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CompressionWebpackPlugin

Disclaimer: CompressionWebpackPlugin is a third-party package maintained by community members, it potentially does not have the same support, security policy or license as webpack, and it is not maintained by webpack.

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Prepare compressed versions of assets to serve them with Content-Encoding.

Getting Started

To begin, you'll need to install compression-webpack-plugin:

npm install compression-webpack-plugin --save-dev

or

yarn add -D compression-webpack-plugin

or

pnpm add -D compression-webpack-plugin

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

webpack.config.js

const CompressionPlugin = require("compression-webpack-plugin");

module.exports = {
  plugins: [new CompressionPlugin()],
};

Finally, run webpack using the method you normally use (e.g., via CLI or an npm script).

Options

test

Type:

type test = string | RegExp | (string | RegExp)[];

Default: undefined

Include all assets that pass test assertion.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      test: /\.js(\?.*)?$/i,
    }),
  ],
};

include

Type:

type include = string | RegExp | (string | RegExp)[];

Default: undefined

Include all assets matching any of these conditions.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      include: /\/includes/,
    }),
  ],
};

exclude

Type:

type exclude = string | RegExp | (string | RegExp)[];

Default: undefined

Exclude all assets matching any of these conditions.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      exclude: /\/excludes/,
    }),
  ],
};

algorithm

Type:

type algorithm =
  | string
  | ((
      input: Buffer,
      options: CompressionOptions,
      callback: (
        error: Error | null | undefined,
        result:
          | string
          | ArrayBuffer
          | SharedArrayBuffer
          | Uint8Array
          | readonly number[]
          | {
              valueOf(): ArrayBuffer | SharedArrayBuffer;
            }
          | {
              valueOf(): string | Uint8Array | readonly number[];
            }
          | {
              valueOf(): string;
            }
          | {
              [Symbol.toPrimitive](hint:%20%22string%22): string;
            },
      ) => void,
    ) => void);

Defines the compression algorithm or function to use. Defaults to gzip.

[!NOTE]

If you use a custom function for the algorithm option, the default value of compressionOptions will be an empty object {}.

string

The algorithm is based on the Node.js zlib module.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      algorithm: "gzip",
    }),
  ],
};

function

Allow you to specify a custom compression function.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      algorithm(input, compressionOptions, callback) {
        return compressionFunction(input, compressionOptions, callback);
      },
    }),
  ],
};

compressionOptions

Type:

interface compressionOptions {
  flush?: number;
  finishFlush?: number;
  chunkSize?: number;
  windowBits?: number;
  level?: number;
  memLevel?: number;
  strategy?: number;
  dictionary?: Buffer | TypedArray | DataView | ArrayBuffer;
  info?: boolean;
  maxOutputLength?: number;
}

Default: { level: 9 }

Compression options for algorithm.

You can find all available options in the zlib documentation.

[!NOTE]

If you use a custom function for the algorithm option, the default value of compressionOptions will be an empty object {}.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      compressionOptions: { level: 1 },
    }),
  ],
};

threshold

Type:

type threshold = number;

Default: 0

Only assets larger than this size (in bytes) are processed.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      threshold: 8192,
    }),
  ],
};

minRatio

Type:

type minRatio = number;

Default: 0.8

Only assets that compress better than this ratio are processed (minRatio = Compressed Size / Original Size). For example, if you have a image.png file with a size of 1024 bytes, and its compressed version is of 768 bytes, the minRatio is 0.75. In other words, assets will be processed only when the ratio of Compressed Size / Original Size is less than the specified minRatio.

You can use a value of 1 to process assets that are smaller than or equal to the original size.

Use a value of Infinity to process all assets, even if they are larger than the original size or their original size is 0 bytes (useful when you are pre-zipping all assets for AWS).

Use a value of Number.MAX_SAFE_INTEGER to process all assets even if they are larger than the original size, excluding assets with their original size is 0 bytes.

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      // Compress all assets, including files with `0` bytes size
      // minRatio: Infinity

      // Compress all assets, excluding files with `0` bytes size
      // minRatio: Number.MAX_SAFE_INTEGER

      minRatio: 0.8,
    }),
  ],
};

filename

Type:

type filename = string | ((pathdata: PathData) => string);

Default: "[path][base].gz"

The target asset filename.

string

For example, given an asset path: assets/images/image.png?foo=bar#hash:

[path] is replaced with the directories of the original asset, including the trailing / (assets/images/).

[file] is replaced with the path of the original asset (assets/images/image.png).

[base] is replaced with the base name ([name] + [ext]) of the original asset (image.png).

[name] is replaced with the name of the original asset (image).

[ext] is replaced with the extension of the original asset, including the . (.png).

[query] is replaced with the query of the original asset, including the ? (?foo=bar).

[fragment] is replaced with the fragment (in the concept of URL it is called hash) of the original asset (#hash).

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename: "[path][base].gz",
    }),
  ],
};

function

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename(pathData) {
        // The `pathData` argument contains all placeholders - `path`/`name`/`ext`/etc
        // Available properties described above, for the `String` notation
        if (/\.svg$/.test(pathData.filename)) {
          return "assets/svg/[path][base].gz";
        }

        return "assets/js/[path][base].gz";
      },
    }),
  ],
};

deleteOriginalAssets

Type:

type deleteOriginalAssets =
  | boolean
  | "keep-source-map"
  | ((name: string) => boolean);

Default: false

Determines whether the original (uncompressed) assets should be deleted after compression.

  • If set to true , all original assets will be deleted.

  • If set to "keep-source-map", all original assets except source maps (.map files) will be deleted.

  • If a function is provided, it will be called with each asset’s name and should return true to delete the asset or false to keep it.

Example:

module.exports = {
  plugins: [
    new CompressionPlugin({
      deleteOriginalAssets: (assetName) =>
        // Delete all assets except images
        !assetName.endsWith(".png") && !assetName.endsWith(".jpg"),
    }),
  ],
};

webpack.config.js

module.exports = {
  plugins: [
    new CompressionPlugin({
      deleteOriginalAssets: true,
    }),
  ],
};

To exclude sourcemaps from compression:

module.exports = {
  plugins: [
    new CompressionPlugin({
      exclude: /.map$/,
      deleteOriginalAssets: "keep-source-map",
    }),
  ],
};

Using a custom function:

module.exports = {
  plugins: [
    new CompressionPlugin({
      exclude: /.map$/,
      deleteOriginalAssets: (name) => {
        if (/\.js$/.test(name)) {
          return false;
        }

        return true;
      },
    }),
  ],
};

Examples

Using Zopfli

Prepare compressed versions of assets using the zopfli library.

[!NOTE]

@gfx/zopfli requires at least Node.js version 8.

To begin, you'll need to install @gfx/zopfli:

$ npm install @gfx/zopfli --save-dev

webpack.config.js

const zopfli = require("@gfx/zopfli");

module.exports = {
  plugins: [
    new CompressionPlugin({
      compressionOptions: {
        numiterations: 15,
      },
      algorithm(input, compressionOptions, callback) {
        return zopfli.gzip(input, compressionOptions, callback);
      },
    }),
  ],
};

Using Brotli

Brotli is a compression algorithm originally developed by Google, and offers compression superior to gzip.

Node.js v10.16.0 and later includes native support for Brotli compression in its zlib module.

You can take advantage of this built-in support for Brotli in Node 10.16.0 and later by just passing in the appropriate algorithm to the CompressionPlugin:

webpack.config.js

const zlib = require("node:zlib");

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename: "[path][base].br",
      algorithm: "brotliCompress",
      test: /\.(js|css|html|svg)$/,
      compressionOptions: {
        params: {
          [zlib.constants.BROTLI_PARAM_QUALITY]: 11,
        },
      },
      threshold: 10240,
      minRatio: 0.8,
      deleteOriginalAssets: false,
    }),
  ],
};

[!NOTE] Brotli’s BROTLI_PARAM_QUALITY option is functionally equivalent to zlib’s level option. You can find all Brotli’s options in the relevant part of the zlib module documentation.

Using Zstandard

Zstandard (zstd) is a fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level and better compression ratios.

Node.js 22.15.0 and later includes native support for Zstandard compression in its zlib module.

You can take advantage of this built-in support for zstd in Node 22.15.0 and later by just passing in the appropriate algorithm to the CompressionPlugin:

webpack.config.js

const zlib = require("node:zlib");

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename: "[path][base].zst",
      algorithm: "zstdCompress",
      test: /\.(js|css|html|svg)$/,
      compressionOptions: {
        params: {
          [zlib.constants.ZSTD_c_compressionLevel]: 10,
        },
      },
      threshold: 10240,
      minRatio: 0.8,
      deleteOriginalAssets: false,
    }),
  ],
};

You can find all Zstandard's options in the relevant part of the zlib module documentation.

Multiple compressed versions of assets for different algorithm

webpack.config.js

const zlib = require("node:zlib");

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename: "[path][base].gz",
      algorithm: "gzip",
      test: /\.js$|\.css$|\.html$/,
      threshold: 10240,
      minRatio: 0.8,
    }),
    new CompressionPlugin({
      filename: "[path][base].br",
      algorithm: "brotliCompress",
      test: /\.(js|css|html|svg)$/,
      compressionOptions: {
        params: {
          [zlib.constants.BROTLI_PARAM_QUALITY]: 11,
        },
      },
      threshold: 10240,
      minRatio: 0.8,
    }),
  ],
};

Contributing

We welcome contributions!

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

CONTRIBUTING

License

MIT

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