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8.3.0 • Public • Published

Neutrino Web Preset

@neutrinojs/web is a Neutrino preset that supports building generic applications for the web.

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  • Zero upfront configuration necessary to start developing and building a web app
  • Modern Babel compilation supporting ES modules, last 2 major browser versions, async functions, object rest spread syntax, and dynamic imports
  • webpack loaders for importing HTML, CSS, images, icons, fonts, and web workers
  • 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 Babel minification, easy chunking, and scope-hoisted modules for faster execution
  • Easily extensible to customize your project as needed


  • Node.js v6 LTS, v8, v9
  • Yarn v1.2.1+, or npm v5.4+
  • Neutrino v8


@neutrinojs/web can be installed via the Yarn or npm clients. Inside your project, make sure neutrino and @neutrinojs/web are development dependencies.


❯ yarn add --dev neutrino @neutrinojs/web


❯ npm install --save-dev neutrino @neutrinojs/web

Project Layout

@neutrinojs/web 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 your compiled project.


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

After installing Neutrino and the Web preset, 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 Web 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:

const app = document.createElement('main');
const text = document.createTextNode('Hello world!');

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

  "scripts": {
    "start": "neutrino start --use @neutrinojs/web",
    "build": "neutrino build --use @neutrinojs/web"

If you are using .neutrinorc.js, add this preset to your use array instead of --use flags:

module.exports = {
  use: ['@neutrinojs/web']

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


❯ yarn start
✔ Development server running on: http://localhost:5000
✔ Build completed


❯ npm start
✔ Development server running on: http://localhost:5000
✔ Build completed


@neutrinojs/web builds static assets to the build directory by default when running neutrino build. Using the quick start example above as a reference:

❯ yarn build
✔ Building project completed
Hash: 2e1191cdf700df46370d
Version: webpack 3.5.6
Time: 4145ms
                           Asset       Size    Chunks             Chunk Names
   index.523b6da56c6363aaf056.js    10.1 kB     index  [emitted]  index
 runtime.ce4090a4e87f82940ff0.js    1.51 kB   runtime  [emitted]  runtime
                      index.html  846 bytes            [emitted]

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, you can place them in a directory within src called static. All files in this directory will be copied from src/static to build/static. To change this behavior, specify your own patterns with @neutrinojs/copy.


The @neutrinojs/web preset loads assets relative to the path of your application by setting webpack's output.publicPath to ./. If you wish to load assets instead from a CDN, or if you wish to change to an absolute path for your application, customize your build to override output.publicPath. See the Customizing section below.

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 Web preset settings from .neutrinorc.js by overriding with an options object. Use an array pair instead of a string to supply these options in .neutrinorc.js.

The following shows how you can pass an options object to the Web preset and override its options:

module.exports = {
  use: [
    ['@neutrinojs/web', {
      // Change options for @neutrinojs/env
      env: [],
      // Enables Hot Module Replacement. Set to false to disable
      hot: true,
      polyfills: {
        // Enables fast-async polyfill. Set to false to disable
        async: true
      // Sets webpack's `output.publicPath` and
      // `devServer.publicPath` settings. Useful if you want to
      // serve assets from a non-root location (e.g. `/assets/`)
      publicPath: './',
      // Change options for @neutrinojs/style-loader
      style: {
        // Disabling options.hot will also disable style.hot
        hot: true,
        // Extract CSS to a separate file in production.
        extract: process.env.NODE_ENV === 'production'
      // Change options for @neutrinojs/font-loader
      font: {},
      // Change options for @neutrinojs/image-loader
      image: {},
      // Change options for @neutrinojs/minify
      minify: {
        babel: {},
        style: {},
        image: false
      // Change options for `webpack-manifest-plugin`
      manifest: {},
      // Change options related to generating the HTML document
      // See @neutrinojs/html-template for the defaults
      // used by the Web preset
      html: {},
      // Change options related to starting a webpack-dev-server
      devServer: {
        // Disabling options.hot will also disable devServer.hot
        hot: options.hot,
        // Proxy requests that don't match a known file to the specified backend.
        proxy: 'https://localhost:8000/api/'
      // 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: [
          ['babel-preset-env', {
            modules: false,
            useBuiltIns: true,
            exclude: ['transform-regenerator', 'transform-async-to-generator'],

Example: Disable Hot Module Replacement and change the page title:

module.exports = {
  use: [
    ['@neutrinojs/web', {
      /* preset options */
      // Example: disable Hot Module Replacement
      hot: false,
      // Example: disable image-loader, style-loader, font-loader,
      // font-loader, webpack-manifest-plugin
      image: false,
      style: false,
      font: false,
      manifest: false,
      // Example: Remove console and debugger from output
      minify: {
        babel: {
          removeConsole: true,
          removeDebugger: true,
      // Example: Use a .browserslistrc file with babel-env
      targets: {
        browsers: require('browserslist')()
      // Remove the contents of the output directory prior to building.
      // Set to false to disable cleaning this directory
      clean: {
        paths: [neutrino.options.output]
      // Example: change the page title
      html: {
        title: 'Epic Web App'
      // Example: Proxy webpack-dev-server requests to http://localhost:3000
      devServer: {
        proxy: 'http://localhost:3000'

Dev Server Proxy

If you are handling requests with a server, you may want to set up a proxy for development. See webpack's devServer.proxy for all available options.

Optionally, you may pass a url string (instead of an object) to devServer.proxy. This will proxy all requests through the given url, and set some sensible defaults.

For example:

['@neutrinojs/web', {
  devServer: {
    proxy: 'http://localhost:3000'

Is equivalent to:

['@neutrinojs/web', {
  devServer: {
    proxy: {
      '**': {
        target: 'http://localhost:3000',
        changeOrigin: true,
        headers: {
          'X-Dev-Server-Proxy': 'http://localhost:3000'

The X-Dev-Server-Proxy header can be useful for detecting if your existing app is being requested through the proxy.

Hot Module Replacement

While @neutrinojs/web supports Hot Module Replacement your app, it does require some application-specific changes in order to operate. Your application should define split points for which to accept modules to reload using module.hot:

For example:

import app from './app';
  .appendChild(app('Hello world!'));
if (module.hot) {

Or for all paths:

import app from './app';
  .appendChild(app('Hello world!'));
if (module.hot) {

Using dynamic imports with import() will automatically create split points and hot replace those modules upon modification during development.


To override the build configuration, start with the documentation on customization. @neutrinojs/web creates some conventions to make overriding the configuration easier once you are ready to make changes.

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. This means that the Web preset is optimized toward the use case of single-page applications over multi-page applications. If you wish to output multiple pages, you can detail all your mains in your .neutrinorc.js.

module.exports = {
  options: {
    mains: {
      index: 'index', // outputs index.html from src/index.*
      admin: 'admin', // outputs admin.html from src/admin.*
      account: 'user' // outputs account.html from src/user.*
  use: ['@neutrinojs/web']


The following is a list of rules and their identifiers which can be overridden:

Name Description Environments and Commands
compile Compiles JS files from the src directory using Babel. Contains a single loader named babel. From @neutrinojs/compile-loader. all
html Allows importing HTML files from modules. Contains a single loader named html. From @neutrinojs/html-loader. all
style Allows importing CSS stylesheets from modules. Contains two loaders named style and css which use style-loader and css-loader, respectively. From @neutrinojs/style-loader. all
style-modules Allows importing CSS Modules styles from modules. Contains two loaders named style-modules and css-modules which use style-loader and css-loader, respectively. From @neutrinojs/style-loader. all
img, svg, ico Allows import image files from modules. Each contains a single loader named url. From @neutrinojs/image-loader. all
woff, ttf Allows importing WOFF and TTF font files from modules. Each contains a single loader named url. From @neutrinojs/font-loader. all
eot Allows importing EOT font files from modules. Contains a single loader named file. From @neutrinojs/font-loader. all
worker Allows importing Web Workers automatically with .worker.* extensions. Contains a single loader named worker. all


The following is a list of plugins and their identifiers which can be overridden:

Note: Some plugins are only available in certain environments. To override them, they should be modified conditionally.

Name Description Environments and Commands
env Inject environment variables into source code at process.env, defaults to only inject NODE_ENV. From @neutrinojs/env. all
extract Extracts CSS from JS bundle into a separate stylesheet file. From @neutrinojs/style-loader. all
extract-modules Extracts CSS from JS bundle into a separate stylesheet file. From @neutrinojs/style-loader. all
html-{MAIN_NAME} Automatically generates HTML files for configured entry points. {MAIN_NAME} corresponds to the entry point of each page. By default, there is only a single index main, so this would generate a plugin named html-index. From @neutrinojs/html-template all
named-modules Enables named modules for improved debugging and console output. From @neutrinojs/chunk and @neutrinojs/hot. NODE_ENV production, start command
named-chunks Enables named chunks for improved debugging and console output. From @neutrinojs/chunk. NODE_ENV production
vendor-chunk Creates a separate file/chunk consisting of common modules shared between multiple entry points. From @neutrinojs/chunk. NODE_ENV production
runtime-chunk Creates a separate file/chunk consisting of the webpack manifest-specific code. From @neutrinojs/chunk. NODE_ENV production
name-all Names all remaining modules that do not get named via named-modules. From @neutrinojs/chunk. NODE_ENV production
hot Enables Hot Module Replacement. From @neutrinojs/hot. start command
copy Copies files during build, defaults from src/static to build/static. From @neutrinojs/copy build command
clean Removes the build directory prior to building. From @neutrinojs/clean. build command
babel-minify Minifies source code using BabelMinifyWebpackPlugin. From @neutrinojs/minify. NODE_ENV production
imagemin Optimize any images added by other webpack plugins (e.g. copy-webpack-plugin). From @neutrinojs/minify. Enable with options.minify.style.
optimize-css Minifies css using OptimizeCssAssetsPlugin. From @neutrinojs/minify. NODE_ENV production
module-concat Concatenate the scope of all your modules into one closure and allow for your code to have a faster execution time in the browser. NODE_ENV production
manifest Create a manifest file, via webpack-manifest-plugin. build command

Override configuration

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


By defining an entry point named vendor you can split out external dependencies into a chunk separate from your application code.

Example: Put lodash into a separate "vendor" chunk:

module.exports = {
  use: [
    neutrino => {


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


npm i @neutrinojs/web

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