css-minimizer-webpack-plugin/README.md

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# css-minimizer-webpack-plugin

This plugin uses [cssnano](https://cssnano.co) to optimize and minify your CSS.

Just like [optimize-css-assets-webpack-plugin](https://github.com/NMFR/optimize-css-assets-webpack-plugin) but more accurate with source maps and assets using query string, allows caching and works in parallel mode.

## Getting Started

To begin, you'll need to install `css-minimizer-webpack-plugin`:

```console
$ npm install css-minimizer-webpack-plugin --save-dev
```

Then add the plugin to your `webpack` configuration. For example:

**webpack.config.js**

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

module.exports = {
  module: {
    rules: [
      {
        test: /.s?css$/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "sass-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(),
    ],
  },
  plugins: [new MiniCssExtractPlugin()],
};
```

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`:

**webpack.config.js**

```js
// [...]
module.exports = {
  optimization: {
    // [...]
    minimize: true,
  },
};
```

And run `webpack` via your preferred method.

## Note about source maps

**Works only with `source-map`, `inline-source-map`, `hidden-source-map` and `nosources-source-map` values for the [`devtool`](https://webpack.js.org/configuration/devtool/) option.**

Why? Because CSS support only these source map types.

The plugin respect the [`devtool`](https://webpack.js.org/configuration/devtool/) and using the `SourceMapDevToolPlugin` plugin.
Using supported `devtool` values enable source map generation.
Using `SourceMapDevToolPlugin` with enabled the `columns` option enables source map generation.

Use source maps to map error message locations to modules (this slows down the compilation).
If you use your own `minify` function please read the `minify` section for handling source maps correctly.

## Options

|                    Name                     |                      Type                      |              Default               | Description                                                             |
| :-----------------------------------------: | :--------------------------------------------: | :--------------------------------: | :---------------------------------------------------------------------- |
|             **[`test`](#test)**             |    `String\|RegExp\|Array<String\|RegExp>`     |         `/\.css(\?.*)?$/i`         | Test to match files against.                                            |
|          **[`include`](#include)**          |    `String\|RegExp\|Array<String\|RegExp>`     |            `undefined`             | Files to include.                                                       |
|          **[`exclude`](#exclude)**          |    `String\|RegExp\|Array<String\|RegExp>`     |            `undefined`             | Files to exclude.                                                       |
|         **[`parallel`](#parallel)**         |               `Boolean\|Number`                |               `true`               | Enable/disable multi-process parallel running.                          |
|           **[`minify`](#minify)**           |          `Function\|Array<Function>`           | `CssMinimizerPlugin.cssnanoMinify` | Allows to override default minify function.                             |
| **[`minimizerOptions`](#minimizeroptions)** |            `Object\|Array<Object>`             |      `{ preset: 'default' }`       | Cssnano optimisations [options](https://cssnano.co/docs/optimisations). |
|   **[`warningsFilter`](#warningsfilter)**   | `Function<(warning, file, source) -> Boolean>` |            `() => true`            | Allow to filter css-minimizer warnings.                                 |

### `test`

Type: `String|RegExp|Array<String|RegExp>` - default: `/\.css(\?.*)?$/i`

Test to match files against.

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        test: /\.foo\.css$/i,
      }),
    ],
  },
};
```

### `include`

Type: `String|RegExp|Array<String|RegExp>`
Default: `undefined`

Files to include.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        include: /\/includes/,
      }),
    ],
  },
};
```

### `exclude`

Type: `String|RegExp|Array<String|RegExp>`
Default: `undefined`

Files to exclude.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        exclude: /\/excludes/,
      }),
    ],
  },
};
```

### `parallel`

Type: `Boolean|Number`
Default: `true`

Use multi-process parallel running to improve the build speed.
Default number of concurrent runs: `os.cpus().length - 1`.

> ℹ️ Parallelization can speed up your build significantly and is therefore **highly recommended**.
> If a parallelization is enabled, the packages in `minimizerOptions` must be required via strings (`packageName` or `require.resolve(packageName)`). Read more in [`minimizerOptions`](#minimizeroptions)

#### `Boolean`

Enable/disable multi-process parallel running.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: true,
      }),
    ],
  },
};
```

#### `Number`

Enable multi-process parallel running and set number of concurrent runs.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: 4,
      }),
    ],
  },
};
```

### `minify`

Type: `Function|Array<Function>`
Default: `CssMinimizerPlugin.cssnanoMinify`

Allows overriding default minify function.
By default, plugin uses [cssnano](https://github.com/cssnano/cssnano) package.
Useful for using and testing unpublished versions or forks.

Possible options:

- CssMinimizerPlugin.cssnanoMinify
- CssMinimizerPlugin.cssoMinify
- CssMinimizerPlugin.cleanCssMinify
- CssMinimizerPlugin.esbuildMinify
- CssMinimizerPlugin.parcelCssMinify
- `async (data, inputMap, minimizerOptions) => {return {code: "a{color: red}", map: "...", warnings: [], errors: []}}`

> ⚠️ **Always use `require` inside `minify` function when `parallel` option enabled**.

#### `Function`

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          level: {
            1: {
              roundingPrecision: "all=3,px=5",
            },
          },
        },
        minify: CssMinimizerPlugin.cleanCssMinify,
      }),
    ],
  },
};
```

#### `Array`

If an array of functions is passed to the `minify` option, the `minimizerOptions` must also be an array.
The function index in the `minify` array corresponds to the options object with the same index in the `minimizerOptions` array.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: [
          {}, // Options for the first function (CssMinimizerPlugin.cssnanoMinify)
          {}, // Options for the second function (CssMinimizerPlugin.cleanCssMinify)
          {}, // Options for the third function
        ],
        minify: [
          CssMinimizerPlugin.cssnanoMinify,
          CssMinimizerPlugin.cleanCssMinify,
          async (data, inputMap, minimizerOptions) => {
            // To do something
            return {
              code: `a{color: red}`,
              map: `{"version": "3", ...}`,
              warnings: [],
              errors: [],
            };
          },
        ],
      }),
    ],
  },
};
```

### `minimizerOptions`

Type: `Object|Array<Object>`
Default: `{ preset: 'default' }`

Cssnano optimisations [options](https://cssnano.co/docs/optimisations).

#### `Object`

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: [
            "default",
            {
              discardComments: { removeAll: true },
            },
          ],
        },
      }),
    ],
  },
};
```

#### `Array`

The function index in the `minify` array corresponds to the options object with the same index in the `minimizerOptions` array.
If you use `minimizerOptions` like object, all `minify` function accept it.

> If a parallelization is enabled, the packages in `minimizerOptions` must be required via strings (`packageName` or `require.resolve(packageName)`). In this case, we shouldn't use `require`/`import`.

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: require.resolve("cssnano-preset-simple"),
        },
      }),
    ],
  },
};
```

##### `processorOptions` (⚠ only cssnano)

Type: `Object`
Default: `{ from: assetName }`

Allows filtering options [`processoptions`](https://postcss.org/api/#processoptions) for the cssnano.
The `parser`,` stringifier` and `syntax` can be either a function or a string indicating the module that will be imported.

> ⚠️ **If a function is passed, the `parallel` option must be disabled.**.

```js
import sugarss from "sugarss";

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: false,
        minimizerOptions: {
          processorOptions: {
            parser: sugarss,
          },
        },
      }),
    ],
  },
};
```

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          processorOptions: {
            parser: "sugarss",
          },
        },
      }),
    ],
  },
};
```

### `warningsFilter`

Type: `Function<(warning, file, source) -> Boolean>`
Default: `() => true`

Allow filtering css-minimizer warnings (By default [cssnano](https://github.com/cssnano/cssnano)).
Return `true` to keep the warning, a falsy value (`false`/`null`/`undefined`) otherwise.

> ⚠️ The `source` argument will contain `undefined` if you don't use source maps.

**webpack.config.js**

```js
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        warningsFilter: (warning, file, source) => {
          if (/Dropping unreachable code/i.test(warning)) {
            return true;
          }

          if (/file\.css/i.test(file)) {
            return true;
          }

          if (/source\.css/i.test(source)) {
            return true;
          }

          return false;
        },
      }),
    ],
  },
};
```

## Examples

### Use sourcemaps

Don't forget to enable `sourceMap` options for all loaders.

```js
const CssMinimizerPlugin = require("css-minimizer-webpack-plugin");

module.exports = {
  devtool: "source-map",
  module: {
    rules: [
      {
        test: /.s?css$/,
        use: [
          MiniCssExtractPlugin.loader,
          { loader: "css-loader", options: { sourceMap: true } },
          { loader: "sass-loader", options: { sourceMap: true } },
        ],
      },
    ],
  },
  optimization: {
    minimizer: [new CssMinimizerPlugin()],
  },
  plugins: [new MiniCssExtractPlugin()],
};
```

### Remove all comments

Remove all comments (including comments starting with `/*!`).

```js
module.exports = {
  optimization: {
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: [
            "default",
            {
              discardComments: { removeAll: true },
            },
          ],
        },
      }),
    ],
  },
};
```

### Using custom minifier [csso](https://github.com/css/csso)

**webpack.config.js**

```js
module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.cssoMinify,
        // Uncomment this line for options
        // minimizerOptions: { restructure: false },
      }),
    ],
  },
};
```

### Using custom minifier [clean-css](https://github.com/jakubpawlowicz/clean-css)

**webpack.config.js**

```js
module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.cleanCssMinify,
        // Uncomment this line for options
        // minimizerOptions: { compatibility: 'ie11,-properties.merging' },
      }),
    ],
  },
};
```

### Using custom minifier [esbuild](https://github.com/evanw/esbuild)

**webpack.config.js**

```js
module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.esbuildMinify,
      }),
    ],
  },
};
```

### Using custom minifier [@parcel/css](https://github.com/parcel-bundler/parcel-css)

**webpack.config.js**

```js
module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.parcelCssMinify,
        // Uncomment this line for options
        // minimizerOptions: { targets: { ie: 11 }, drafts: { nesting: true } },
      }),
    ],
  },
};
```

## Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

[CONTRIBUTING](./.github/CONTRIBUTING.md)

## License

[MIT](./LICENSE)

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