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title: loading.js |
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description: API reference for the loading.js file. |
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The special file `loading.js` helps you create meaningful Loading UI with [React Suspense](https://react.dev/reference/react/Suspense). With this convention, you can show an [instant loading state]( |
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<Image |
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alt="Loading UI" |
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srcLight="/docs/light/loading-ui.png" |
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srcDark="/docs/dark/loading-ui.png" |
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width="1600" |
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height="691" |
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/> |
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```tsx filename="app/feed/loading.tsx" switcher |
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export default function Loading() { |
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return <p>Loading...</p> |
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} |
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``` |
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```jsx filename="app/feed/loading.js" switcher |
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export default function Loading() { |
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return <p>Loading...</p> |
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} |
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``` |
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Inside the `loading.js` file, you can add any light-weight loading UI. You may find it helpful to use the [React Developer Tools](https://react.dev/learn/react-developer-tools) to manually toggle Suspense boundaries. |
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By default, this file is a [Server Component](/docs/app/getting-started/server-and-client-components) - but can also be used as a Client Component through the `"use client"` directive. |
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Loading UI components do not accept any parameters. |
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- The Fallback UI is [prefetched](/docs/app/getting-started/linking-and-navigating |
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- Navigation is interruptible, meaning changing routes does not need to wait for the content of the route to fully load before navigating to another route. |
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- Shared layouts remain interactive while new route segments load. |
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An instant loading state is fallback UI that is shown immediately upon navigation. You can pre-render loading indicators such as skeletons and spinners, or a small but meaningful part of future screens such as a cover photo, title, etc. This helps users understand the app is responding and provides a better user experience. |
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Create a loading state by adding a `loading.js` file inside a folder. |
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<Image |
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alt="loading.js special file" |
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srcLight="/docs/light/loading-special-file.png" |
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srcDark="/docs/dark/loading-special-file.png" |
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width="1600" |
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height="606" |
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/> |
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```tsx filename="app/dashboard/loading.tsx" switcher |
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export default function Loading() { |
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return <LoadingSkeleton /> |
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} |
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``` |
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```jsx filename="app/dashboard/loading.js" switcher |
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export default function Loading() { |
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return <LoadingSkeleton /> |
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} |
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``` |
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In the same folder, `loading.js` will be nested inside `layout.js`. It will automatically wrap the `page.js` file and any children below in a `<Suspense>` boundary. |
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<Image |
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alt="loading.js overview" |
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srcLight="/docs/light/loading-overview.png" |
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srcDark="/docs/dark/loading-overview.png" |
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width="1600" |
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height="768" |
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/> |
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- Next.js will wait for data fetching inside [`generateMetadata`](/docs/app/api-reference/functions/generate-metadata) to complete before streaming UI to the client. This guarantees the first part of a streamed response includes `<head>` tags. |
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- Since streaming is server-rendered, it does not impact SEO. You can use the [Rich Results Test](https://search.google.com/test/rich-results) tool from Google to see how your page appears to Google's web crawlers and view the serialized HTML ([source](https://web.dev/rendering-on-the-web/#seo-considerations)). |
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### Status Codes |
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When streaming, a `200` status code will be returned to signal that the request was successful. |
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The server can still communicate errors or issues to the client within the streamed content itself, for example, when using [`redirect`](/docs/app/api-reference/functions/redirect) or [`notFound`](/docs/app/api-reference/functions/not-found). Since the response headers have already been sent to the client, the status code of the response cannot be updated. This does not affect SEO. |
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### Browser limits |
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[Some browsers](https://bugs.webkit.org/show_bug.cgi?id=252413) buffer a streaming response. You may not see the streamed response until the response exceeds 1024 bytes. This typically only affects “hello world” applications, but not real applications. |
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## Platform Support |
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| Deployment Option | Supported | |
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| ------------------------------------------------------------------- | ----------------- | |
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| [Node.js server](/docs/app/getting-started/deploying#nodejs-server) | Yes | |
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| [Docker container](/docs/app/getting-started/deploying#docker) | Yes | |
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| [Static export](/docs/app/getting-started/deploying#static-export) | No | |
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| [Adapters](/docs/app/getting-started/deploying#adapters) | Platform-specific | |
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Learn how to [configure streaming](/docs/app/guides/self-hosting#streaming-and-suspense) when self-hosting Next.js. |
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## Examples |
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### Streaming with Suspense |
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In addition to `loading.js`, you can also manually create Suspense Boundaries for your own UI components. The App Router supports streaming with [Suspense](https://react.dev/reference/react/Suspense). |
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`<Suspense>` works by wrapping a component that performs an asynchronous action (e.g. fetch data), showing fallback UI (e.g. skeleton, spinner) while it's happening, and then swapping in your component once the action completes. |
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```tsx filename="app/dashboard/page.tsx" switcher |
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import { Suspense } from 'react' |
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import { PostFeed, Weather } from './Components' |
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export default function Posts() { |
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return ( |
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<section> |
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<Suspense fallback={<p>Loading feed...</p>}> |
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<PostFeed /> |
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</Suspense> |
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<Suspense fallback={<p>Loading weather...</p>}> |
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<Weather /> |
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</Suspense> |
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</section> |
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) |
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} |
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``` |
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```jsx filename="app/dashboard/page.js" switcher |
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import { Suspense } from 'react' |
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import { PostFeed, Weather } from './Components' |
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export default function Posts() { |
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return ( |
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<section> |
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<Suspense fallback={<p>Loading feed...</p>}> |
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<PostFeed /> |
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</Suspense> |
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<Suspense fallback={<p>Loading weather...</p>}> |
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<Weather /> |
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</Suspense> |
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</section> |
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) |
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} |
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``` |
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By using Suspense, you get the benefits of: |
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1. **Streaming Server Rendering** - Progressively rendering HTML from the server to the client. |
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2. **Selective Hydration** - React prioritizes what components to make interactive first based on user interaction. |
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For more Suspense examples and use cases, please see the [React Documentation](https://react.dev/reference/react/Suspense). |
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| Version | Changes | |
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| `v13.0.0` | `loading` introduced. | |
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