webpack-contrib
Style Loader
style-loader
Inject CSS into the DOM.
Getting Started
To begin, you'll need to install style-loader:
npm install --save-dev style-loaderor
yarn add -D style-loaderor
pnpm add -D style-loaderIt's recommended to combine style-loader with the css-loader
Then add the loader to your webpack config. For example:
style.css
body {
background: green;
}component.js
import "./style.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
};Security Warning
This loader is primarily meant for development. The default settings are not safe for production environments. See the recommended example configuration and the section on nonces for details.
Options
injectType
Type:
type injectType =
| "styleTag"
| "singletonStyleTag"
| "autoStyleTag"
| "lazyStyleTag"
| "lazySingletonStyleTag"
| "lazyAutoStyleTag"
| "linkTag";Default: styleTag
Allows to setup how styles will be injected into the DOM.
Possible values:
styleTag
Automatically injects styles into the DOM using multiple <style></style>. It is default behaviour.
component.js
import "./styles.css";Example with Locals (CSS Modules):
component-with-css-modules.js
import * as styles from "./styles.css";
const divElement = document.createElement("div");
divElement.className = styles["my-class"];All local variables (class names) are exported as named exports. To achieve this behaviour you also have to setup modules option for css-loader. For more information consult with css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
// The `injectType` option can be avoided because it is default behaviour
{ loader: "style-loader", options: { injectType: "styleTag" } },
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader inject styles like:
<style>
.foo {
color: red;
}
</style>
<style>
.bar {
color: blue;
}
</style>singletonStyleTag
Automatically injects styles into the DOM using one <style></style>.
Warning
Source maps do not work.
component.js
import "./styles.css";component-with-css-modules.js
import * as styles from "./styles.css";
const divElement = document.createElement("div");
divElement.className = styles["my-class"];All local variables (class names) are exported as named exports. To achieve this behaviour you also have to setup modules option for css-loader. For more information consult with css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: { injectType: "singletonStyleTag" },
},
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader inject styles like:
<style>
.foo {
color: red;
}
.bar {
color: blue;
}
</style>autoStyleTag
Works the same as a styleTag, but if the code is executed in IE6-9, turns on the singletonStyleTag mode.
lazyStyleTag
Injects styles into the DOM using multiple <style></style> on demand.
We recommend following .lazy.css naming convention for lazy styles and the .css for basic style-loader usage (similar to other file types, i.e. .lazy.less and .less).
When you lazyStyleTag value the style-loader injects the styles lazily making them useable on-demand via style.use() / style.unuse().
⚠️ Behavior is undefined when
unuseis called more often thanuse. Don't do that.
component.js
import styles from "./styles.lazy.css";
styles.use();
// For removing styles you can use
// styles.unuse();component-with-css-modules.js
import styles, { "my-class" as myClass } from "./styles.lazy.css";
styles.use();
const divElement = document.createElement("div");
divElement.className = myClass;All local variables (class names) are exported as named exports. To achieve this behaviour you also have to setup modules option for css-loader. For more information consult with css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
exclude: /\.lazy\.css$/i,
use: ["style-loader", "css-loader"],
},
{
test: /\.lazy\.css$/i,
use: [
{ loader: "style-loader", options: { injectType: "lazyStyleTag" } },
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader inject styles like:
<style>
.foo {
color: red;
}
</style>
<style>
.bar {
color: blue;
}
</style>lazySingletonStyleTag
Injects styles into the DOM using one <style></style> on demand.
We recommend following .lazy.css naming convention for lazy styles and the .css for basic style-loader usage (similar to other file types, i.e. .lazy.less and .less).
When you lazySingletonStyleTag value the style-loader injects the styles lazily making them useable on-demand via style.use() / style.unuse().
⚠️ Source maps do not work.
⚠️ Behavior is undefined when
unuseis called more often thanuse. Don't do that.
component.js
import styles from "./styles.css";
styles.use();
// For removing styles you can use
// styles.unuse();component-with-css-modules.js
import styles, { "my-class" as myClass } from "./styles.lazy.css";
styles.use();
const divElement = document.createElement("div");
divElement.className = myClass;All local variables (class names) are exported as named exports. To achieve this behaviour you also have to setup modules option for css-loader. For more information consult with css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
exclude: /\.lazy\.css$/i,
use: ["style-loader", "css-loader"],
},
{
test: /\.lazy\.css$/i,
use: [
{
loader: "style-loader",
options: { injectType: "lazySingletonStyleTag" },
},
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader generate this:
<style>
.foo {
color: red;
}
.bar {
color: blue;
}
</style>lazyAutoStyleTag
Works the same as a lazyStyleTag, but if the code is executed in IE6-9, turns on the lazySingletonStyleTag mode.
linkTag
Injects styles into the DOM using multiple <link rel="stylesheet" href="path/to/file.css"> .
ℹ️ The loader will dynamically insert the
<link href="path/to/file.css" rel="stylesheet">tag at runtime via JavaScript. You should use MiniCssExtractPlugin if you want to include a static<link href="path/to/file.css" rel="stylesheet">.
import "./styles.css";
import "./other-styles.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.link\.css$/i,
use: [
{ loader: "style-loader", options: { injectType: "linkTag" } },
{ loader: "file-loader" },
],
},
],
},
};The loader generate this:
<link rel="stylesheet" href="path/to/style.css" />
<link rel="stylesheet" href="path/to/other-styles.css" />attributes
Type:
type attributes = HTMLAttributes;Default: {}
If defined, the style-loader will attach given attributes with their values on <style> / <link> element.
component.js
import "./file.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader", options: { attributes: { id: "id" } } },
{ loader: "css-loader" },
],
},
],
},
};<style id="id"></style>insert
Type:
type insert = string;Default: head
By default, the style-loader appends <style>/<link> elements to the end of the style target, which is the <head> tag of the page unless specified by insert.
This will cause CSS created by the loader to take priority over CSS already present in the target.
You can use other values if the standard behavior is not suitable for you, but we do not recommend doing this.
If you target an iframe make sure you have sufficient access rights, the styles will be injected into the content document head.
Selector
Allows to setup custom query selector where styles inject into the DOM.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: "body",
},
},
"css-loader",
],
},
],
},
};Absolute path to function
Allows to setup absolute path to custom function that allows to override default behavior and insert styles at any position.
Warning
Do not forget that this code will be used in the browser and not all browsers support latest ECMA features like
let,const,arrow function expressionand etc. We recommend usingbabel-loaderfor support latest ECMA features.
Warning
Do not forget that some DOM methods may not be available in older browsers, we recommended use only DOM core level 2 properties, but it is depends what browsers you want to support
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./path-to-insert-module"),
},
},
"css-loader",
],
},
],
},
};A new <style>/<link> elements will be inserted into at bottom of body tag.
Examples:
Insert styles at top of head tag:
insert-function.js
function insertAtTop(element) {
var parent = document.querySelector("head");
// eslint-disable-next-line no-underscore-dangle
var lastInsertedElement = window._lastElementInsertedByStyleLoader;
if (!lastInsertedElement) {
parent.insertBefore(element, parent.firstChild);
} else if (lastInsertedElement.nextSibling) {
parent.insertBefore(element, lastInsertedElement.nextSibling);
} else {
parent.appendChild(element);
}
// eslint-disable-next-line no-underscore-dangle
window._lastElementInsertedByStyleLoader = element;
}
module.exports = insertAtTop;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./insert-function"),
},
},
"css-loader",
],
},
],
},
};You can pass any parameters to style.use(options) and this value will be passed to insert and styleTagTransform functions.
insert-function.js
function insertIntoTarget(element, options) {
var parent = options.target || document.head;
parent.appendChild(element);
}
module.exports = insertIntoTarget;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
injectType: "lazyStyleTag",
// Do not forget that this code will be used in the browser and
// not all browsers support latest ECMA features like `let`, `const`, `arrow function expression` and etc,
// we recommend use only ECMA 5 features,
// but it depends what browsers you want to support
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};Insert styles to the provided element or to the head tag if target isn't provided. Now you can inject styles into Shadow DOM (or any other element).
custom-square.css
div {
width: 50px;
height: 50px;
background-color: red;
}custom-square.js
import customSquareStyles from "./custom-square.css";
class CustomSquare extends HTMLElement {
constructor() {
super();
this.attachShadow({ mode: "open" });
const divElement = document.createElement("div");
divElement.textContent = "Text content.";
this.shadowRoot.appendChild(divElement);
customSquareStyles.use({ target: this.shadowRoot });
// You can override injected styles
const bgPurple = new CSSStyleSheet();
const width = this.getAttribute("w");
const height = this.getAttribute("h");
bgPurple.replace(`div { width: ${width}px; height: ${height}px; }`);
this.shadowRoot.adoptedStyleSheets = [bgPurple];
// `divElement` will have `100px` width, `100px` height and `red` background color
}
}
customElements.define("custom-square", CustomSquare);
export default CustomSquare;styleTagTransform
Type:
type styleTagTransform = string;Default: undefined
string
Allows to setup absolute path to custom function that allows to override default behavior styleTagTransform.
Warning
Do not forget that this code will be used in the browser and not all browsers support latest ECMA features like
let,const,arrow function expressionand etc, we recommend use only ECMA 5 features, but it is depends what browsers you want to support
Warning
Do not forget that some DOM methods may not be available in older browsers, we recommended use only DOM core level 2 properties, but it depends what browsers you want to support
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
injectType: "styleTag",
styleTagTransform: require.resolve("style-tag-transform-code"),
},
},
"css-loader",
],
},
],
},
};base
type base = number;This setting is primarily used as a workaround for css clashes when using one or more DllPlugin's. base allows you to prevent either the app's css (or DllPlugin2's css) from overwriting DllPlugin1's css by specifying a css module id base which is greater than the range used by DllPlugin1 e.g.:
webpack.dll1.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
};webpack.dll2.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader", options: { base: 1000 } },
"css-loader",
],
},
],
},
};webpack.app.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader", options: { base: 2000 } },
"css-loader",
],
},
],
},
};esModule
Type:
type esModule = boolean;Default: true
By default, style-loader generates JS modules that use the ES modules syntax.
There are some cases in which using ES modules is beneficial, like in the case of module concatenation and tree shaking.
You can enable a CommonJS modules syntax using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "style-loader",
options: {
esModule: false,
},
},
],
},
};Examples
Recommend
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 <style></style> and works faster.
Warning
Do not use together
style-loaderandmini-css-extract-plugin.
webpack.config.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const devMode = process.env.NODE_ENV !== "production";
module.exports = {
module: {
rules: [
{
test: /\.(sa|sc|c)ss$/,
use: [
devMode ? "style-loader" : MiniCssExtractPlugin.loader,
"css-loader",
"postcss-loader",
"sass-loader",
],
},
],
},
plugins: [].concat(devMode ? [] : [new MiniCssExtractPlugin()]),
};Named export for CSS Modules
Warning
It is not allowed to use JavaScript reserved words in css class names.
Warning
Options
esModuleandmodules.namedExportincss-loadershould be enabled (by default forcss-loader@7it is true).
styles.css
.fooBaz {
color: red;
}
.bar {
color: blue;
}
.my-class {
color: green;
}index.js
import { fooBaz, bar, "my-class" as myClass } from "./styles.css";
console.log(fooBaz, bar, myClass);Or:
index.js
import * as styles from "./styles.css";
console.log(styles.fooBaz, styles.bar, styles["my-class"]);You can enable a ES module named export using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: "style-loader",
},
{
loader: "css-loader",
options: {
modules: {
namedExport: true,
},
},
},
],
},
],
},
};Source maps
The loader automatically inject source maps when previous loader emit them.
Therefore, to generate source maps, set the sourceMap option to true for the previous loader.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{ loader: "css-loader", options: { sourceMap: true } },
],
},
],
},
};Nonce
If you are using a Content Security Policy (CSP), the injected code will usually be blocked. A workaround is to use a nonce. Note, however, that using a nonce significantly reduces the protection provided by the CSP. You can read more about the security impact in the specification. The better solution is not to use this loader in production.
There are two ways to work with nonce:
- using the
attributesoption - using the
__webpack_nonce__variable
Warning
the
attributesoption takes precedence over the__webpack_nonce__variable
attributes
component.js
import "./style.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
attributes: {
nonce: "12345678",
},
},
},
"css-loader",
],
},
],
},
};The loader generate:
<style nonce="12345678">
.foo {
color: red;
}
</style>__webpack_nonce__
create-nonce.js
__webpack_nonce__ = "12345678";component.js
import "./create-nonce.js";
import "./style.css";Alternative example for require:
component.js
__webpack_nonce__ = "12345678";
require("./style.css");webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
};The loader generate:
<style nonce="12345678">
.foo {
color: red;
}
</style>Insert styles at top
Insert styles at top of head tag.
insert-function.js
function insertAtTop(element) {
var parent = document.querySelector("head");
var lastInsertedElement = window._lastElementInsertedByStyleLoader;
if (!lastInsertedElement) {
parent.insertBefore(element, parent.firstChild);
} else if (lastInsertedElement.nextSibling) {
parent.insertBefore(element, lastInsertedElement.nextSibling);
} else {
parent.appendChild(element);
}
window._lastElementInsertedByStyleLoader = element;
}
module.exports = insertAtTop;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};Insert styles before target element
Inserts styles before #id element.
insert-function.js
function insertBeforeAt(element) {
const parent = document.querySelector("head");
const target = document.querySelector("#id");
const lastInsertedElement = window._lastElementInsertedByStyleLoader;
if (!lastInsertedElement) {
parent.insertBefore(element, target);
} else if (lastInsertedElement.nextSibling) {
parent.insertBefore(element, lastInsertedElement.nextSibling);
} else {
parent.appendChild(element);
}
window._lastElementInsertedByStyleLoader = element;
}
module.exports = insertBeforeAt;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};Custom Elements (Shadow DOM)
You can define custom target for your styles for the lazyStyleTag type.
insert-function.js
function insertIntoTarget(element, options) {
var parent = options.target || document.head;
parent.appendChild(element);
}
module.exports = insertIntoTarget;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
injectType: "lazyStyleTag",
// Do not forget that this code will be used in the browser and
// not all browsers support latest ECMA features like `let`, `const`, `arrow function expression` and etc,
// we recommend use only ECMA 5 features,
// but it is depends what browsers you want to support
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};Insert styles to the provided element or to the head tag if target isn't provided.
custom-square.css
div {
width: 50px;
height: 50px;
background-color: red;
}custom-square.js
import customSquareStyles from "./custom-square.css";
class CustomSquare extends HTMLElement {
constructor() {
super();
this.attachShadow({ mode: "open" });
const divElement = document.createElement("div");
divElement.textContent = "Text content.";
this.shadowRoot.appendChild(divElement);
customSquareStyles.use({ target: this.shadowRoot });
// You can override injected styles
const bgPurple = new CSSStyleSheet();
const width = this.getAttribute("w");
const height = this.getAttribute("h");
bgPurple.replace(`div { width: ${width}px; height: ${height}px; }`);
this.shadowRoot.adoptedStyleSheets = [bgPurple];
// `divElement` will have `100px` width, `100px` height and `red` background color
}
}
customElements.define("custom-square", CustomSquare);
export default CustomSquare;Contributing
Please take a moment to read our contributing guidelines if you haven't yet done so.