uglify-loader

library3.0.0jsnpmunverified

A webpack loader that applies UglifyJS minification (with mangling) to individual modules during bundling, as opposed to the webpack UglifyJSPlugin which minifies the entire output after bundling. Version 3.0.0 is the latest stable release, targeting webpack 4+. The loader allows selective minification of application code while preserving third-party libraries, and supports custom UglifyJS options via loader options. It is maintained by the community and sees infrequent updates.

devops

npm install uglify-loader

github ↗package ↗

INSTALL

IMPORT

SIG · UGLIFY-LOADER

uglify-loader

devopsjavascriptv3.0.0

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

default

✓ import uglifyLoader from 'uglify-loader'; // in webpack config as string 'uglify-loader'

✗ const uglifyLoader = require('uglify-loader'); // Not used directly; use string reference

Loader is referenced by name in webpack config, not imported directly.

Webpack configuration using uglify-loader on .js files excluding node_modules, with custom UglifyJS options.

// webpack.config.js module.exports = { module: { rules: [ { test: /\.js$/, exclude: /node_modules/, use: { loader: 'uglify-loader', options: { mangle: true, compress: { sequences: true, dead_code: true, conditionals: true } } } } ] } };

Debug

Known issues

breakinguglify-loader 3.x only supports webpack 4+. Using with webpack 5 may cause issues; consider terser-webpack-plugin instead.

fix

Use terser-webpack-plugin for webpack 4+ or upgrade to webpack 5 compatible minifier.

affects: >=3.0.0

deprecatedLoader options via webpack config property 'uglify-loader' is deprecated in webpack 2+. Use loader options instead.

fix

Move UglifyJS options into the loader's options object in webpack config.

affects: <3.0.0

gotchaThe loader minifies each module individually, which may break global variable references if not careful.

fix

Ensure UglifyJS options handle global definitions properly or use a bundle-level minifier.

affects: *

Errors

Common errors & fixes

Module parse failed: Unexpected token (1:0) You may need an appropriate loader to handle this file type.

uglify-loader expects valid JavaScript input; it cannot handle non-JS files like CSS or TypeScript.

fix

Ensure the test pattern only matches .js files and exclude other file types.

Configuration file had an error: Error: webpack.optimize.UglifyJsPlugin is not a plugin

Confusing uglify-loader with webpack's built-in UglifyJsPlugin.

fix

Use the string 'uglify-loader' in the rules configuration, not the plugin.

Upgrade

Version history

3.0.0latest on npm

Audit

Dependencies

uglify-jsrequiredCore minification library

webpackrequiredLoader runs within webpack build pipeline

Agent activity

9 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/bestander/uglify-loader ↗

packagehttps://www.npmjs.com/package/uglify-loader ↗