mini-css-extract-plugin

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mini-css-extract-plugin

This plugin extracts CSS into separate files. It creates a CSS file per JS file which contains CSS. It supports On-Demand-Loading of CSS and SourceMaps.

It builds on top of a new webpack v4 feature (module types) and requires webpack 4 to work.

Compared to the extract-text-webpack-plugin:

- Async loading
- No duplicate compilation (performance)
- Easier to use
- Specific to CSS

Getting Started

To begin, you'll need to install mini-css-extract-plugin:

``bash
npm install --save-dev mini-css-extract-plugin
`

It's recommended to combine mini-css-extract-plugin with the css-loader

Then add the loader and the plugin to your webpack config. For example:

style.css

`css
body {
background: green;
}
`

component.js

`js
import './style.css';
`

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [new MiniCssExtractPlugin()],
module: {
rules: [
{
test: /\.css$/i,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
};
`

Options

$3

| Name | Type | Default | Description |
| :---------------------------------------------------------------: | :------------------: | :-----------------------------------: | :---------------------------------------------------------------------------- |
| filename | {String\|Function} | [name].css | This option determines the name of each output CSS file |
| chunkFilename | {String\|Function} | based on filename | This option determines the name of non-entry chunk files |
| ignoreOrder | {Boolean} | false | Remove Order Warnings |
| insert | {String\|Function} | document.head.appendChild(linkTag); | Inserts at the given position |
| attributes | {Object} | {} | Adds custom attributes to tag |
| linkType | {String\|Boolean} | text/css | Allows loading asynchronous chunks with a custom link type |
| experimentalUseImportModule | {Boolean} | false | Use an experimental webpack API to execute modules instead of child compilers |

#### filename

Type: String|Function
Default: [name].css

This option determines the name of each output CSS file.

Works like output.filename

#### chunkFilename

Type: String|Function
Default: based on filename

> i Specifying chunkFilename as a function is only available in webpack@5

This option determines the name of non-entry chunk files.

Works like output.chunkFilename

#### ignoreOrder

Type: Boolean
Default: false

Remove Order Warnings.
See examples below for details.

#### insert

Type: String|Function
Default: document.head.appendChild(linkTag);

By default, the mini-css-extract-plugin appends styles ( elements) to document.head of the current window.

However in some circumstances it might be necessary to have finer control over the append target or even delay link elements insertion.
For example this is the case when you asynchronously load styles for an application that runs inside of an iframe.
In such cases insert can be configured to be a function or a custom selector.

If you target an iframe make sure that the parent document has sufficient access rights to reach into the frame document and append elements to it.

##### String

Allows to setup custom query selector.
A new element will be inserted after the found item.

webpack.config.js

`js
new MiniCssExtractPlugin({
insert: '#some-element',
});
`

A new element will be inserted after the element with id some-element.

##### Function

Allows to override default behavior and insert styles at any position.

> ⚠ Do not forget that this code will run in the browser alongside your application. Since not all browsers support latest ECMA features like let, const, arrow function expression and etc we recommend you to use only ECMA 5 features and syntax.

> > ⚠ The insert function is serialized to string and passed to the plugin. This means that it won't have access to the scope of the webpack configuration module.

webpack.config.js

`js
new MiniCssExtractPlugin({
insert: function (linkTag) {
var reference = document.querySelector('#some-element');
if (reference) {
reference.parentNode.insertBefore(linkTag, reference);
}
},
});
`

A new element will be inserted before the element with id some-element.

#### attributes

Type: Object
Default: {}

If defined, the mini-css-extract-plugin will attach given attributes with their values on element.

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
attributes: {
id: 'target',
'data-target': 'example',
},
}),
],
module: {
rules: [
{
test: /\.css$/i,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
};
`

Note: It's only applied to dynamically loaded css chunks, if you want to modify link attributes inside html file, please using html-webpack-plugin

#### linkType

Type: String|Boolean
Default: text/css

This option allows loading asynchronous chunks with a custom link type, such as .

##### String

Possible values: text/css

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
linkType: 'text/css',
}),
],
module: {
rules: [
{
test: /\.css$/i,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
};
`

##### Boolean

false disables the link type attribute

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
linkType: false,
}),
],
module: {
rules: [
{
test: /\.css$/i,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
};
`

#### experimentalUseImportModule

Use an experimental webpack API to execute modules instead of child compilers.

This improves performance and memory usage a lot, but isn't as stable as the normal approach.

When combined with experiments.layers, this adds a layer option to the loader options to specify the layer of the css execution.

You need to have at least webpack 5.33.2.

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
experimentalUseImportModule: true,
}),
],
module: {
rules: [
{
test: /\.css$/i,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
};
`

$3

| Name | Type | Default | Description |
| :-----------------------------: | :------------------: | :--------------------------------: | :-------------------------------------------------------------------------------- |
| publicPath | {String\|Function} | webpackOptions.output.publicPath | Specifies a custom public path for the external resources like images, files, etc |
| emit | {Boolean} | true | If false, the plugin will extract the CSS but will not emit the file |
| esModule | {Boolean} | true | Use ES modules syntax |
| modules | {Object} | undefined | Configuration CSS Modules |

#### publicPath

Type: String|Function
Default: the publicPath in webpackOptions.output

Specifies a custom public path for the external resources like images, files, etc inside CSS.
Works like output.publicPath

##### String

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
publicPath: '/public/path/to/',
},
},
'css-loader',
],
},
],
},
};
`

##### Function

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
publicPath: (resourcePath, context) => {
return path.relative(path.dirname(resourcePath), context) + '/';
},
},
},
'css-loader',
],
},
],
},
};
`

#### emit

Type: Boolean
Default: true

If true, emits a file (writes a file to the filesystem). If false, the plugin will extract the CSS but will not emit the file.
It is often useful to disable this option for server-side packages.

#### esModule

Type: Boolean
Default: true

By default, mini-css-extract-plugin generates JS modules that use the ES modules syntax.
There are some cases in which using ES modules is beneficial, like in the case of module concatenation and tree shaking.

You can enable a CommonJS syntax using:

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [new MiniCssExtractPlugin()],
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
esModule: false,
},
},
'css-loader',
],
},
],
},
};
`

#### modules

Type: Object
Default: undefined

Configuration CSS Modules.

##### namedExport

Type: Boolean
Default: false

Enables/disables ES modules named export for locals.

> ⚠ Names of locals are converted to camelCase.

> ⚠ It is not allowed to use JavaScript reserved words in css class names.

> ⚠ Options esModule and modules.namedExport in css-loader and MiniCssExtractPlugin.loader should be enabled.

styles.css

`css
.foo-baz {
color: red;
}
.bar {
color: blue;
}
`

index.js

`js
import { fooBaz, bar } from './styles.css';

console.log(fooBaz, bar);
`

You can enable a ES module named export using:

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [new MiniCssExtractPlugin()],
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
esModule: true,
modules: {
namedExport: true,
},
},
},
{
loader: 'css-loader',
options: {
esModule: true,
modules: {
namedExport: true,
localIdentName: 'foo__[name]__[local]',
},
},
},
],
},
],
},
};
`

Examples

$3

For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
This can be achieved by using the mini-css-extract-plugin, because it creates separate css files.
For development mode (including webpack-dev-server) you can use style-loader, because it injects CSS into the DOM using multiple and works faster.

> i Do not use together style-loader and mini-css-extract-plugin.

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const devMode = process.env.NODE_ENV !== 'production';

module.exports = {
module: {
rules: [
{
test: /\.(sa|sc|c)ss$/,
use: [
devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
'css-loader',
'postcss-loader',
'sass-loader',
],
},
],
},
plugins: [].concat(devMode ? [] : [new MiniCssExtractPlugin()]),
};
`

$3

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// all options are optional
filename: '[name].css',
chunkFilename: '[id].css',
ignoreOrder: false, // Enable to remove warnings about conflicting order
}),
],
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
// you can specify a publicPath here
// by default it uses publicPath in webpackOptions.output
publicPath: '../',
},
},
'css-loader',
],
},
],
},
};
`

$3

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {
publicPath: (resourcePath, context) => {
// publicPath is the relative path of the resource to the context
// e.g. for ./css/admin/main.css the publicPath will be ../../
// while for ./css/main.css the publicPath will be ../
return path.relative(path.dirname(resourcePath), context) + '/';
},
},
},
'css-loader',
],
},
],
},
};
`

$3

This plugin should not be used with style-loader in the loaders chain.

Here is an example to have both HMR in development and your styles extracted in a file for production builds.

(Loaders options left out for clarity, adapt accordingly to your needs.)

You should not use HotModuleReplacementPlugin plugin if you are using a webpack-dev-server.
webpack-dev-server enables / disables HMR using hot option.

webpack.config.js

`js
const webpack = require('webpack');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const devMode = process.env.NODE_ENV !== 'production';

const plugins = [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: devMode ? '[name].css' : '[name].[contenthash].css',
chunkFilename: devMode ? '[id].css' : '[id].[contenthash].css',
}),
];
if (devMode) {
// only enable hot in development
plugins.push(new webpack.HotModuleReplacementPlugin());
}

module.exports = {
plugins,
module: {
rules: [
{
test: /\.(sa|sc|c)ss$/,
use: [
MiniCssExtractPlugin.loader,
'css-loader',
'postcss-loader',
'sass-loader',
],
},
],
},
};
`

$3

Note: HMR is automatically supported in webpack 5. No need to configure it. Skip the following:

The mini-css-extract-plugin supports hot reloading of actual css files in development.
Some options are provided to enable HMR of both standard stylesheets and locally scoped CSS or CSS modules.
Below is an example configuration of mini-css for HMR use with CSS modules.

You should not use HotModuleReplacementPlugin plugin if you are using a webpack-dev-server.
webpack-dev-server enables / disables HMR using hot option.

webpack.config.js

`js
const webpack = require('webpack');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

const plugins = [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: devMode ? '[name].css' : '[name].[contenthash].css',
chunkFilename: devMode ? '[id].css' : '[id].[contenthash].css',
}),
];
if (devMode) {
// only enable hot in development
plugins.push(new webpack.HotModuleReplacementPlugin());
}

module.exports = {
plugins,
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: MiniCssExtractPlugin.loader,
options: {},
},
'css-loader',
],
},
],
},
};
`

$3

To minify the output, use a plugin like css-minimizer-webpack-plugin.

webpack.config.js

`js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const CssMinimizerPlugin = require('css-minimizer-webpack-plugin');

module.exports = {
plugins: [
new MiniCssExtractPlugin({
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
module: {
rules: [
{
test: /\.css$/,
use: [MiniCssExtractPlugin.loader, 'css-loader'],
},
],
},
optimization: {
minimizer: [
// For webpack@5 you can use the ... syntax to extend existing minimizers (i.e. terser-webpack-plugin), uncomment the next line
// ...,
new CssMinimizerPlugin(),
],
},
};
`

This will enable CSS optimization only in production mode. If you want to run it also in development set the optimization.minimize option to true.

$3

The runtime code detects already added CSS via or