To help you get started, we've collected the most common ways that style-loader is being used within popular public projects.

style-loader

Inject CSS into the DOM.

Getting Started

To begin, you'll need to install style-loader:

npm install --save-dev style-loader

or

yarn add -D style-loader

or

pnpm add -D style-loader

It'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
• attributes
• insert
• styleTagTransform
• base
• esModule

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 unuse is called more often than use. 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 unuse is called more often than use. 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 `` .

> ℹ️ The loader will dynamically insert the tag at runtime via JavaScript. You should use [MiniCssExtractPlugin](https://webpack.js.org/plugins/mini-css-extract-plugin/) if you want to include a static.

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:

attributes

Type:

type attributes = HTMLAttributes;

Default: {}

If defined, the style-loader will attach given attributes with their values on `

### `insert`

Type:

```ts
type insert = string;

Default: head

By default, the style-loader appends `` and works faster.

> Warning > > Do not use together style-loader and mini-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 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 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 attributes option
• using the __webpack_nonce__ variable

> Warning > > the attributes option 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.

CONTRIBUTING

License

MIT