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Neutrino React Preset

@neutrinojs/react is a Neutrino preset that supports building React web applications.

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  • Zero upfront configuration necessary to start developing and building a React web app
  • Modern Babel compilation adding JSX, object rest spread syntax, and class properties.
  • Support for React Hot Loader
  • Write JSX in .js or .jsx files
  • Extends from @neutrinojs/web
  • Modern Babel compilation supporting ES modules, last 2 major browser versions, async functions, and dynamic imports
  • webpack loaders for importing HTML, CSS, images, icons, and fonts
  • webpack Dev Server during development
  • Automatic creation of HTML pages, no templating necessary
  • Automatic stylesheet extraction; importing stylesheets into modules creates bundled external stylesheets
  • Pre-configured to support CSS Modules via *.module.css file extensions
  • Hot Module Replacement support including CSS
  • Tree-shaking to create smaller bundles
  • Production-optimized bundles with minification, easy chunking, and scope-hoisted modules for faster execution
  • Easily extensible to customize your project as needed

Important! If you need polyfills in your code, consider including core-js in your package.json. This is will configure @babel/preset-env to automatically include polyfills based on usage. *


  • Node.js 10+
  • Yarn v1.2.1+, or npm v5.4+
  • Neutrino 9
  • webpack 4
  • webpack-cli 3
  • webpack-dev-server 3


The fastest way to get started is by using the create-project scaffolding tool. Don’t want to use the CLI helper? No worries, we have you covered with the manual installation.


Run the following command to start the process. Substitute <directory-name> with the directory name you wish to create for this project.


❯ yarn create @neutrinojs/project <directory-name>

Note: The create command is a shorthand that helps you do two things at once. See the Yarn create docs for more details.


npx comes pre-installed with npm. If you’re running an older version of npm, then npm install -g npm to update to the latest version.

❯ npx @neutrinojs/create-project <directory-name>

The CLI helper will prompt for the project to scaffold, and will offer to set up a test runner as well as linting to your project. Refer to the Create new project section for details on all available options.

Manual Installation

@neutrinojs/react can be installed via the Yarn or npm clients. Inside your project, make sure that the Neutrino and webpack related dependencies below are installed as development dependencies. You will also need React and React DOM for actual React development.


❯ yarn add --dev neutrino @neutrinojs/react webpack webpack-cli webpack-dev-server
❯ yarn add react react-dom


❯ npm install --save-dev neutrino @neutrinojs/react webpack webpack-cli webpack-dev-server
❯ npm install --save react react-dom

After that, add a new directory named src in the root of the project, with a single JS file named index.js in it.

❯ mkdir src && touch src/index.js

This React preset exposes an element in the page with an ID of root to which you can mount your application. Edit your src/index.js file with the following:

import { render } from 'react-dom';

render(<h1>Hello world!</h1>, document.getElementById('root'));

Now edit your project's package.json to add commands for starting and building the application:

  "scripts": {
    "start": "webpack-dev-server --mode development --open",
    "build": "webpack --mode production"

Then create a .neutrinorc.js file alongside package.json, which contains your Neutrino configuration:

const react = require('@neutrinojs/react');

module.exports = {
  use: [react()],

And create a webpack.config.js file, that uses the Neutrino API to access the generated webpack config:

const neutrino = require('neutrino');

module.exports = neutrino().webpack();

Start the app, then open a browser to the address in the console:


❯ yarn start


❯ npm start

Project Layout

@neutrinojs/react follows the standard project layout specified by Neutrino. This means that by default all project source code should live in a directory named src in the root of the project. This includes JavaScript files, CSS stylesheets, images, and any other assets that would be available to import your compiled project.


@neutrinojs/react builds static assets to the build directory by default when running yarn build. You can either serve or deploy the contents of this build directory as a static site.

Static assets

If you wish to copy files to the build directory that are not imported from application code, use the @neutrinojs/copy preset alongside this one.

Deployment Path

By default @neutrinojs/react assumes that your application will be deployed at the root of a domain (eg:, and so sets webpack's output.publicPath to '/', which means assets will be loaded from the site root using absolute paths.

If your app is instead deployed within a subdirectory, you will need to adjust the publicPath preset option. For example if your app is hosted at, you will need to set publicPath to '/my-app/'.

Alternatively, if you would like your app to be able to be served from any location, and are not using the HTML5 pushState history API or client-side routing, then you can set publicPath to the empty string, which will cause relative asset paths to be used instead.

Preset options

You can provide custom options and have them merged with this preset's default options to easily affect how this preset builds. You can modify React preset settings from .neutrinorc.js by overriding with an options object. The following shows how you can pass an options object to the React preset and override its options. See the Web documentation for specific options you can override with this object.

const react = require('@neutrinojs/react');

module.exports = {
  use: [
      /* preset options */

      // Example: disable Hot Module Replacement
      hot: false,

      // Controls webpack's `output.publicPath` setting.
      // See the "Deployment Path" section above for more info.
      publicPath: '/',

      // Example: change the page title
      html: {
        title: 'Epic React App',

      // Target specific browsers with @babel/preset-env
      targets: {
        browsers: ['last 1 Chrome versions', 'last 1 Firefox versions'],

      // Add additional Babel plugins, presets, or env options
      babel: {
        // Override options for @babel/preset-env:
        presets: [
              useBuiltIns: 'usage',


To override the build configuration, start with the documentation on customization. @neutrinojs/react does not use any additional named rules, loaders, or plugins that aren't already in use by the Web preset. See the Web documentation customization for preset-specific configuration to override.

For details on merging and overriding Babel configuration, such as supporting decorator syntax, read more about using the compile-loader merge once you are comfortable customizing your build.

If the need arises, you can also compile node_modules by referring to the relevant compile-loader documentation.

Advanced configuration

By following the customization guide and knowing the rule, loader, and plugin IDs from @neutrinojs/web, you can override and augment the build by providing a function to your .neutrinorc.js use array. You can also make these changes from the Neutrino API in custom middleware.

By default Neutrino, and therefore this preset, creates a single main index entry point to your application, and this maps to the index.* file in the src directory. The extension is resolved by webpack. This value is provided by neutrino.options.mains at neutrino.options.mains.index.

If you wish to output multiple pages, you can configure them like so:

const react = require('@neutrinojs/react');

module.exports = {
  options: {
    mains: {
      index: {
        // outputs index.html from src/index.*
        entry: 'index',
        // Additional options are passed to html-webpack-plugin, and override
        // any defaults set via the preset's `html` option.
        title: 'Site Homepage',
      admin: {
        // outputs admin.html from src/admin.*
        entry: 'admin',
        title: 'Admin Dashboard',
      account: {
        // outputs account.html from src/user.* using a custom HTML template.
        entry: 'user',
        inject: true,
        template: 'my-custom-template.html',
  use: [react()],


External dependencies are automatically split into separate chunks from the application code, by the new webpack SplitChunksPlugin.

Example: The splitChunks settings can be adjusted like so:

const react = require('@neutrinojs/react');

module.exports = {
  use: [
    (neutrino) => {
        splitChunks: {
          // Decrease the minimum size before extra chunks are created, to 10KB
          minSize: 10000,


@babel/preset-react has its own useBuiltIns option for polyfilling other Babel plugins. Don't confuse it with the useBuiltIns option for @babel/preset-env.

Hot Module Replacement

While @neutrinojs/react supports Hot Module Replacement for your app using React Hot Loader, it does require some application-specific changes in order to operate.

First, install react-hot-loader as a dependency, this must be React Hot Loader v4+:


❯ yarn add react-hot-loader


❯ npm install --save react-hot-loader

Neutrino will then automatically load React Hot Loader then next time a build is performed. Next, you need to mark your root component as hot-exported.

For example, if your src/index main entry renders a root component from App.jsx, then the exported component needs to have a hot export:

// src/App.jsx
import React from 'react';
import { hot } from 'react-hot-loader';

const App = () => <div>Hello World!</div>;

export default hot(module)(App);

See the React Hot Loader docs for any API specifics on hot reloading other components.


This preset is part of the neutrino repository, a monorepo containing all resources for developing Neutrino and its core presets and middleware. Follow the contributing guide for details.