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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 MUI 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.

When and how to use tree-shaking?

Tree-shaking of MUI works out of the box in modern frameworks. MUI exposes its full API on the top-level @mui imports. 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 still get an optimized bundle size automatically:

import { Button, TextField } from '@mui/material';

⚠️ The following instructions are only needed if you want to optimize your development startup times or if you are using an older bundler that doesn't support tree-shaking.

Development environment

Development bundles can contain the full library which can lead to slower startup times. This is especially noticeable if you use named imports from @mui/icons-material, which can be up to six times slower than the default import. For example, between the following two imports, the first (named) can be significantly slower than the second (default):

// 🐌 Named
import { Delete } from '@mui/icons-material';

// 🚀 Default
import Delete from '@mui/icons-material/Delete';

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

Option one: use path imports

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

// 🚀 Fast
import Button from '@mui/material/Button';
import TextField from '@mui/material/TextField';

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

import { Button, TextField } from '@mui/material';

This is the option we document in all the demos since it requires no configuration. It is encouraged for library authors that are 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 the main file of @mui/material, 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 deeper is considered private and can cause issues, such as module duplication in your bundle.

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

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

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

If you're using eslint you can catch problematic imports with the no-restricted-imports rule. The following .eslintrc configuration will highlight problematic imports from @mui packages:

{
  "rules": {
    "no-restricted-imports": [
      "error",
      {
        "patterns": ["@mui/*/*/*"]
      }
    ]
  }
}

Option two: use a Babel plugin

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 '@mui/material';

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: '@mui/material',
      libraryDirectory: '',
      camel2DashComponentName: false,
    },
    'core',
  ],
  [
    'babel-plugin-import',
    {
      libraryName: '@mui/icons-material',
      libraryDirectory: '',
      camel2DashComponentName: false,
    },
    'icons',
  ],
];

module.exports = { plugins };

  • babel-plugin-direct-import with the following configuration:

    yarn add -D babel-plugin-direct-import

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

    const plugins = [
  [
    'babel-plugin-direct-import',
    { modules: ['@mui/material', '@mui/icons-material'] },
  ],
];

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 */
/* eslint-disable react-hooks/rules-of-hooks */
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 commands:

   "scripts": {
-    "start": "react-scripts start",
+    "start": "react-app-rewired start",
-    "build": "react-scripts build",
+    "build": "react-app-rewired build",
-    "test": "react-scripts test",
+    "test": "react-app-rewired test",
     "eject": "react-scripts eject"
  }

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

Available bundles

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

⚠️ Developers are strongly discouraged to import from any of the other bundles directly. Otherwise it's not guaranteed that dependencies used also use legacy or modern bundles. Instead, use these bundles at the bundler level with e.g Webpack's resolve.alias:

{
  resolve: {
    alias: {
      '@mui/base': '@mui/base/legacy',
      '@mui/lab': '@mui/lab/legacy',
      '@mui/material': '@mui/material/legacy',
      '@mui/styled-engine': '@mui/styled-engine/legacy',
      '@mui/system': '@mui/system/legacy',
      '@mui/utils': '@mui/utils/legacy',
    }
  }
}

Modern bundle

The modern bundle can be found under the /modern folder. It targets the latest released versions of evergreen browsers (Chrome, Firefox, Safari, Edge). This can be used to make separate bundles targeting different browsers.

Legacy bundle

If you need to support IE 11 you cannot use the default or modern bundle without transpilation. However, you can use the legacy bundle found under the /legacy folder. You don't need any additional polyfills.