Duplicate Dependencies Webpack Plugin

1.0.2 verified Sat Apr 25 auth: no javascript

A webpack plugin to detect and report duplicated dependencies in the bundle. Version 1.0.2, stable, maintained sporadically. Key differentiator: provides a hook-based architecture for custom reporting, unlike simpler duplicates plugins that only warn. Allows programmatic access to duplicate package data (name, version, root path, bytes) for integration with custom reporters or CI checks. Primarily used in webpack 4 and 5 projects to audit dependency duplication.

Common errors

error TypeError: DuplicateReporterPlugin is not a constructor ↓

cause Incorrect import or usage of DuplicateReporterPlugin as default export without destructuring.

fix

Use const { DuplicateReporterPlugin } = require('duplicate-dependencies-webpack-plugin') or const Plugin = require('duplicate-dependencies-webpack-plugin'); new Plugin()

error Error: Cannot find module 'duplicate-dependencies-webpack-plugin' ↓

cause Plugin not installed.

fix

Run npm install duplicate-dependencies-webpack-plugin --save-dev

Warnings

gotcha Plugin adds overhead for large bundles; may slow down build. ↓

fix Use only in development or CI, not production builds.

deprecated Webpack 4 hooks: compilation.hooks.additionalAssets may be deprecated in future webpack versions. ↓

fix Test with webpack 5; plugin is compatible.

Install

npm install duplicate-dependencies-webpack-plugin

yarn add duplicate-dependencies-webpack-plugin

pnpm add duplicate-dependencies-webpack-plugin

Imports

DuplicateReporterPlugin

wrong

const { DuplicateReporterPlugin } = require('duplicate-dependencies-webpack-plugin')

correct

import { DuplicateReporterPlugin } from 'duplicate-dependencies-webpack-plugin'

Named export; use destructured import or require. ESM and CJS both supported.

default import

wrong

const DuplicatePlugin = require('duplicate-dependencies-webpack-plugin').default

correct

import DuplicatePlugin from 'duplicate-dependencies-webpack-plugin'

Default export is the plugin constructor; in CJS, require returns the same as default export.

getHooks

wrong

DuplicatePlugin.getHooks // do not call statically without compilation

correct

import DuplicatePlugin from 'duplicate-dependencies-webpack-plugin'; DuplicatePlugin.getHooks(compilation)

getHooks is a static method on the plugin class, requires compilation object from webpack.

Quickstart

Minimal webpack config adding DuplicateReporterPlugin to detect duplicate dependencies in output.

const { DuplicateReporterPlugin } = require('duplicate-dependencies-webpack-plugin');

module.exports = {
  entry: './src/index.js',
  output: { filename: 'bundle.js' },
  plugins: [new DuplicateReporterPlugin()]
};