React 19.2

September 30, 2025 by The React Team

This is our third release in the last year, following React 19 in December and React 19.1 in June. In this post, we’ll give an overview of the new features in React 19.2, and highlight some notable changes.

• New Features
  • <Activity />
  • React Performance Tracks
  • useEffectEvent
  • cacheSignal
• Notable Changes
  • Batching Suspense Boundaries for SSR
  • SSR: Web Streams support for Node
  • Update the default useId prefix
• Changelog

New Features

<Activity />

<Activity> lets you break your app into “activities” that can be controlled and prioritized.

You can use Activity as an alternative to conditionally rendering parts of your app:

// Before
{isVisible && <Page />}

// After
<Activity mode={isVisible ? 'visible' : 'hidden'}>
  <Page />
</Activity>

In React 19.2, Activity supports two modes: visible and hidden.

• hidden: hides the children, unmounts effects, and defers all updates until React has nothing left to work on.
• visible: shows the children, mounts effects, and allows updates to be processed normally.

This means you can pre-render and keep rendering hidden parts of the app without impacting the performance of anything visible on screen.

You can use Activity to render hidden parts of the app that a user is likely to navigate to next, or to save the state of parts the user navigates away from. This helps make navigations quicker by loading data, css, and images in the background, and allows back navigations to maintain state such as input fields.

In the future, we plan to add more modes to Activity for different use cases.

For examples on how to use Activity, check out the Activity docs.

React Performance Tracks

React 19.2 adds a new set of custom tracks to Chrome DevTools performance profiles to provide more information about the performance of your React app:

For more information, see the React Performance Tracks docs.

useEffectEvent

When using Effects you may want to read the most recent props or state inside an Effect without re-running the Effect when those values change. For example, in the following code the theme prop is used inside an Effect, but we don’t want the Effect to re-run when theme changes:

function ChatRoom({ roomId, theme }) {
  useEffect(() => {
    const connection = createConnection(serverUrl, roomId);
    connection.on('connected', () => {
      showNotification('Connected!', theme);
    });
    connection.connect();
    return () => {
      connection.disconnect()
    };
  }, [roomId, theme]);
  // ...

To solve this, most users just disable the lint rule and exclude the dependency. But that can lead to bugs since the linter can no longer help you keep the dependencies up to date if you need to update the Effect later.

React 19.2 introduces useEffectEvent, which lets you declare “Effect Events” that can be called inside Effects. Effect Events always access the latest values from props and state when they are invoked, so you can read the latest values without re-running the Effect:

With useEffectEvent, we can define the onConnected callback as an “Effect Event”. Now, it doesn’t re-run when the values change, but it can still “see” the latest values of your props and state:

function ChatRoom({ roomId, theme, threadId }) {
  const onConnected = useEffectEvent(() => {
    showNotification('Connected!', theme);
  });

  useEffect(() => {
    const connection = createConnection(serverUrl, roomId, threadId);
    connection.on('connected', () => {
      onConnected();
    });
    connection.connect();
    return () => connection.disconnect();
  }, [roomId, threadId]); // ✅ All dependencies declared
  // ...

For more information, see Separating Events from Effects and the useEffectEvent docs.

cacheSignal

cacheSignal allows you to know when the cache() lifetime is over:

import {cache, cacheSignal} from 'react';
const dedupedFetch = cache(fetch);

async function Component() {
  await dedupedFetch(url, { signal: cacheSignal() });
}

This allows you to clean up or abort work when the result will no longer be used in the cache, such as:

• React has successfully completed rendering
• The render was aborted
• The render has failed

For more info, see the cacheSignal docs.

Notable Changes

Batching Suspense Boundaries for SSR

We fixed a behavioral bug where Suspense boundaries would reveal differently depending on if they were rendered on the client or when streaming from server-side rendering.

Starting in 19.2, React will batch reveals of server-rendered Suspense boundaries for a short time, to allow more content to be revealed together and align with the client-rendered behavior.

This fix also prepares apps for supporting <ViewTransition> for Suspense during SSR. By revealing more content together, animations can run in larger batches of content, and avoid chaining animations of content that stream in close together.

SSR: Web Streams support for Node

React 19.2 adds support for Web Streams for streaming SSR in Node.js:

• renderToReadableStream is now available for Node.js
• prerender is now available for Node.js

Update the default useId prefix

In 19.2, we’re updating the default useId prefix from :r: (19.0.0) or «r» (19.1.0) to _r_.

The original intent of using a special character that was not valid for CSS selectors was that it would be unlikely to collide with IDs written by users. However, to support View Transitions, we need to ensure that IDs generated by useId are valid for view-transition-name and XML 1.0 names.

Changelog

Other notable changes

• react-dom: Allow nonce to be used on hoistable styles #32461
• react-dom: Warn for using a React owned node as a Container if it also has text content #32774

Notable bug fixes

• react: Stringify context as “SomeContext” instead of “SomeContext.Provider” #33507
• react: Fix infinite useDeferredValue loop in popstate event #32821
• react: Fix a bug when an initial value was passed to useDeferredValue #34376
• react: Fix a crash when submitting forms with Client Actions #33055
• react: Hide/unhide the content of dehydrated suspense boundaries if they resuspend #32900
• react: Avoid stack overflow on wide trees during Hot Reload #34145
• react: Improve component stacks in various places #33629, #33724, #32735, #33723
• react: Fix a bug with React.use inside React.lazy-ed Component #33941
• react-dom: Stop warning when ARIA 1.3 attributes are used #34264
• react-dom: Fix a bug with deeply nested Suspense inside Suspense fallbacks #33467
• react-dom: Avoid hanging when suspending after aborting while rendering #34192

For a full list of changes, please see the Changelog.

Thanks to everyone who helped review this post.