diff --git a/src/content/reference/react-dom/server/renderToPipeableStream.md b/src/content/reference/react-dom/server/renderToPipeableStream.md index 84b8873a6fd..df148494983 100644 --- a/src/content/reference/react-dom/server/renderToPipeableStream.md +++ b/src/content/reference/react-dom/server/renderToPipeableStream.md @@ -292,9 +292,9 @@ Streaming does not need to wait for React itself to load in the browser, or for Suspense **does not** detect when data is fetched inside an Effect or event handler. -The exact way you would load data in the `Posts` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +The exact way you would load data in the `Posts` component above depends on your framework. If you use a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with [`use`](/reference/react/use) as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) diff --git a/src/content/reference/react-dom/server/renderToReadableStream.md b/src/content/reference/react-dom/server/renderToReadableStream.md index f3e862124af..73019721ab7 100644 --- a/src/content/reference/react-dom/server/renderToReadableStream.md +++ b/src/content/reference/react-dom/server/renderToReadableStream.md @@ -291,9 +291,9 @@ Streaming does not need to wait for React itself to load in the browser, or for Suspense **does not** detect when data is fetched inside an Effect or event handler. -The exact way you would load data in the `Posts` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +The exact way you would load data in the `Posts` component above depends on your framework. If you use a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with [`use`](/reference/react/use) as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) diff --git a/src/content/reference/react-dom/static/prerender.md b/src/content/reference/react-dom/static/prerender.md index 8ad47aa15f3..8192b491280 100644 --- a/src/content/reference/react-dom/static/prerender.md +++ b/src/content/reference/react-dom/static/prerender.md @@ -283,9 +283,9 @@ Imagine that `` needs to load some data, which takes some time. Ideally Suspense **does not** detect when data is fetched inside an Effect or event handler. -The exact way you would load data in the `Posts` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +The exact way you would load data in the `Posts` component above depends on your framework. If you use a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with [`use`](/reference/react/use) as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) diff --git a/src/content/reference/react-dom/static/prerenderToNodeStream.md b/src/content/reference/react-dom/static/prerenderToNodeStream.md index 7a31f66a1e4..6336b680bd9 100644 --- a/src/content/reference/react-dom/static/prerenderToNodeStream.md +++ b/src/content/reference/react-dom/static/prerenderToNodeStream.md @@ -284,9 +284,9 @@ Imagine that `` needs to load some data, which takes some time. Ideally Suspense **does not** detect when data is fetched inside an Effect or event handler. -The exact way you would load data in the `Posts` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +The exact way you would load data in the `Posts` component above depends on your framework. If you use a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with [`use`](/reference/react/use) as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) diff --git a/src/content/reference/react/Activity.md b/src/content/reference/react/Activity.md index 127a4b8d0ae..0ef8dcbef5c 100644 --- a/src/content/reference/react/Activity.md +++ b/src/content/reference/react/Activity.md @@ -763,9 +763,9 @@ Pre-rendering components with hidden Activity boundaries is a powerful way to re Activity **does not** detect data that is fetched inside an Effect. -The exact way you would load data in the `Posts` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +The exact way you would load data in the `Posts` component above depends on your framework. If you use a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with [`use`](/reference/react/use) as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) diff --git a/src/content/reference/react/Suspense.md b/src/content/reference/react/Suspense.md index c2fc0b6ef55..91ed2d2ae90 100644 --- a/src/content/reference/react/Suspense.md +++ b/src/content/reference/react/Suspense.md @@ -29,8 +29,10 @@ title: #### Caveats {/*caveats*/} +- Suspense does not detect when data is fetched inside an Effect or event handler. It only activates for the [resources listed below.](#what-activates-a-suspense-boundary) - React does not preserve any state for renders that got suspended before they were able to mount for the first time. When the component has loaded, React will retry rendering the suspended tree from scratch. - If Suspense was displaying content for the tree, but then it suspended again, the `fallback` will be shown again unless the update causing it was caused by [`startTransition`](/reference/react/startTransition) or [`useDeferredValue`](/reference/react/useDeferredValue). +- Once React shows a `fallback`, it waits at least 300ms before replacing it with the resolved content, so that boundaries resolving within that window are [revealed together](/blog/2025/10/01/react-19-2#batching-suspense-boundaries-for-ssr) rather than one at a time. - If React needs to hide the already visible content because it suspended again, it will clean up [layout Effects](/reference/react/useLayoutEffect) in the content tree. When the content is ready to be shown again, React will fire the layout Effects again. This ensures that Effects measuring the DOM layout don't try to do this while the content is hidden. - React includes under-the-hood optimizations like *Streaming Server Rendering* and *Selective Hydration* that are integrated with Suspense. Read [an architectural overview](https://github.com/reactwg/react-18/discussions/37) and watch [a technical talk](https://www.youtube.com/watch?v=pj5N-Khihgc) to learn more. @@ -203,22 +205,221 @@ async function getAlbums() { - +--- + +### What activates a Suspense boundary {/*what-activates-a-suspense-boundary*/} -**Only Suspense-enabled data sources will activate the Suspense component.** They include: +A Suspense boundary waits for its content to be ready before revealing it. Any of the following blocks a boundary's content from being revealed: -- Data fetching with Suspense-enabled frameworks like [Relay](https://relay.dev/docs/guided-tour/rendering/loading-states/) and [Next.js](https://nextjs.org/docs/app/building-your-application/routing/loading-ui-and-streaming#streaming-with-suspense) -- Lazy-loading component code with [`lazy`](/reference/react/lazy) -- Reading the value of a cached Promise with [`use`](/reference/react/use) +- Lazy-loading component code with [`lazy`](/reference/react/lazy). +- Reading a Promise with [`use`](/reference/react/use), including data streamed from [Server Components](/reference/rsc/server-components) and integrations from frameworks like [Relay](https://relay.dev/docs/guided-tour/rendering/loading-states/). +- Loading a stylesheet rendered with [`` and a `precedence` prop.](/reference/react-dom/components/link#special-rendering-behavior) React blocks the boundary until the stylesheet loads, up to a timeout. +- Loading fonts. React blocks a streamed boundary until [`document.fonts.ready`](https://developer.mozilla.org/en-US/docs/Web/API/FontFaceSet/ready) resolves, up to a timeout. Fonts also block a [``](/reference/react/ViewTransition) update. +- Streaming a large boundary's HTML during server rendering. React reveals the content as the HTML arrives. +- Loading an image, where the `src` blocks the boundary until the image loads. This behavior is not enabled by default. When enabled, an `onLoad` handler opts an image out, and images in a [``](/reference/react/ViewTransition) update opt in automatically. +- Performing CPU-bound render work inside a `` boundary marked with the `defer` prop. + + -Suspense **does not** detect when data is fetched inside an Effect or event handler. +#### What is a Suspense-enabled framework? {/*what-is-a-suspense-enabled-framework*/} -The exact way you would load data in the `Albums` component above depends on your framework. If you use a Suspense-enabled framework, you'll find the details in its data fetching documentation. +A *Suspense-enabled framework* reads data with [`use`](/reference/react/use) under the hood, so that reading data in a component activates the nearest boundary. The exact way you load data in the `Albums` component above depends on your framework, and you'll find the details in its data fetching documentation. -Suspense-enabled data fetching without the use of an opinionated framework is not yet supported. The requirements for implementing a Suspense-enabled data source are unstable and undocumented. An official API for integrating data sources with Suspense will be released in a future version of React. +Without a framework, you can read a Promise with `use` directly, as long as the Promise is [cached so the same instance is reused across renders.](/reference/react/use#caching-promises-for-client-components) +For example, both boundaries below are set up identically. The one on the left activates because its content reads a Promise with `use`, so it shows the `fallback` while loading. The one on the right fetches the same data inside an Effect, which Suspense can't detect, so its `fallback` never appears and the albums simply show up once the fetch resolves: + + + +```js +import { Suspense } from 'react'; +import Albums from './Albums.js'; +import EffectAlbums from './EffectAlbums.js'; + +export default function App() { + return ( +
+
+

Reads a Promise with use

+ }> + + +
+
+

Fetches in an Effect

+ }> + + +
+
+ ); +} + +function Loading() { + return

🌀 Loading...

; +} +``` + +```js src/Albums.js active +import { use } from 'react'; +import { fetchData } from './data.js'; + +export default function Albums({ artistId }) { + // Reading the Promise with `use` activates + // the Suspense boundary while it loads. + const albums = use(fetchData(`/${artistId}/albums`)); + return ( +
    + {albums.map(album => ( +
  • + {album.title} ({album.year}) +
  • + ))} +
+ ); +} +``` + +```js src/EffectAlbums.js +import { useState, useEffect } from 'react'; +import { fetchData } from './data.js'; + +export default function EffectAlbums({ artistId }) { + const [albums, setAlbums] = useState([]); + + useEffect(() => { + let active = true; + fetchData(`/${artistId}/albums`).then(result => { + if (active) { + setAlbums(result); + } + }); + return () => { + active = false; + }; + }, [artistId]); + + // Suspense can't see this fetch, so its fallback never + // shows. The list stays empty until the data arrives. + return ( +
    + {albums.map(album => ( +
  • + {album.title} ({album.year}) +
  • + ))} +
+ ); +} +``` + +```js src/data.js hidden +// Note: the way you would do data fetching depends on +// the framework that you use together with Suspense. +// Normally, the caching logic would be inside a framework. + +let cache = new Map(); + +export function fetchData(url) { + if (!cache.has(url)) { + cache.set(url, getData(url)); + } + return cache.get(url); +} + +async function getData(url) { + if (url === '/the-beatles/albums') { + return await getAlbums(); + } else { + throw Error('Not implemented'); + } +} + +async function getAlbums() { + // Add a fake delay to make waiting noticeable. + await new Promise(resolve => { + setTimeout(resolve, 3000); + }); + + return [{ + id: 13, + title: 'Let It Be', + year: 1970 + }, { + id: 12, + title: 'Abbey Road', + year: 1969 + }, { + id: 11, + title: 'Yellow Submarine', + year: 1969 + }, { + id: 10, + title: 'The Beatles', + year: 1968 + }, { + id: 9, + title: 'Magical Mystery Tour', + year: 1967 + }, { + id: 8, + title: 'Sgt. Pepper\'s Lonely Hearts Club Band', + year: 1967 + }, { + id: 7, + title: 'Revolver', + year: 1966 + }, { + id: 6, + title: 'Rubber Soul', + year: 1965 + }, { + id: 5, + title: 'Help!', + year: 1965 + }, { + id: 4, + title: 'Beatles For Sale', + year: 1964 + }, { + id: 3, + title: 'A Hard Day\'s Night', + year: 1964 + }, { + id: 2, + title: 'With The Beatles', + year: 1963 + }, { + id: 1, + title: 'Please Please Me', + year: 1963 + }]; +} +``` + +```css +.panels { + display: flex; + gap: 20px; +} + +.panel { + flex: 1; + border: 1px solid #aaa; + border-radius: 6px; + padding: 10px; +} + +.panel h2 { + margin-top: 0; + font-size: 1rem; +} +``` + +
+ --- ### Revealing content together at once {/*revealing-content-together-at-once*/} diff --git a/src/content/reference/react/use.md b/src/content/reference/react/use.md index 1780f82e7b5..c21462d4a3d 100644 --- a/src/content/reference/react/use.md +++ b/src/content/reference/react/use.md @@ -472,7 +472,7 @@ function Albums() { } ``` -Instead, pass a Promise from a cache, a Suspense-enabled framework, or a Server Component: +Instead, pass a Promise from a cache, a [Suspense-enabled framework](/reference/react/Suspense#what-is-a-suspense-enabled-framework), or a Server Component: ```js // ✅ fetchData reads the Promise from a cache. @@ -538,7 +538,7 @@ The `fetchData` function returns the same Promise each time it's called with the -The way you cache Promises depends on the framework you use with Suspense. Frameworks typically provide built-in caching mechanisms. If you don't use a framework, you can use a simple module-level cache like the one above, or a [Suspense-enabled data source](/reference/react/Suspense#displaying-a-fallback-while-content-is-loading). +The way you cache Promises depends on the framework you use with Suspense. Frameworks typically provide built-in caching mechanisms. If you don't use a framework, you can use a simple module-level cache like the one above, or a [Suspense-enabled data source](/reference/react/Suspense#what-is-a-suspense-enabled-framework). diff --git a/src/content/reference/react/useDeferredValue.md b/src/content/reference/react/useDeferredValue.md index 40cb92629b5..c01250459c5 100644 --- a/src/content/reference/react/useDeferredValue.md +++ b/src/content/reference/react/useDeferredValue.md @@ -86,7 +86,7 @@ During updates, the deferred value will "lag behin -This example assumes you use a Suspense-enabled data source: +This example assumes you use a [Suspense-enabled data source](/reference/react/Suspense#what-is-a-suspense-enabled-framework): - Data fetching with Suspense-enabled frameworks like [Relay](https://relay.dev/docs/guided-tour/rendering/loading-states/) and [Next.js](https://nextjs.org/docs/app/getting-started/fetching-data#with-suspense) - Lazy-loading component code with [`lazy`](/reference/react/lazy)