closure-webpack-plugin

2.6.1 verified Sat Apr 25 auth: no javascript

A webpack plugin integrating Google Closure Compiler and Closure Library for JavaScript optimization and transpilation. Version 2.6.1 (webpack 4 branch) requires google-closure-compiler >=20200830.0.0 and webpack 4.x. Offers three platforms (native, Java, JavaScript) and two modes (STANDARD for minification/transpilation, AGGRESSIVE_BUNDLE for advanced module hoisting and optimization). Unlike TerserPlugin or Babel, it provides full Closure Compiler optimizations including dead code elimination, type checking, and cross-module analysis. Not compatible with webpack 5.

Common errors

error TypeError: ClosurePlugin is not a constructor ↓

cause Importing the plugin incorrectly (using default import instead of require).

fix

Use const ClosurePlugin = require('closure-webpack-plugin');

error Error: Cannot find module 'google-closure-compiler' ↓

cause Required peer dependency not installed.

fix

Run npm install --save-dev google-closure-compiler

error Error: webpack version 5.x is not supported ↓

cause Using the plugin with webpack 5.

fix

Downgrade to webpack 4.x, or use an alternative plugin (e.g., terser-webpack-plugin) for webpack 5.

Warnings

breaking Plugin only works with webpack 4.x; not compatible with webpack 5. ↓

fix Use webpack 4 or switch to an alternative plugin for webpack 5.

gotcha Do not set compiler flags module_resolution, output_wrapper, dependency_mode, create_source_map, module, or entry_point—they are controlled by the plugin and will conflict. ↓

fix Remove these flags from the compiler options object. They are overridden internally.

deprecated The 'platform' option accepts strings 'native', 'java', 'javascript', but old documentation used case-insensitive values. ↓

fix Use lowercase strings as above. The plugin may also accept uppercase but it's not guaranteed.

gotcha AGGRESSIVE_BUNDLE mode hoists require() calls, which can cause out-of-order execution if polyfills or side-effects are interleaved. ↓

fix Ensure modules with side-effects are separated into different chunks or mark them with sideEffects: false in package.json.

gotcha childCompilations defaults to false—plugins like html-webpack-plugin may not get optimized output. ↓

fix Set childCompilations: true or a custom function if child compilations need closure optimization.

Install

npm install closure-webpack-plugin

yarn add closure-webpack-plugin

pnpm add closure-webpack-plugin

Imports

ClosurePlugin

wrong

import ClosurePlugin from 'closure-webpack-plugin';

correct

const ClosurePlugin = require('closure-webpack-plugin');

Package does not provide a default ESM export; require() is required.

ClosurePlugin

wrong

import * as ClosurePlugin from 'closure-webpack-plugin';

correct

import ClosurePlugin = require('closure-webpack-plugin');

In TypeScript, use `import = require()` for proper CommonJS interop; namespace import may fail.

ClosurePlugin as ClosurePlugin
wrong
```
const { default: ClosurePlugin } = require('closure-webpack-plugin');
```
correct
```
const { ClosurePlugin } = require('closure-webpack-plugin');
```
No default export; use named export if the package's TypeScript typings allow it (but check actual typings).

Quickstart

Basic webpack config using closure-webpack-plugin as the minifier with JavaScript platform, STANDARD mode, and debug flags.

const ClosurePlugin = require('closure-webpack-plugin');

module.exports = {
  entry: './src/index.js',
  output: {
    filename: 'bundle.js',
    path: __dirname + '/dist'
  },
  optimization: {
    minimizer: [
      new ClosurePlugin({
        mode: 'STANDARD',
        platform: 'javascript'
      }, {
        // compiler flags
        formatting: 'PRETTY_PRINT',
        debug: true,
        renaming: false
      })
    ]
  }
};