rsnext/docs/02-app/01-building-your-application/06-optimizing/07-lazy-loading.mdx

---
title: Lazy Loading
description: Lazy load imported libraries and React Components to improve your application's loading performance.
---

{/* The content of this doc is shared between the app and pages router. You can use the `<PagesOnly>Content</PagesOnly>` component to add content that is specific to the Pages Router. Any shared content should not be wrapped in a component. */}

[Lazy loading](https://developer.mozilla.org/docs/Web/Performance/Lazy_loading) in Next.js helps improve the initial loading performance of an application by decreasing the amount of JavaScript needed to render a route.

It allows you to defer loading of **Client Components** and imported libraries, and only include them in the client bundle when they're needed. For example, you might want to defer loading a modal until a user clicks to open it.

There are two ways you can implement lazy loading in Next.js:

1. Using [Dynamic Imports](#nextdynamic) with `next/dynamic`
2. Using [`React.lazy()`](https://react.dev/reference/react/lazy) with [Suspense](https://react.dev/reference/react/Suspense)

By default, Server Components are automatically [code split](https://developer.mozilla.org/docs/Glossary/Code_splitting), and you can use [streaming](/docs/app/building-your-application/routing/loading-ui-and-streaming) to progressively send pieces of UI from the server to the client. Lazy loading applies to Client Components.

## `next/dynamic`

`next/dynamic` is a composite of [`React.lazy()`](https://react.dev/reference/react/lazy) and [Suspense](https://react.dev/reference/react/Suspense). It behaves the same way in the `app` and `pages` directories to allow for incremental migration.

## Examples

<AppOnly>
### Importing Client Components

```jsx filename="app/page.js"
'use client'

import { useState } from 'react'
import dynamic from 'next/dynamic'

// Client Components:
const ComponentA = dynamic(() => import('../components/A'))
const ComponentB = dynamic(() => import('../components/B'))
const ComponentC = dynamic(() => import('../components/C'), { ssr: false })

export default function ClientComponentExample() {
  const [showMore, setShowMore] = useState(false)

  return (
    <div>
      {/* Load immediately, but in a separate client bundle */}
      <ComponentA />

      {/* Load on demand, only when/if the condition is met */}
      {showMore && <ComponentB />}
      <button onClick={() => setShowMore(!showMore)}>Toggle</button>

      {/* Load only on the client side */}
      <ComponentC />
    </div>
  )
}
```

### Skipping SSR

When using `React.lazy()` and Suspense, Client Components will be pre-rendered (SSR) by default.

If you want to disable pre-rendering for a Client Component, you can use the `ssr` option set to `false`:

```jsx
const ComponentC = dynamic(() => import('../components/C'), { ssr: false })
```

### Importing Server Components

If you dynamically import a Server Component, only the Client Components that are children of the Server Component will be lazy-loaded - not the Server Component itself.

```jsx filename="app/page.js"
import dynamic from 'next/dynamic'

// Server Component:
const ServerComponent = dynamic(() => import('../components/ServerComponent'))

export default function ServerComponentExample() {
  return (
    <div>
      <ServerComponent />
    </div>
  )
}
```

### Loading External Libraries

External libraries can be loaded on demand using the [`import()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Operators/import) function. This example uses the external library `fuse.js` for fuzzy search. The module is only loaded on the client after the user types in the search input.

```jsx filename="app/page.js"
'use client'

import { useState } from 'react'

const names = ['Tim', 'Joe', 'Bel', 'Lee']

export default function Page() {
  const [results, setResults] = useState()

  return (
    <div>
      <input
        type="text"
        placeholder="Search"
        onChange={async (e) => {
          const { value } = e.currentTarget
          // Dynamically load fuse.js
          const Fuse = (await import('fuse.js')).default
          const fuse = new Fuse(names)

          setResults(fuse.search(value))
        }}
      />
      <pre>Results: {JSON.stringify(results, null, 2)}</pre>
    </div>
  )
}
```

### Adding a custom loading component

```jsx filename="app/page.js"
import dynamic from 'next/dynamic'

const WithCustomLoading = dynamic(
  () => import('../components/WithCustomLoading'),
  {
    loading: () => <p>Loading...</p>,
  }
)

export default function Page() {
  return (
    <div>
      {/* The loading component will be rendered while  <WithCustomLoading/> is loading */}
      <WithCustomLoading />
    </div>
  )
}
```

### Importing Named Exports

To dynamically import a named export, you can return it from the Promise returned by [`import()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Operators/import) function:

```jsx filename="components/hello.js"
'use client'

export function Hello() {
  return <p>Hello!</p>
}
```

```jsx filename="app/page.js"
import dynamic from 'next/dynamic'

const ClientComponent = dynamic(() =>
  import('../components/hello').then((mod) => mod.Hello)
)
```

</AppOnly>

<PagesOnly>

By using `next/dynamic`, the header component will not be included in the page's initial JavaScript bundle. The page will render the Suspense `fallback` first, followed by the `Header` component when the `Suspense` boundary is resolved.

```jsx
import dynamic from 'next/dynamic'

const DynamicHeader = dynamic(() => import('../components/header'), {
  loading: () => <p>Loading...</p>,
})

export default function Home() {
  return <DynamicHeader />
}
```

> **Good to know**: In `import('path/to/component')`, the path must be explicitly written. It can't be a template string nor a variable. Furthermore the `import()` has to be inside the `dynamic()` call for Next.js to be able to match webpack bundles / module ids to the specific `dynamic()` call and preload them before rendering. `dynamic()` can't be used inside of React rendering as it needs to be marked in the top level of the module for preloading to work, similar to `React.lazy`.

## With named exports

To dynamically import a named export, you can return it from the [Promise](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise) returned by [`import()`](https://github.com/tc39/proposal-dynamic-import#example):

```jsx filename="components/hello.js"
export function Hello() {
  return <p>Hello!</p>
}

// pages/index.js
import dynamic from 'next/dynamic'

const DynamicComponent = dynamic(() =>
  import('../components/hello').then((mod) => mod.Hello)
)
```

## With no SSR

To dynamically load a component on the client side, you can use the `ssr` option to disable server-rendering. This is useful if an external dependency or component relies on browser APIs like `window`.

```jsx
import dynamic from 'next/dynamic'

const DynamicHeader = dynamic(() => import('../components/header'), {
  ssr: false,
})
```

## With external libraries

This example uses the external library `fuse.js` for fuzzy search. The module is only loaded in the browser after the user types in the search input.

```jsx
import { useState } from 'react'

const names = ['Tim', 'Joe', 'Bel', 'Lee']

export default function Page() {
  const [results, setResults] = useState()

  return (
    <div>
      <input
        type="text"
        placeholder="Search"
        onChange={async (e) => {
          const { value } = e.currentTarget
          // Dynamically load fuse.js
          const Fuse = (await import('fuse.js')).default
          const fuse = new Fuse(names)

          setResults(fuse.search(value))
        }}
      />
      <pre>Results: {JSON.stringify(results, null, 2)}</pre>
    </div>
  )
}
```

</PagesOnly>