed in the next major release)
module.exports = {
// You can specify any options from https://postcss.org/api/#processoptions here
// parser: 'sugarss',
plugins: {
// Plugins for PostCSS
"postcss-short": { prefix: "x" },
"postcss-preset-env": {},
},
};
Config Cascade
You can use different postcss.config.js files in different directories. Config lookup starts from path.dirname(file) and walks the file tree upwards until a config file is found.
|– components
| |– component
| | |– index.js
| | |– index.png
| | |– style.css (1)
| | |– postcss.config.js (1)
| |– component
| | |– index.js
| | |– image.png
| | |– style.css (2)
|
|– postcss.config.js (1 && 2 (recommended))
|– webpack.config.js
|
|– package.json
After setting up your postcss.config.js, add postcss-loader to your webpack.config.js. You can use it standalone or in conjunction with css-loader (recommended).
Use it before css-loader and style-loader, but after other preprocessor loaders like e.g sass|less|stylus-loader, if you use any (since webpack loaders evaluate right to left/bottom to top).
webpack.config.js (recommended)
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
"style-loader",
{
loader: "css-loader",
options: {
importLoaders: 1,
},
},
"postcss-loader",
],
},
],
},
};
Boolean
Enables/Disables autoloading config.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
config: false,
},
},
},
],
},
};
String
Allows to specify the path to the config file.
webpack.config.js
const path = require("path");
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
config: path.resolve(__dirname, "custom.config.js"),
},
},
},
],
},
};
sourceMap
Type: Boolean Default: depends on the compiler.devtool value
By default generation of source maps depends on the devtool option. All values enable source map generation except eval and false value.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader", options: { sourceMap: true } },
{ loader: "postcss-loader", options: { sourceMap: true } },
{ loader: "sass-loader", options: { sourceMap: true } },
],
},
],
},
};
Alternative setup:
webpack.config.js
module.exports = {
devtool: "source-map",
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader" },
{ loader: "postcss-loader" },
{ loader: "sass-loader" },
],
},
],
},
};
Examples
SugarSS
You'll need to install sugarss:
npm install --save-dev sugarss
Using SugarSS syntax.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "sugarss",
},
},
},
],
},
],
},
};
Autoprefixer
You'll need to install autoprefixer:
npm install --save-dev autoprefixer
Add vendor prefixes to CSS rules using autoprefixer.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"autoprefixer",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
⚠️ postcss-preset-envincludesautoprefixer, so adding it separately is not necessary if you already use the preset. More information
PostCSS Preset Env
You'll need to install postcss-preset-env:
npm install --save-dev postcss-preset-env
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
CSS Modules
What is CSS Modules? Please read.
No additional options required on the postcss-loader side. To make them work properly, either add the css-loader’s importLoaders option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
modules: true,
importLoaders: 1,
},
},
"postcss-loader",
],
},
],
},
};
CSS-in-JS and postcss-js
You'll need to install postcss-js:
npm install --save-dev postcss-js
If you want to process styles written in JavaScript, use the postcss-js parser.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.style.js$/,
use: [
"style-loader",
{
loader: "css-loader",
options: {
importLoaders: 2,
},
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "postcss-js",
},
execute: true,
},
},
"babel-loader",
],
},
],
},
};
As result you will be able to write styles in the following way
import colors from "./styles/colors";
export default {
".menu": {
color: colors.main,
height: 25,
"&_link": {
color: "white",
},
},
};
⚠️ If you are using Babel you need to do the following in order for the setup to work
- Add
babel-plugin-add-module-exportsto your configuration.- You need to have only one default export per style module.
Extract CSS
Using mini-css-extract-plugin.
webpack.config.js
const isProductionMode = process.env.NODE_ENV === "production";
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
mode: isProductionMode ? "production" : "development",
module: {
rules: [
{
test: /\.css$/,
use: [
isProductionMode ? MiniCssExtractPlugin.loader : "style-loader",
"css-loader",
"postcss-loader",
],
},
],
},
plugins: [
new MiniCssExtractPlugin({
filename: isProductionMode ? "[name].[contenthash].css" : "[name].css",
}),
],
};
Emit assets
To write a asset from PostCSS plugin to the webpack, need to add a message in result.messages.
The message should contain the following fields:
type=asset- Message type (require, should be equalasset)file- file name (require)content- file content (require)sourceMap- sourceMapinfo- asset info
webpack.config.js
const customPlugin = () => (css, result) => {
result.messages.push({
type: "asset",
file: "sprite.svg",
content: "<svg>...</svg>",
});
};
const postcssPlugin = postcss.plugin("postcss-assets", customPlugin);
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [postcssPlugin()],
},
},
},
],
},
],
},
};
Add dependencies
The dependencies are necessary for webpack to understand when it needs to run recompilation on the changed files.
There are two way to add dependencies:
- (Recommended). The plugin may emit messages in
result.messages.
The message should contain the following fields:
type=dependency- Message type (require, should be equaldependency)file- absolute file path (require)
webpack.config.js
const path = require("path");
const customPlugin = () => (css, result) => {
result.messages.push({
type: "dependency",
file: path.resolve(__dirname, "path", "to", "file"),
});
};
const postcssPlugin = postcss.plugin("postcss-assets", customPlugin);
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [postcssPlugin()],
},
},
},
],
},
],
},
};
- Pass
loaderContextin plugin.
webpack.config.js
const path = require("path");
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
config: path.resolve(__dirname, "path/to/postcss.config.js"),
},
},
},
],
},
],
},
};
postcss.config.js
module.exports = (api) => ({
plugins: [
require("path/to/customPlugin")({
loaderContext: api.webpackLoaderContext,
}),
],
});
customPlugin.js
const path = require("path");
const customPlugin = (loaderContext) => (css, result) => {
loaderContext.webpack.addDependency(
path.resolve(__dirname, "path", "to", "file")
);
};
module.exports = postcss.plugin("postcss-assets", customPlugin);
Contributing
Please take a moment to read our contributing guidelines if you haven't yet done so.
