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Minimizing Bundle Size

Learn more about the tools you can leverage to reduce the bundle size.

Bundle size matters

The bundle size of Material-UI is taken very seriously. Size snapshots are taken on every commit for every package and critical parts of those packages (view the latest snapshot). Combined with dangerJS we can inspect detailed bundle size changes on every Pull Request.

How to reduce the bundle size?

For convenience, Material-UI exposes its full API on the top-level material-ui import. If you're using ES6 modules and a bundler that supports tree-shaking (webpack >= 2.x, parcel with a flag) you can safely use named imports and expect only a minimal set of Material-UI components in your bundle:

import { Button, TextField } from '@material-ui/core';

⚠️ Be aware that tree-shaking is an optimization that is usually only applied to production bundles. Development bundles will contain the full library which can lead to slower startup times. This is especially noticeable if you import from @material-ui/icons. Startup times can be approximately 6x slower than without named imports from the top-level API.

If this is an issue for you, you have various options:

Option 1

You can use path imports to avoid pulling in unused modules. For instance, use:

// 🚀 Fast
import Button from '@material-ui/core/Button';
import TextField from '@material-ui/core/TextField';

instead of top level imports (without a Babel plugin):

import { Button, TextField } from '@material-ui/core';

This is the option we document in all the demos, since it requires no configuration. It is encouraged for library authors extending the components. Head to Option 2 for the approach that yields the best DX and UX.

While importing directly in this manner doesn't use the exports in @material-ui/core/index.js, this file can serve as a handy reference as to which modules are public.

Be aware that we only support first and second level imports. Anything below is considered private and can cause module duplication in your bundle.

// ✅ OK
import { Add as AddIcon } from '@material-ui/icons';
import { Tabs } from '@material-ui/core';
//                                 ^^^^ 1st or top-level

// ✅ OK
import AddIcon from '@material-ui/icons/Add';
import Tabs from '@material-ui/core/Tabs';
//                                  ^^^^ 2nd level

// ❌ NOT OK
import TabIndicator from '@material-ui/core/Tabs/TabIndicator';
//                                               ^^^^^^^^^^^^ 3rd level

Option 2

This option provides the best User Experience and Developer Experience:

  • UX: The Babel plugin enables top level tree-shaking even if your bundler doesn't support it.
  • DX: The Babel plugin makes startup time in dev mode as fast as Option 1.
  • DX: This syntax reduces the duplication of code, requiring only a single import for multiple modules. Overall, the code is easier to read, and you are less likely to make a mistake when importing a new module.
    import { Button, TextField } from '@material-ui/core';

However, you need to apply the two following steps correctly.

1. Configure Babel

Pick one of the following plugins:

  • babel-plugin-import with the following configuration:

    yarn add -D babel-plugin-import

    Create a .babelrc.js file in the root directory of your project:

    const plugins = [
      [
        'babel-plugin-import',
        {
          'libraryName': '@material-ui/core',
          // Use "'libraryDirectory': ''," if your bundler does not support ES modules
          'libraryDirectory': 'esm',
          'camel2DashComponentName': false
        },
        'core'
      ],
      [
        'babel-plugin-import',
        {
          'libraryName': '@material-ui/icons',
          // Use "'libraryDirectory': ''," if your bundler does not support ES modules
          'libraryDirectory': 'esm',
          'camel2DashComponentName': false
        },
        'icons'
      ]
    ];
    
    module.exports = {plugins};
  • babel-plugin-transform-imports with the following configuration:

    yarn add -D babel-plugin-transform-imports

    Create a .babelrc.js file in the root directory of your project:

    const plugins = [
      [
        'babel-plugin-transform-imports',
        {
          '@material-ui/core': {
            // Use "transform: '@material-ui/core/${member}'," if your bundler does not support ES modules
            'transform': '@material-ui/core/esm/${member}',
            'preventFullImport': true
          },
          '@material-ui/icons': {
            // Use "transform: '@material-ui/icons/${member}'," if your bundler does not support ES modules
            'transform': '@material-ui/icons/esm/${member}',
            'preventFullImport': true
          }
        }
      ]
    ];
    
    module.exports = {plugins};

If you are using Create React App, you will need to use a couple of projects that let you use .babelrc configuration, without ejecting.

yarn add -D react-app-rewired customize-cra

Create a config-overrides.js file in the root directory:

  /* config-overrides.js */
  const { useBabelRc, override } = require('customize-cra')

  module.exports = override(
    useBabelRc()
  );

If you wish, babel-plugin-import can be configured through config-overrides.js instead of .babelrc by using this configuration.

Modify your package.json start command:

  "scripts": {
-  "start": "react-scripts start"
+  "start": "react-app-rewired start"
  }

Note: You may run into errors like these:

Module not found: Can't resolve '@material-ui/core/makeStyles' in '/your/project'

This is because @material-ui/styles is re-exported through core, but the full import is not allowed.

You have an import like this in your code:

  import { makeStyles, createStyles } from '@material-ui/core';

The fix is simple, define the import separately:

  import { makeStyles, createStyles } from '@material-ui/core/styles';

Enjoy significantly faster start times.

2. Convert all your imports

Finally, you can convert your existing codebase to this option with this top-level-imports codemod. It will perform the following diffs:

-import Button from '@material-ui/core/Button';
-import TextField from '@material-ui/core/TextField';
+import { Button, TextField } from '@material-ui/core';

ECMAScript

The package published on npm is transpiled, with Babel, to take into account the supported platforms.

A second version of the components is also published, which you can find under the /es folder. All the non-official syntax is transpiled to the ECMA-262 standard, nothing more. This can be used to make separate bundles targeting different browsers. Older browsers will require more JavaScript features to be transpiled, which increases the size of the bundle. No polyfills are included for ES2015 runtime features. IE11+ and evergreen browsers support all the necessary features. If you need support for other browsers, consider using @babel/polyfill.

⚠️ In order to minimize duplication of code in users' bundles, library authors are strongly discouraged from using the /es folder.