Inject CSS into the DOM.
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 configuration. For example:
style.css
body {
background: green;
}component.js
import "./style.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
};This loader is primarily meant for development. The default settings are not safe for production environments. See the recommended example configuration and the section on nonces for details.
Type:
type injectType =
| "styleTag"
| "singletonStyleTag"
| "autoStyleTag"
| "lazyStyleTag"
| "lazySingletonStyleTag"
| "lazyAutoStyleTag"
| "linkTag";Default: styleTag
Allows you to setup how styles will be injected into the DOM.
Possible values:
Automatically injects styles into the DOM using multiple <style></style>. It is the default behaviour.
component.js
import "./styles.css";Example with Locals (CSS Modules):
component-with-css-modules.js
import * as styles from "./styles.css";
const divElement = document.createElement("div");
divElement.className = styles["my-class"];All local variables (class names) are exported as named exports. To achieve this behaviour you also have to set up the modules option for css-loader. For more information, consult the css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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>Automatically injects styles into the DOM using a single <style></style> tag.
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 set up the modules option for css-loader. For more information, consult the css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: { injectType: "singletonStyleTag" },
},
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader inject styles like:
<style>
.foo {
color: red;
}
.bar {
color: blue;
}
</style>Works the same as a styleTag, but if the code is executed in IE6-9, turns on the singletonStyleTag mode.
Injects styles into the DOM using multiple <style></style> tags on demand.
We recommend following the .lazy.css naming convention for lazy styles and .css for basic style-loader usage (similar to other file types, i.e. .lazy.less and .less).
When you use the lazyStyleTag value, style-loader injects the styles lazily, making them useable on-demand via style.use() / style.unuse().
⚠️ Behavior is undefined whenunuseis called more often thanuse. Don't do that.
component.js
import styles from "./styles.lazy.css";
styles.use();
// For removing styles you can use
// styles.unuse();component-with-css-modules.js
import styles, { "my-class" as myClass } from "./styles.lazy.css";
styles.use();
const divElement = document.createElement("div");
divElement.className = myClass;All local variables (class names) are exported as named exports. To achieve this behaviour, you also have to set up the modules option for css-loader. For more information, consult the css-loader documentation.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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>Injects styles into the DOM using a single <style></style> tag 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 use the lazySingletonStyleTag value, style-loader injects the styles lazily making them useable on-demand via style.use() / style.unuse().
⚠️ Source maps do not work.
⚠️ Behavior is undefined whenunuseis 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 set up the modules option for css-loader. For more information, consult the 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$/i,
use: [
{
loader: "style-loader",
options: { injectType: "lazySingletonStyleTag" },
},
{
loader: "css-loader",
// Uncomment it if you want to use CSS modules
// options: { modules: true }
},
],
},
],
},
};The loader generate this:
<style>
.foo {
color: red;
}
.bar {
color: blue;
}
</style>Works the same as a lazyStyleTag, but if the code is executed in IE6-9, turns on the lazySingletonStyleTag mode.
Injects styles into the DOM using multiple <link rel="stylesheet" href="path/to/file.css"> .
ℹ️ The loader will dynamically insert the
<link href="path/to/file.css" rel="stylesheet">tag at runtime via JavaScript. You should use MiniCssExtractPlugin if you want to include a static<link href="path/to/file.css" rel="stylesheet">.
import "./styles.css";
import "./other-styles.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.link\.css$/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" />Type:
type attributes = HTMLAttributes;Default: {}
If defined, the style-loader will attach the given attributes with their values on <style> / <link> element.
component.js
import "./file.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader", options: { attributes: { id: "id" } } },
{ loader: "css-loader" },
],
},
],
},
};<style id="id"></style>Type:
type insert = string;Default: head
By default, the style-loader appends <style>/<link> elements to the end of the style target, which is the <head> tag of the page unless specified by insert.
This will cause CSS created by the loader to take priority over CSS already present in the target.
You can use other values if the standard behavior is not suitable for you, but we do not recommend doing this.
If you target an iframe, make sure you have sufficient access rights; the styles will be injected into the content document head.
Allows you to setup custom query selector where styles are injected into the DOM.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: "body",
},
},
"css-loader",
],
},
],
},
};Allows you to setup an absolute path to custom function that allows to override the 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 expression, etc. We recommend using babel-loader to support the latest ECMA features.
Warning
Do not forget that some DOM methods may not be available in older browsers. We recommended using only DOM core level 2 properties, but it depends on which browsers you want to support.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./path-to-insert-module"),
},
},
"css-loader",
],
},
],
},
};New <style>/<link> elements will be inserted at the bottom of the body tag.
Examples:
Insert styles at top of head tag:
insert-function.js
function insertAtTop(element) {
var parent = document.querySelector("head");
// eslint-disable-next-line no-underscore-dangle
var lastInsertedElement = window._lastElementInsertedByStyleLoader;
if (!lastInsertedElement) {
parent.insertBefore(element, parent.firstChild);
} else if (lastInsertedElement.nextSibling) {
parent.insertBefore(element, lastInsertedElement.nextSibling);
} else {
parent.appendChild(element);
}
// eslint-disable-next-line no-underscore-dangle
window._lastElementInsertedByStyleLoader = element;
}
module.exports = insertAtTop;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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 the 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: ${height}px; }`);
this.shadowRoot.adoptedStyleSheets = [bgPurple];
// `divElement` will have `100px` width, `100px` height and `red` background color
}
}
customElements.define("custom-square", CustomSquare);
export default CustomSquare;Type:
type styleTagTransform = string;Default: undefined
Allows you to setup an absolute path to a custom function that allows to override default styleTagTransform behavior.
Warning
Do not forget that this code will be used in the browser and not all browsers support latest ECMA features like let, const, arrow function expression, etc. We recommend use only ECMA 5 features, but it depends on which browsers you want to support.
Warning
Do not forget that some DOM methods may not be available in older browsers. We recommended using only DOM core level 2 properties, but it depends on which browsers you want to support.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
injectType: "styleTag",
styleTagTransform: require.resolve("style-tag-transform-code"),
},
},
"css-loader",
],
},
],
},
};type base = number;This setting is primarily used as a workaround for CSS clashes when using one or more DllPlugins.
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 that 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$/i,
use: [
{ loader: "style-loader", options: { base: 2000 } },
"css-loader",
],
},
],
},
};Type:
type esModule = boolean;Default: true
By default, style-loader generates JS modules that use the ES modules syntax.
There are some cases in which using ES modules is beneficial, such as in the case of module concatenation and tree shaking.
You can enable a CommonJS module syntax using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "style-loader",
options: {
esModule: false,
},
},
],
},
};For production builds, it's recommended to extract the CSS from your bundle to enable 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> tags and works faster.
Warning
Do not use style-loader and mini-css-extract-plugin together.
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$/,
use: [
devMode ? "style-loader" : MiniCssExtractPlugin.loader,
"css-loader",
"postcss-loader",
"sass-loader",
],
},
],
},
plugins: [].concat(devMode ? [] : [new MiniCssExtractPlugin()]),
};Warning
It is not allowed to use JavaScript reserved words in CSS class names.
Warning
Options esModule and modules.namedExport in css-loader should be enabled (by default for css-loader@7 it is true).
styles.css
.fooBaz {
color: red;
}
.bar {
color: blue;
}
.my-class {
color: green;
}index.js
import { fooBaz, bar, "my-class" as myClass } from "./styles.css";
console.log(fooBaz, bar, myClass);Or:
index.js
import * as styles from "./styles.css";
console.log(styles.fooBaz, styles.bar, styles["my-class"]);You can enable an ES module named export using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
{
loader: "style-loader",
},
{
loader: "css-loader",
options: {
modules: {
namedExport: true,
},
},
},
],
},
],
},
};The loader automatically injects source maps when the previous loader emits 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$/i,
use: [
"style-loader",
{ loader: "css-loader", options: { sourceMap: true } },
],
},
],
},
};If you are using a Content Security Policy (CSP), the injected code will usually be blocked. A workaround is to use a nonce. Note, however, that using a nonce significantly reduces the protection provided by the CSP. You can read more about the security impact in the specification. The better solution is not to use this loader in production.
There are two ways to work with nonce:
- Using the
attributesoption - Using the
__webpack_nonce__variable
Warning
the attributes option takes precedence over the __webpack_nonce__ variable
component.js
import "./style.css";webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
attributes: {
nonce: "12345678",
},
},
},
"css-loader",
],
},
],
},
};The loader generate:
<style nonce="12345678">
.foo {
color: red;
}
</style>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$/i,
use: ["style-loader", "css-loader"],
},
],
},
};The loader generate:
<style nonce="12345678">
.foo {
color: red;
}
</style>Insert styles at top of head tag.
insert-function.js
function insertAtTop(element) {
var parent = document.querySelector("head");
var lastInsertedElement = window._lastElementInsertedByStyleLoader;
if (!lastInsertedElement) {
parent.insertBefore(element, parent.firstChild);
} else if (lastInsertedElement.nextSibling) {
parent.insertBefore(element, lastInsertedElement.nextSibling);
} else {
parent.appendChild(element);
}
window._lastElementInsertedByStyleLoader = element;
}
module.exports = insertAtTop;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};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$/i,
use: [
{
loader: "style-loader",
options: {
insert: require.resolve("./insert-function.js"),
},
},
"css-loader",
],
},
],
},
};You can define custom target for your styles when using the lazyStyleTag type.
insert-function.js
function insertIntoTarget(element, options) {
var parent = options.target || document.head;
parent.appendChild(element);
}
module.exports = insertIntoTarget;webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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 into the head tag if the 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;We welcome all contributions! If you're new here, please take a moment to review our contributing guidelines before submitting issues or pull requests.
