@expo/webpack-config

👋 Welcome to
@expo/webpack-config

Webpack config that's optimized for running universal React and react-native-web projects

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Documentation

To learn more about how to use this Webpack config, check out the docs here: Customizing the Webpack config

Contributing to the docs

• Documentation for the master branch
• Documentation for the latest stable release

API

Running expo customize:web will generate this default config in your project.

const createExpoWebpackConfigAsync = require('@expo/webpack-config');

module.exports = async function (env, argv) {
  const config = await createExpoWebpackConfigAsync(env, argv);
  // Customize the config before returning it.
  return config;
};

Types

Environment

The main options used to configure how @expo/webpack-config works.

name	type	default	description
projectRoot	string	required	Root of the Expo project.
https	boolean	false	Should the dev server use https protocol.
mode	Mode	required	The Webpack mode to bundle the project in.
platform	ExpoPlatform	required	The target platform to bundle for.
pwa	boolean	true	Generate the PWA image assets in production mode.
babel	ExpoBabelOptions	undefined	Control how the default Babel loader is configured.

Environment internal

name	type	default	description
config	ExpoConfig	undefined	The Expo project config, this should be read using @expo/config.
locations	FilePaths	undefined	Paths used to locate where things are.

ExpoPlatform

| type | description | | ------ | ----------- | ----- | ----------- | ---------------------------------------------------------------------------------------------------------- | | 'ios' | 'android' | 'web' | 'electron' | The target platform to bundle for. Native platforms are experimental and require a special native runtime. |

ExpoBabelOptions

Control how the default Babel loader is configured.

name	type	default	description
dangerouslyAddModulePathsToTranspile	string[]	undefined	Add the names of node_modules that should be included transpilation step.

Guides

PWAs

• See the docs for expo-pwa to learn more about creating the assets manually.
• Disable automatic PWA generation with expo build:web --no-pwa.
• expo build:web will automatically skip any PWA asset that's already linked in the project's local web/index.html.
• Having sharp CLI installed globally will speed up asset generation, if it's not installed, Jimp will be used instead.

Chrome PWAs

Manifest.json

The manifest.json will be created using the values in the project's app.config.js:

Generating the manifest.json will be skipped if the following exists in the project's web/index.html:

Show HTML

<link rel="manifest" href="..." />

If the icons array is defined in your manifest.json, then Chrome PWA icon generation will be skipped.

Chrome PWA Icons

Icons will be generated using the file defined in your app.config.js under android.icon and it'll fallback to icon.

Show manifest.json

{
  "icons": [
    {
      "src": "...",
      "sizes": "144x144",
      "type": "image/png"
    },
    {
      "src": "...",
      "sizes": "192x192",
      "type": "image/png"
    },
    {
      "src": "...",
      "sizes": "512x512",
      "type": "image/png"
    }
  ]
}

Favicons

Favicons will be generated using the file defined in your app.config.js under web.favicon and it'll fallback to icon.

Asset generation for Favicons will be individually skipped if any of the following fields exist in your web/index.html:

Show HTML

<link rel="icon" type="image/png" sizes="16x16" href="..." />
<link rel="icon" type="image/png" sizes="32x32" href="..." />
<link rel="shortcut icon" href="..." />

Safari PWAs

Icons will be generated using the file defined in your app.config.js under ios.icon and it'll fallback to icon. The splash screens look at ios.splash and fallback to splash.

Asset generation for Safari PWA icons/splash screens will be individually skipped if any of the following fields exist in your web/index.html:

Icons

Show HTML

<link rel="apple-touch-icon" sizes="180x180" href="..." />

Splash Screens

Show HTML

<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2) and (orientation: portrait)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 3) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 3) and (orientation: portrait)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 2) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio: 2) and (orientation: portrait)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3) and (orientation: portrait)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 736px) and (-webkit-device-pixel-ratio: 3) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 414px) and (device-height: 736px) and (-webkit-device-pixel-ratio: 3) and (orientation: portrait)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 375px) and (device-height: 667px) and (-webkit-device-pixel-ratio: 2) and (orientation: landscape)"
  href="..."
/>
<link
  rel="apple-touch-startup-image"
  media="screen and (device-width: 375px) and (device-height: 667px) and (-webkit-device-pixel-ratio: 2) and (orientation: portrait)"
  href="..."
/>

Include modules

You may find that you want to include universal modules that aren't part of the default modules. You can do this by customizing the Webpack config:

const createExpoWebpackConfigAsync = require('@expo/webpack-config');

module.exports = async function (env, argv) {
  const config = await createExpoWebpackConfigAsync(
    {
      ...env,
      babel: {
        dangerouslyAddModulePathsToTranspile: [
          // Ensure that all packages starting with @evanbacon are transpiled.
          '@evanbacon',
        ],
      },
    },
    argv
  );
  return config;
};

withUnimodules

If you're adding support to some other Webpack config like in Storybook or Gatsby you can use the same process to include custom modules:

const { withUnimodules } = require('@expo/webpack-config/addons');

module.exports = function () {
  const someWebpackConfig = {
    /* Your custom Webpack config */
  };

  // Add Expo support...
  const configWithExpo = withUnimodules(someWebpackConfig, {
    projectRoot: __dirname,
    babel: {
      dangerouslyAddModulePathsToTranspile: [
        // Ensure that all packages starting with @evanbacon are transpiled.
        '@evanbacon',
      ],
    },
  });

  return configWithExpo;
};

This method should be used instead of using the expo.web.build.babel.include field of the app.json.

Modify the babel loader

If you want to modify the babel loader further, you can retrieve it using the helper method getExpoBabelLoader like this:

const createExpoWebpackConfigAsync = require('@expo/webpack-config');
const { getExpoBabelLoader } = require('@expo/webpack-config/utils');

module.exports = async function (env, argv) {
  const config = await createExpoWebpackConfigAsync(env, argv);
  const loader = getExpoBabelLoader(config);
  if (loader) {
    // Modify the loader...
  }
  return config;
};

Service workers

Example of using service workers with Expo: npx create-react-native-app -t with-workbox

This webpack config currently does not supply service workers by default, they can be added to the project locally: Adding Service Workers.

Environment Variables

• EXPO_WEBPACK_DEFINE_ENVIRONMENT_AS_KEYS: Should the define plugin explicitly set environment variables like process.env.FOO instead of creating an object like proces.env: { FOO }. Defaults to false. Next.js uses this to prevent overwriting injected environment variables.
• IMAGE_INLINE_SIZE_LIMIT: By default, images smaller than 10,000 bytes are encoded as a data URI in base64 and inlined in the CSS or JS build artifact. Set this to control the size limit in bytes. Setting it to 0 will disable the inlining of images. This is only used in production.

Exports

addons

For adding features to an existing Webpack config.

withOptimizations

import { withOptimizations } from '@expo/webpack-config/addons';

withAlias

Apply aliases to a Webpack config.

import { withAlias } from '@expo/webpack-config/addons';

withDevServer

import { withDevServer } from '@expo/webpack-config/addons';

withTypeScriptAsync

import { withTypeScriptAsync } from '@expo/webpack-config/addons';

env

Getting the config, paths, mode, and various other settings in your environment.

getConfig

import { getConfig } from '@expo/webpack-config/env';

getMode

import { getMode } from '@expo/webpack-config/env';

validateEnvironment

import { validateEnvironment } from '@expo/webpack-config/env';

getAliases

import { getAliases } from '@expo/webpack-config/env';

getPaths

import { getPaths } from '@expo/webpack-config/env';

getPathsAsync

import { getPathsAsync } from '@expo/webpack-config/env';

getServedPath

import { getServedPath } from '@expo/webpack-config/env';

getPublicPaths

import { getPublicPaths } from '@expo/webpack-config/env';

getProductionPath

import { getProductionPath } from '@expo/webpack-config/env';

getAbsolute

import { getAbsolute } from '@expo/webpack-config/env';

getModuleFileExtensions

import { getModuleFileExtensions } from '@expo/webpack-config/env';

loaders

The module rules used to load various files.

imageLoaderRule

import { imageLoaderRule } from '@expo/webpack-config/loaders';

This is needed for webpack to import static images in JavaScript files. "url" loader works like "file" loader except that it embeds assets smaller than specified limit in bytes as data URLs to avoid requests. A missing test is equivalent to a match.

fallbackLoaderRule

import { fallbackLoaderRule } from '@expo/webpack-config/loaders';

"file" loader makes sure those assets get served by WebpackDevServer. When you import an asset, you get its (virtual) filename. In production, they would get copied to the build folder. This loader doesn't use a "test" so it will catch all modules that fall through the other loaders.

styleLoaderRule

import { styleLoaderRule } from '@expo/webpack-config/loaders';

Default CSS loader.

plugins

import /* */ '@expo/webpack-config/plugins';

Custom versions of Webpack Plugins that are optimized for use with native React runtimes.

ExpoDefinePlugin

import { ExpoDefinePlugin } from '@expo/webpack-config/plugins';

Required for expo-constants https://docs.expo.dev/versions/latest/sdk/constants/. This surfaces the app.json (config) as an environment variable which is then parsed by expo-constants.

ExpoHtmlWebpackPlugin

import { ExpoHtmlWebpackPlugin } from '@expo/webpack-config/plugins';

Generates an index.html file with the

ExpoInterpolateHtmlPlugin

import { ExpoInterpolateHtmlPlugin } from '@expo/webpack-config/plugins';

Add variables to the index.html.

What it does not do

• Gzip compression: This was supported in beta but later removed in favor of hosting providers like Now and Netlify automatically compressing files in the server.

License

The Expo source code is made available under the MIT license. Some of the dependencies are licensed differently, with the BSD license, for example.

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