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Plugins are the backbone of webpack’s functionality. They can perform a wide range of tasks like bundle optimization, asset management, and environment variable injection.

​
Basic Configuration

webpack.config.js
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html'
    })
  ]
};

​
Plugins Array

​
plugins
array
Add additional plugins to the compiler.
plugins: [
  new Plugin1(),
  new Plugin2(options),
  // Conditional plugin
  isDevelopment && new DevPlugin()
].filter(Boolean)
Plugins are instantiated with the new operator and can receive configuration options.

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Built-in Plugins

Webpack includes several built-in plugins accessible via webpack module:

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DefinePlugin

Create global constants available at compile time: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify('production'),
      'process.env.API_URL': JSON.stringify('https://api.example.com'),
      VERSION: JSON.stringify('1.0.0'),
      PRODUCTION: true,
      __DEV__: false
    })
  ]
};

​
ProvidePlugin

Automatically load modules instead of importing/requiring them: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.ProvidePlugin({
      $: 'jquery',
      jQuery: 'jquery',
      'window.jQuery': 'jquery',
      process: 'process/browser'
    })
  ]
};

​
BannerPlugin

Add a banner to the top of generated chunks: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.BannerPlugin({
      banner: '/*! Copyright 2024 MyCompany */',
      raw: true,
      entryOnly: true
    })
  ]
};

​
EnvironmentPlugin

Shorthand for DefinePlugin on process.env keys: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.EnvironmentPlugin(['NODE_ENV', 'API_URL'])
    // or with defaults
    new webpack.EnvironmentPlugin({
      NODE_ENV: 'development',
      DEBUG: false
    })
  ]
};

​
IgnorePlugin

Exclude certain modules from bundles: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.IgnorePlugin({
      resourceRegExp: /^\.\/locale$/,
      contextRegExp: /moment$/
    })
  ]
};

​
ProgressPlugin

Show compilation progress: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.ProgressPlugin({
      activeModules: true,
      entries: true,
      modules: true,
      percentBy: 'entries'
    })
  ]
};

​
HotModuleReplacementPlugin

Enable Hot Module Replacement: 
const webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.HotModuleReplacementPlugin()
  ]
};
Usually not needed as it’s automatically enabled with devServer.hot: true.

​
HtmlWebpackPlugin

Generate HTML files with script tags: 
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html',
      filename: 'index.html',
      inject: 'body',
      minify: {
        removeComments: true,
        collapseWhitespace: true
      },
      meta: {
        viewport: 'width=device-width, initial-scale=1'
      }
    })
  ]
};
Multiple HTML files: 
plugins: [
  new HtmlWebpackPlugin({
    template: './src/index.html',
    filename: 'index.html',
    chunks: ['main']
  }),
  new HtmlWebpackPlugin({
    template: './src/admin.html',
    filename: 'admin.html',
    chunks: ['admin']
  })
]

​
MiniCssExtractPlugin

Extract CSS into separate files: 
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader'
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: '[name].[contenthash].css',
      chunkFilename: '[id].[contenthash].css'
    })
  ]
};

​
CopyWebpackPlugin

Copy files and directories to output directory: 
const CopyWebpackPlugin = require('copy-webpack-plugin');

module.exports = {
  plugins: [
    new CopyWebpackPlugin({
      patterns: [
        { from: 'public', to: '' },
        { from: 'src/assets', to: 'assets' },
        {
          from: 'src/manifest.json',
          to: 'manifest.json',
          transform(content) {
            return JSON.stringify({
              ...JSON.parse(content),
              version: process.env.VERSION
            });
          }
        }
      ]
    })
  ]
};

​
CleanWebpackPlugin

Remove build folder before building: 
const { CleanWebpackPlugin } = require('clean-webpack-plugin');

module.exports = {
  plugins: [
    new CleanWebpackPlugin()
  ]
};
In webpack 5, you can use output.clean: true instead.

​
CompressionWebpackPlugin

Prepare compressed versions of assets: 
const CompressionPlugin = require('compression-webpack-plugin');

module.exports = {
  plugins: [
    new CompressionPlugin({
      filename: '[path][base].gz',
      algorithm: 'gzip',
      test: /\.(js|css|html|svg)$/,
      threshold: 10240,
      minRatio: 0.8
    })
  ]
};

​
WebpackBundleAnalyzer

Visualize bundle size: 
const { BundleAnalyzerPlugin } = require('webpack-bundle-analyzer');

module.exports = {
  plugins: [
    new BundleAnalyzerPlugin({
      analyzerMode: 'static',
      openAnalyzer: false,
      reportFilename: 'bundle-report.html'
    })
  ]
};

​
DotenvWebpackPlugin

Load environment variables from .env file: 
const Dotenv = require('dotenv-webpack');

module.exports = {
  plugins: [
    new Dotenv({
      path: './.env',
      safe: true,
      systemvars: true,
      silent: false
    })
  ]
};

​
ESLintWebpackPlugin

Run ESLint on build: 
const ESLintPlugin = require('eslint-webpack-plugin');

module.exports = {
  plugins: [
    new ESLintPlugin({
      extensions: ['js', 'jsx', 'ts', 'tsx'],
      fix: true,
      emitWarning: true,
      failOnError: false
    })
  ]
};

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ForkTsCheckerWebpackPlugin

Run TypeScript type checker on a separate process: 
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');

module.exports = {
  plugins: [
    new ForkTsCheckerWebpackPlugin({
      async: false,
      typescript: {
        configFile: 'tsconfig.json'
      }
    })
  ]
};

​
Plugin Patterns

​
Conditional Plugins

webpack.config.js
const isDevelopment = process.env.NODE_ENV === 'development';
const isProduction = process.env.NODE_ENV === 'production';

module.exports = {
  plugins: [
    // Always include
    new HtmlWebpackPlugin(),
    
    // Conditional with ternary
    isProduction 
      ? new MiniCssExtractPlugin()
      : null,
    
    // Conditional with &&
    isDevelopment && new webpack.HotModuleReplacementPlugin(),
    
    // Multiple conditional plugins
    ...(isProduction ? [
      new CompressionPlugin(),
      new BundleAnalyzerPlugin()
    ] : [])
  ].filter(Boolean) // Remove falsy values
};

​
Plugin Composition

webpack.config.js
function getPlugins(env) {
  const plugins = [
    new HtmlWebpackPlugin({
      template: './src/index.html'
    }),
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify(env)
    })
  ];
  
  if (env === 'production') {
    plugins.push(
      new MiniCssExtractPlugin(),
      new CompressionPlugin()
    );
  }
  
  if (env === 'development') {
    plugins.push(
      new webpack.HotModuleReplacementPlugin()
    );
  }
  
  return plugins;
}

module.exports = {
  plugins: getPlugins(process.env.NODE_ENV)
};

​
Environment-Based Configuration

webpack.config.js
const webpack = require('webpack');

module.exports = (env, argv) => {
  const isProduction = argv.mode === 'production';
  
  return {
    plugins: [
      new webpack.DefinePlugin({
        'process.env.API_URL': JSON.stringify(
          isProduction 
            ? 'https://api.production.com'
            : 'https://api.dev.com'
        )
      }),
      new HtmlWebpackPlugin({
        template: './src/index.html',
        minify: isProduction
      })
    ]
  };
};

​
Writing Custom Plugins

Basic plugin structure: 
class MyCustomPlugin {
  apply(compiler) {
    compiler.hooks.done.tap('MyCustomPlugin', (stats) => {
      console.log('Build complete!');
    });
  }
}

module.exports = {
  plugins: [
    new MyCustomPlugin()
  ]
};
Plugin with options: 
class MyPlugin {
  constructor(options) {
    this.options = options;
  }
  
  apply(compiler) {
    compiler.hooks.emit.tapAsync(
      'MyPlugin',
      (compilation, callback) => {
        // Modify compilation
        const { message } = this.options;
        console.log(message);
        callback();
      }
    );
  }
}

module.exports = {
  plugins: [
    new MyPlugin({ message: 'Hello from plugin!' })
  ]
};

​
Common Plugin Combinations

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Production Build

const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const CompressionPlugin = require('compression-webpack-plugin');
const { BundleAnalyzerPlugin } = require('webpack-bundle-analyzer');

module.exports = {
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html',
      minify: true
    }),
    new MiniCssExtractPlugin({
      filename: '[name].[contenthash].css'
    }),
    new CompressionPlugin(),
    new BundleAnalyzerPlugin({
      analyzerMode: 'static',
      openAnalyzer: false
    })
  ]
};

​
Development Build

const webpack = require('webpack');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ESLintPlugin = require('eslint-webpack-plugin');

module.exports = {
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html'
    }),
    new webpack.HotModuleReplacementPlugin(),
    new ESLintPlugin({
      extensions: ['js', 'jsx'],
      fix: true
    })
  ]
};