How To Use Custom webpack Configurations with Angular CLI Builders



The Angular CLI can create a new Angular project and it will handle the webpack configuration. However, there are situations where you will want to add custom webpack functionality.

For the purposes of this article, you will learn how to use the moment.js library and remove unused locales to create a smaller bundle size.

Note: moment.js is a popular library for handling date and time. However, the current project status suggests that there may be other libraries with modern approaches that may suit your project better depending on your target audience. For educational purposes in reducing bundle sizes, this article will continue to use moment.js.

In this article, you will take an existing Angular CLI-generated project and use @angular-builders/custom-webpack for a custom webpack configuration.


To complete this tutorial, you will need:

This tutorial was verified with Angular v10.2.0, @angular-builders/custom-webpack v10.0.1, moment.js v2.29.1, and moment-locales-webpack-plugin v1.2.0.

Step 1 — Setting Up the Project

You can use @angular/cli to create a new Angular Project.

In your terminal window, use the following command:

  • npx @angular/cli new AngularCustomWebpackConfig --style=css --routing=false --skip-tests

This will configure a new Angular project with styles set to “CSS” (as opposed to “Sass”, Less", or “Stylus”), no routing, and skipping tests.

Navigate to the newly created project directory:

  • cd AngularCustomWebpackConfig

You can then install moment.js to your project and import this into your project:

  • npm install moment@2.29.1

To reduce the size of the moment.js library, you will need to also add moment-locales-webpack-plugin as a devDependency:

  • npm install --save-dev moment-locales-webpack-plugin@1.2.0

In order to use a custom webpack config, you will need to add @angular-builders/custom-webpack and @angular-builders/dev-server to your project as devDependency packages:

  • npm install --save-dev @angular-builders/custom-webpack@10.0.1

At this point you should have an Angular project generated by Angular CLI, moment.js, moment-locales-webpack-plugin, and @angular-builders/custom-webpack.

Step 2 — Building a Localized Clock Display

The example project for this article will display date and time information in French.

Open app.component.ts in your code editor and import moment and use it to display the current time in the format of the month name, day of the month, year, and time (LLL) using the French (fr) locale:

import { Component, OnInit } from '@angular/core';

import * as moment from 'moment';

  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
export class AppComponent implements OnInit {
  currentTimeFRLocale: string;

  ngOnInit(): void {
    this.currentTimeFRLocale = moment().format('LLL');

Then, open app.component.html in your code editor and use the currentTimeFRLocale:

<h1>{{ currentTimeFRLocale }}</h1>

This code will display the date and time string.

Run the application:

  • npm start

And open it in a browser:

Screenshot of Angular application displaying: 8 avril 2019 15:29

Once you verify that your application is working as expected, take a note of the values for main.js and vendor.js in the console;

Unmodified Webpack Output
chunk {main} main.js, main.js.map (main) 15 kB [initial] [rendered] ... chunk {vendor} vendor.js, vendor.js.map (vendor) 3.04 MB [initial] [rendered]

The vendor file, which contains moment.js, is 3.04 MB in size.

Step 3 — Modifying a Localized Clock Display with a Custom webpack Configuration

moment.js supports many locales by default. If the audience for your project does not require certain languages, removing the locales that are not necessary can help reduce file sizes. Smaller file sizes in turn will let your application load quicker for the end-user.

With your code editor, create a new custom-webpack.config.js file and add the following lines of code;

const MomentLocalesPlugin = require('moment-locales-webpack-plugin');

module.exports = {
  plugins: [
    new MomentLocalesPlugin({
      localesToKeep: ['fr']

This will require the moment-locales-webpack-plugin and use it to keep the fr locale - which will be date and time terms in the French language.

Next, you will need to modify angular.json to use this new configuration.

Open angular.json in your code editor. Inside of the architect/build object, update the builder from @angular-devkit/build-angular:browser to @angular-builders/custom-webpack:browser and add the customWebpackConfig key:

"architect": {
  "build": {
    "builder": "@angular-builders/custom-webpack:browser",
    "options": {
      "customWebpackConfig": {
        "path": "./custom-webpack.config.js",
        "replaceDuplicatePlugins": true
      // ...
    // ...
  // ...

This will build the application with the custom webpack configuration.

You will also want to apply the custom webpack configuration when developing locally.

Revisit the angular.json in your code editor. Inside of the architect/serve object, update the builder from @angular-devkit/build-angular:dev-server to @angular-builders/custom-webpack:dev-server:

"architect": {
  // ...
  "serve": {
    "builder": "@angular-builders/custom-webpack:dev-server",
    "options": {
      "browserTarget": "AngularCustomWebpackConfig:build"
    "configurations": {
      "production": {
        "browserTarget": "AngularCustomWebpackConfig:build:production"
  // ...

At this point, your application knows to use the @angular-builders/custom-webpack instead of @angular-devkit/build-angular and where to look for the custom webpack configuration.

Note: Previously, the @angular-builders/dev-server package was required. However, since version 8, it has been deprecated and @angular-builders/custom-webpack:dev-server should be used instead.

Run the application:

  • npm start

Once you verify that your application is working as expected, take note of the values for main.js and vendor.js in the console.

Looking back, the unmodified webpack configuration generated main.js and vendor.js with the following file sizes:

Unmodified Webpack Output
chunk {main} main.js, main.js.map (main) 15 kB [initial] [rendered] ... chunk {vendor} vendor.js, vendor.js.map (vendor) 3.04 MB [initial] [rendered]

Now, with the customized webpack configuration, the main.js and vendor.js file sizes have been reduced:

Custom Webpack Output
chunk {main} main.js, main.js.map (main) 9.91 kB [initial] [rendered] ... chunk {vendor} vendor.js, vendor.js.map (vendor) 2.55 MB [initial] [rendered]

That is a difference of 5 kB and 490 kB respectively.


In this article, you learned how to use @angular-builders/custom-webpack to use a custom webpack configuration. Using a custom webpack configuration can offer you greater control over your project than the defaults generated with Angular CLI.

If you’d like to learn more about Angular, check out our Angular topic page for exercises and programming projects.

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