{title}
- {canary && (
+ {version === 'canary' && (
+ )}
+ {version === 'experimental' && (
+
)}
diff --git a/src/components/Seo.tsx b/src/components/Seo.tsx
index 628085744..b8a8394b6 100644
--- a/src/components/Seo.tsx
+++ b/src/components/Seo.tsx
@@ -124,7 +124,14 @@ export const Seo = withRouter(
)}
+
+
+### React Compiler is now in RC! {/*react-compiler-is-now-in-rc*/}
+
+Please see the [RC blog post](/blog/2025/04/21/react-compiler-rc) for details.
+
+
+
React チームより以下の最新情報を共有できることを嬉しく思います。
diff --git a/src/content/blog/2025/04/21/react-compiler-rc.md b/src/content/blog/2025/04/21/react-compiler-rc.md
new file mode 100644
index 000000000..ecbbb8747
--- /dev/null
+++ b/src/content/blog/2025/04/21/react-compiler-rc.md
@@ -0,0 +1,128 @@
+---
+title: "React Compiler RC"
+author: Lauren Tan and Mofei Zhang
+date: 2025/04/21
+description: We are releasing the compiler's first Release Candidate (RC) today.
+
+---
+
+April 21, 2025 by [Lauren Tan](https://x.com/potetotes) and [Mofei Zhang](https://x.com/zmofei).
+
+---
+
+
+
+The React team is excited to share new updates:
+
+
+
+1. We're publishing React Compiler RC today, in preparation of the compiler's stable release.
+2. We're merging `eslint-plugin-react-compiler` into `eslint-plugin-react-hooks`.
+3. We've added support for swc and are working with oxc to support Babel-free builds.
+
+---
+
+[React Compiler](https://react.dev/learn/react-compiler) is a build-time tool that optimizes your React app through automatic memoization. Last year, we published React Compiler’s [first beta](https://react.dev/blog/2024/10/21/react-compiler-beta-release) and received lots of great feedback and contributions. We’re excited about the wins we’ve seen from folks adopting the compiler (see case studies from [Sanity Studio](https://github.com/reactwg/react-compiler/discussions/33) and [Wakelet](https://github.com/reactwg/react-compiler/discussions/52)) and are working towards a stable release.
+
+We are releasing the compiler's first Release Candidate (RC) today. The RC is intended to be a stable and near-final version of the compiler, and safe to try out in production.
+
+## Use React Compiler RC today {/*use-react-compiler-rc-today*/}
+To install the RC:
+
+npm
+
+{`npm install --save-dev --save-exact babel-plugin-react-compiler@rc`}
+
+
+pnpm
+
+{`pnpm add --save-dev --save-exact babel-plugin-react-compiler@rc`}
+
+
+yarn
+
+{`yarn add --dev --exact babel-plugin-react-compiler@rc`}
+
+
+As part of the RC, we've been making React Compiler easier to add to your projects and added optimizations to how the compiler generates memoization. React Complier now supports optional chains and array indices as dependencies. We're exploring how to infer even more dependencies like equality checks and string interpolation. These improvements ultimately result in fewer re-renders and more responsive UIs.
+
+We have also heard from the community that the ref-in-render validation sometimes has false positives. Since as a general philosophy we want you to be able to fully trust in the compiler's error messages and hints, we are turning it off by default for now. We will keep working to improve this validation, and we will re-enable it in a follow up release.
+
+You can find more details on using the Compiler in [our docs](https://react.dev/learn/react-compiler).
+
+## Feedback {/*feedback*/}
+During the RC period, we encourage all React users to try the compiler and provide feedback in the React repo. Please [open an issue](https://github.com/facebook/react/issues) if you encounter any bugs or unexpected behavior. If you have a general question or suggestion, please post them in the [React Compiler Working Group](https://github.com/reactwg/react-compiler/discussions).
+
+## Backwards Compatibility {/*backwards-compatibility*/}
+As noted in the Beta announcement, React Compiler is compatible with React 17 and up. If you are not yet on React 19, you can use React Compiler by specifying a minimum target in your compiler config, and adding `react-compiler-runtime` as a dependency. You can find docs on this [here](https://react.dev/learn/react-compiler#using-react-compiler-with-react-17-or-18).
+
+## Migrating from eslint-plugin-react-compiler to eslint-plugin-react-hooks {/*migrating-from-eslint-plugin-react-compiler-to-eslint-plugin-react-hooks*/}
+If you have already installed eslint-plugin-react-compiler, you can now remove it and use `eslint-plugin-react-hooks@6.0.0-rc.1`. Many thanks to [@michaelfaith](https://bsky.app/profile/michael.faith) for contributing to this improvement!
+
+To install:
+
+npm
+
+{`npm install --save-dev eslint-plugin-react-hooks@6.0.0-rc.1`}
+
+
+pnpm
+
+{`pnpm add --save-dev eslint-plugin-react-hooks@6.0.0-rc.1`}
+
+
+yarn
+
+{`yarn add --dev eslint-plugin-react-hooks@6.0.0-rc.1`}
+
+
+```js
+// eslint.config.js
+import * as reactHooks from 'eslint-plugin-react-hooks';
+
+export default [
+ // Flat Config (eslint 9+)
+ reactHooks.configs.recommended,
+
+ // Legacy Config
+ reactHooks.configs['recommended-latest']
+];
+```
+
+To enable the React Compiler rule, add `'react-hooks/react-compiler': 'error'` to your ESLint configuration.
+
+The linter does not require the compiler to be installed, so there's no risk in upgrading eslint-plugin-react-hooks. We recommend everyone upgrade today.
+
+## swc support (experimental) {/*swc-support-experimental*/}
+React Compiler can be installed across [several build tools](/learn/react-compiler#installation) such as Babel, Vite, and Rsbuild.
+
+In addition to those tools, we have been collaborating with Kang Dongyoon ([@kdy1dev](https://x.com/kdy1dev)) from the [swc](https://swc.rs/) team on adding additional support for React Compiler as an swc plugin. While this work isn't done, Next.js build performance should now be considerably faster when the [React Compiler is enabled in your Next.js app](https://nextjs.org/docs/app/api-reference/config/next-config-js/reactCompiler).
+
+We recommend using Next.js [15.3.1](https://github.com/vercel/next.js/releases/tag/v15.3.1) or greater to get the best build performance.
+
+Vite users can continue to use [vite-plugin-react](https://github.com/vitejs/vite-plugin-react) to enable the compiler, by adding it as a [Babel plugin](https://react.dev/learn/react-compiler#usage-with-vite). We are also working with the [oxc](https://oxc.rs/) team to [add support for the compiler](https://github.com/oxc-project/oxc/issues/10048). Once [rolldown](https://github.com/rolldown/rolldown) is officially released and supported in Vite and oxc support is added for React Compiler, we'll update the docs with information on how to migrate.
+
+## Upgrading React Compiler {/*upgrading-react-compiler*/}
+React Compiler works best when the auto-memoization applied is strictly for performance. Future versions of the compiler may change how memoization is applied, for example it could become more granular and precise.
+
+However, because product code may sometimes break the [rules of React](https://react.dev/reference/rules) in ways that aren't always statically detectable in JavaScript, changing memoization can occasionally have unexpected results. For example, a previously memoized value might be used as a dependency for a useEffect somewhere in the component tree. Changing how or whether this value is memoized can cause over or under-firing of that useEffect. While we encourage [useEffect only for synchronization](https://react.dev/learn/synchronizing-with-effects), your codebase may have useEffects that cover other use-cases such as effects that needs to only run in response to specific values changing.
+
+In other words, changing memoization may under rare circumstances cause unexpected behavior. For this reason, we recommend following the Rules of React and employing continuous end-to-end testing of your app so you can upgrade the compiler with confidence and identify any rules of React violations that might cause issues.
+
+If you don't have good test coverage, we recommend pinning the compiler to an exact version (eg `19.1.0`) rather than a SemVer range (eg `^19.1.0`). You can do this by passing the `--save-exact` (npm/pnpm) or `--exact` flags (yarn) when upgrading the compiler. You should then do any upgrades of the compiler manually, taking care to check that your app still works as expected.
+
+## Roadmap to Stable {/*roadmap-to-stable*/}
+*This is not a final roadmap, and is subject to change.*
+
+After a period of final feedback from the community on the RC, we plan on a Stable Release for the compiler.
+
+* ✅ Experimental: Released at React Conf 2024, primarily for feedback from application developers.
+* ✅ Public Beta: Available today, for feedback from library authors.
+* ✅ Release Candidate (RC): React Compiler works for the majority of rule-following apps and libraries without issue.
+* General Availability: After final feedback period from the community.
+
+Post-Stable, we plan to add more compiler optimizations and improvements. This includes both continual improvements to automatic memoization, and new optimizations altogether, with minimal to no change of product code. Each upgrade will continue to improve performance and add better handling of diverse JavaScript and React patterns.
+
+---
+
+Thanks to [Joe Savona](https://x.com/en_JS), [Jason Bonta](https://x.com/someextent), [Jimmy Lai](https://x.com/feedthejim), and [Kang Dongyoon](https://x.com/kdy1dev) (@kdy1dev) for reviewing and editing this post.
diff --git a/src/content/blog/2025/04/23/react-labs-view-transitions-activity-and-more.md b/src/content/blog/2025/04/23/react-labs-view-transitions-activity-and-more.md
new file mode 100644
index 000000000..e4bb25a4a
--- /dev/null
+++ b/src/content/blog/2025/04/23/react-labs-view-transitions-activity-and-more.md
@@ -0,0 +1,14358 @@
+---
+title: "React Labs: View Transitions, Activity, and more"
+author: Ricky Hanlon
+date: 2025/04/23
+description: In React Labs posts, we write about projects in active research and development. In this post, we're sharing two new experimental features that are ready to try today, and updates on other areas we're working on now.
+---
+
+April 23, 2025 by [Ricky Hanlon](https://twitter.com/rickhanlonii)
+
+---
+
+
+
+In React Labs posts, we write about projects in active research and development. In this post, we're sharing two new experimental features that are ready to try today, and updates on other areas we're working on now.
+
+
+
+
+
+
+React Conf 2025 is scheduled for October 7–8 in Henderson, Nevada!
+
+We're looking for speakers to help us create talks about the features covered in this post. If you're interested in speaking at ReactConf, [please apply here](https://forms.reform.app/react-conf/call-for-speakers/) (no talk proposal required).
+
+For more info on tickets, free streaming, sponsoring, and more, see [the React Conf website](https://conf.react.dev).
+
+
+
+Today, we're excited to release documentation for two new experimental features that are ready for testing:
+
+- [View Transitions](#view-transitions)
+- [Activity](#activity)
+
+We're also sharing updates on new features currently in development:
+- [React Performance Tracks](#react-performance-tracks)
+- [Compiler IDE Extension](#compiler-ide-extension)
+- [Automatic Effect Dependencies](#automatic-effect-dependencies)
+- [Fragment Refs](#fragment-refs)
+- [Concurrent Stores](#concurrent-stores)
+
+---
+
+# New Experimental Features {/*new-experimental-features*/}
+
+View Transitions and Activity are now ready for testing in `react@experimental`. These features have been tested in production and are stable, but the final API may still change as we incorporate feedback.
+
+You can try them by upgrading React packages to the most recent experimental version:
+
+- `react@experimental`
+- `react-dom@experimental`
+
+Read on to learn how to use these features in your app, or check out the newly published docs:
+
+- [``](/reference/react/ViewTransition): A component that lets you activate an animation for a Transition.
+- [`addTransitionType`](/reference/react/addTransitionType): A function that allows you to specify the cause of a Transition.
+- [``](/reference/react/Activity): A component that lets you hide and show parts of the UI.
+
+## View Transitions {/*view-transitions*/}
+
+React View Transitions are a new experimental feature that makes it easier to add animations to UI transitions in your app. Under-the-hood, these animations use the new [`startViewTransition`](https://developer.mozilla.org/en-US/docs/Web/API/Document/startViewTransition) API available in most modern browsers.
+
+To opt-in to animating an element, wrap it in the new `` component:
+
+```js
+// "what" to animate.
+
+
animate me
+
+```
+
+This new component lets you declaratively define "what" to animate when an animation is activated.
+
+You can define "when" to animate by using one of these three triggers for a View Transition:
+
+```js
+// "when" to animate.
+
+// Transitions
+startTransition(() => setState(...));
+
+// Deferred Values
+const deferred = useDeferredValue(value);
+
+// Suspense
+}>
+
Loading...
+
+```
+
+By default, these animations use the [default CSS animations for View Transitions](https://developer.mozilla.org/en-US/docs/Web/API/View_Transition_API/Using#customizing_your_animations) applied (typically a smooth cross-fade). You can use [view transition pseudo-selectors](https://developer.mozilla.org/en-US/docs/Web/API/View_Transition_API/Using#the_view_transition_pseudo-element_tree) to define "how" the animation runs. For example, you can use `*` to change the default animation for all transitions:
+
+```
+// "how" to animate.
+::view-transition-old(*) {
+ animation: 300ms ease-out fade-out;
+}
+::view-transition-new(*) {
+ animation: 300ms ease-in fade-in;
+}
+```
+
+When the DOM updates due to an animation trigger—like `startTransition`, `useDeferredValue`, or a `Suspense` fallback switching to content—React will use [declarative heuristics](/reference/react/ViewTransition#viewtransition) to automatically determine which `` components to activate for the animation. The browser will then run the animation that's defined in CSS.
+
+If you're familiar with the browser's View Transition API and want to know how React supports it, check out [How does `` Work](/reference/react/ViewTransition#how-does-viewtransition-work) in the docs.
+
+In this post, let's take a look at a few examples of how to use View Transitions.
+
+We'll start with this app, which doesn't animate any of the following interactions:
+- Click a video to view the details.
+- Click "back" to go back to the feed.
+- Type in the list to filter the videos.
+
+
+
+```js src/App.js active
+import TalkDetails from './Details'; import Home from './Home'; import {useRouter} from './router';
+
+export default function App() {
+ const {url} = useRouter();
+
+ // 🚩This version doesn't include any animations yet
+ return url === '/' ? : ;
+}
+```
+
+```js src/Details.js
+import { fetchVideo, fetchVideoDetails } from "./data";
+import { Thumbnail, VideoControls } from "./Videos";
+import { useRouter } from "./router";
+import Layout from "./Layout";
+import { use, Suspense } from "react";
+import { ChevronLeft } from "./Icons";
+
+function VideoInfo({ id }) {
+ const details = use(fetchVideoDetails(id));
+ return (
+ <>
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js active
+import { useState, unstable_ViewTransition as ViewTransition } from "react"; import LikeButton from "./LikeButton"; import { useRouter } from "./router"; import { PauseIcon, PlayIcon } from "./Icons"; import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+
+ );
+}
+
+```
+
+```js src/Icons.js hidden
+export function ChevronLeft() {
+ return (
+
+ );
+}
+
+export function PauseIcon() {
+ return (
+
+ );
+}
+
+export function PlayIcon() {
+ return (
+
+ );
+}
+export function Heart({liked, animate}) {
+ return (
+ <>
+
+
+
+
+ );
+}
+
+export function IconSearch(props) {
+ return (
+
+ );
+}
+```
+
+```js src/Layout.js active
+import {unstable_ViewTransition as ViewTransition} from 'react'; import { useIsNavPending } from "./router";
+
+export default function Page({ heading, children }) {
+ const isPending = useIsNavPending();
+ return (
+
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js
+import { useState, unstable_ViewTransition as ViewTransition } from "react"; import LikeButton from "./LikeButton"; import { useRouter } from "./router"; import { PauseIcon, PlayIcon } from "./Icons"; import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ {/* Custom classes based on transition type. */}
+
+ {heading}
+
+ {isPending && }
+
+
+ {/* Opt-out of ViewTransition for the content. */}
+ {/* Content can define it's own ViewTransition. */}
+
+
+
{children}
+
+
+
+ );
+}
+```
+
+```js src/LikeButton.js hidden
+import {useState} from 'react';
+import {Heart} from './Icons';
+
+// A hack since we don't actually have a backend.
+// Unlike local state, this survives videos being filtered.
+const likedVideos = new Set();
+
+export default function LikeButton({video}) {
+ const [isLiked, setIsLiked] = useState(() => likedVideos.has(video.id));
+ const [animate, setAnimate] = useState(false);
+ return (
+
+ );
+}
+```
+
+```js src/Videos.js hidden
+import { useState, unstable_ViewTransition as ViewTransition } from "react";
+import LikeButton from "./LikeButton";
+import { useRouter } from "./router";
+import { PauseIcon, PlayIcon } from "./Icons";
+import { startTransition } from "react";
+
+export function Thumbnail({ video, children }) {
+ // Add a name to animate with a shared element transition.
+ // This uses the default animation, no additional css needed.
+ return (
+
+
+ );
+}
+```
+
+
+```js src/data.js hidden
+const videos = [
+ {
+ id: '1',
+ title: 'First video',
+ description: 'Video description',
+ image: 'blue',
+ },
+ {
+ id: '2',
+ title: 'Second video',
+ description: 'Video description',
+ image: 'red',
+ },
+ {
+ id: '3',
+ title: 'Third video',
+ description: 'Video description',
+ image: 'green',
+ },
+ {
+ id: '4',
+ title: 'Fourth video',
+ description: 'Video description',
+ image: 'purple',
+ },
+ {
+ id: '5',
+ title: 'Fifth video',
+ description: 'Video description',
+ image: 'yellow',
+ },
+ {
+ id: '6',
+ title: 'Sixth video',
+ description: 'Video description',
+ image: 'gray',
+ },
+];
+
+let videosCache = new Map();
+let videoCache = new Map();
+let videoDetailsCache = new Map();
+const VIDEO_DELAY = 1;
+const VIDEO_DETAILS_DELAY = 1000;
+export function fetchVideos() {
+ if (videosCache.has(0)) {
+ return videosCache.get(0);
+ }
+ const promise = new Promise((resolve) => {
+ setTimeout(() => {
+ resolve(videos);
+ }, VIDEO_DELAY);
+ });
+ videosCache.set(0, promise);
+ return promise;
+}
+
+export function fetchVideo(id) {
+ if (videoCache.has(id)) {
+ return videoCache.get(id);
+ }
+ const promise = new Promise((resolve) => {
+ setTimeout(() => {
+ resolve(videos.find((video) => video.id === id));
+ }, VIDEO_DELAY);
+ });
+ videoCache.set(id, promise);
+ return promise;
+}
+
+export function fetchVideoDetails(id) {
+ if (videoDetailsCache.has(id)) {
+ return videoDetailsCache.get(id);
+ }
+ const promise = new Promise((resolve) => {
+ setTimeout(() => {
+ resolve(videos.find((video) => video.id === id));
+ }, VIDEO_DETAILS_DELAY);
+ });
+ videoDetailsCache.set(id, promise);
+ return promise;
+}
+```
+
+```js src/router.js hidden
+import {useState, createContext, use, useTransition, useLayoutEffect, useEffect, unstable_addTransitionType as addTransitionType} from "react";
+
+export function Router({ children }) {
+ const [isPending, startTransition] = useTransition();
+ const [routerState, setRouterState] = useState({pendingNav: () => {}, url: document.location.pathname});
+ function navigate(url) {
+ startTransition(() => {
+ // Transition type for the cause "nav forward"
+ addTransitionType('nav-forward');
+ go(url);
+ });
+ }
+ function navigateBack(url) {
+ startTransition(() => {
+ // Transition type for the cause "nav backward"
+ addTransitionType('nav-back');
+ go(url);
+ });
+ }
+
+ function go(url) {
+ setRouterState({
+ url,
+ pendingNav() {
+ window.history.pushState({}, "", url);
+ },
+ });
+ }
+
+ useEffect(() => {
+ function handlePopState() {
+ // This should not animate because restoration has to be synchronous.
+ // Even though it's a transition.
+ startTransition(() => {
+ setRouterState({
+ url: document.location.pathname + document.location.search,
+ pendingNav() {
+ // Noop. URL has already updated.
+ },
+ });
+ });
+ }
+ window.addEventListener("popstate", handlePopState);
+ return () => {
+ window.removeEventListener("popstate", handlePopState);
+ };
+ }, []);
+ const pendingNav = routerState.pendingNav;
+ useLayoutEffect(() => {
+ pendingNav();
+ }, [pendingNav]);
+
+ return (
+
+ {children}
+
+ );
+}
+
+const RouterContext = createContext({ url: "/", params: {} });
+
+export function useRouter() {
+ return use(RouterContext);
+}
+
+export function useIsNavPending() {
+ return use(RouterContext).isPending;
+}
+
+```
+
+```css src/styles.css hidden
+@font-face {
+ font-family: Optimistic Text;
+ src: url(https://react.dev/fonts/Optimistic_Text_W_Rg.woff2) format("woff2");
+ font-weight: 400;
+ font-style: normal;
+ font-display: swap;
+}
+
+@font-face {
+ font-family: Optimistic Text;
+ src: url(https://react.dev/fonts/Optimistic_Text_W_Md.woff2) format("woff2");
+ font-weight: 500;
+ font-style: normal;
+ font-display: swap;
+}
+
+@font-face {
+ font-family: Optimistic Text;
+ src: url(https://react.dev/fonts/Optimistic_Text_W_Bd.woff2) format("woff2");
+ font-weight: 600;
+ font-style: normal;
+ font-display: swap;
+}
+
+@font-face {
+ font-family: Optimistic Text;
+ src: url(https://react.dev/fonts/Optimistic_Text_W_Bd.woff2) format("woff2");
+ font-weight: 700;
+ font-style: normal;
+ font-display: swap;
+}
+
+* {
+ box-sizing: border-box;
+}
+
+html {
+ background-image: url(https://react.dev/images/meta-gradient-dark.png);
+ background-size: 100%;
+ background-position: -100%;
+ background-color: rgb(64 71 86);
+ background-repeat: no-repeat;
+ height: 100%;
+ width: 100%;
+}
+
+body {
+ font-family: Optimistic Text, -apple-system, ui-sans-serif, system-ui, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol, Noto Color Emoji;
+ padding: 10px 0 10px 0;
+ margin: 0;
+ display: flex;
+ justify-content: center;
+}
+
+#root {
+ flex: 1 1;
+ height: auto;
+ background-color: #fff;
+ border-radius: 10px;
+ max-width: 450px;
+ min-height: 600px;
+ padding-bottom: 10px;
+}
+
+h1 {
+ margin-top: 0;
+ font-size: 22px;
+}
+
+h2 {
+ margin-top: 0;
+ font-size: 20px;
+}
+
+h3 {
+ margin-top: 0;
+ font-size: 18px;
+}
+
+h4 {
+ margin-top: 0;
+ font-size: 16px;
+}
+
+h5 {
+ margin-top: 0;
+ font-size: 14px;
+}
+
+h6 {
+ margin-top: 0;
+ font-size: 12px;
+}
+
+code {
+ font-size: 1.2em;
+}
+
+ul {
+ padding-inline-start: 20px;
+}
+
+.sr-only {
+ position: absolute;
+ width: 1px;
+ height: 1px;
+ padding: 0;
+ margin: -1px;
+ overflow: hidden;
+ clip: rect(0, 0, 0, 0);
+ white-space: nowrap;
+ border-width: 0;
+}
+
+.absolute {
+ position: absolute;
+}
+
+.overflow-visible {
+ overflow: visible;
+}
+
+.visible {
+ overflow: visible;
+}
+
+.fit {
+ width: fit-content;
+}
+
+
+/* Layout */
+.page {
+ display: flex;
+ flex-direction: column;
+ height: 100%;
+}
+
+.top-hero {
+ height: 200px;
+ display: flex;
+ justify-content: center;
+ align-items: center;
+ background-image: conic-gradient(
+ from 90deg at -10% 100%,
+ #2b303b 0deg,
+ #2b303b 90deg,
+ #16181d 1turn
+ );
+}
+
+.bottom {
+ flex: 1;
+ overflow: auto;
+}
+
+.top-nav {
+ display: flex;
+ align-items: center;
+ justify-content: space-between;
+ margin-bottom: 0;
+ padding: 0 12px;
+ top: 0;
+ width: 100%;
+ height: 44px;
+ color: #23272f;
+ font-weight: 700;
+ font-size: 20px;
+ z-index: 100;
+ cursor: default;
+}
+
+.content {
+ padding: 0 12px;
+ margin-top: 4px;
+}
+
+
+.loader {
+ color: #23272f;
+ font-size: 3px;
+ width: 1em;
+ margin-right: 18px;
+ height: 1em;
+ border-radius: 50%;
+ position: relative;
+ text-indent: -9999em;
+ animation: loading-spinner 1.3s infinite linear;
+ animation-delay: 200ms;
+ transform: translateZ(0);
+}
+
+@keyframes loading-spinner {
+ 0%,
+ 100% {
+ box-shadow: 0 -3em 0 0.2em,
+ 2em -2em 0 0em, 3em 0 0 -1em,
+ 2em 2em 0 -1em, 0 3em 0 -1em,
+ -2em 2em 0 -1em, -3em 0 0 -1em,
+ -2em -2em 0 0;
+ }
+ 12.5% {
+ box-shadow: 0 -3em 0 0, 2em -2em 0 0.2em,
+ 3em 0 0 0, 2em 2em 0 -1em, 0 3em 0 -1em,
+ -2em 2em 0 -1em, -3em 0 0 -1em,
+ -2em -2em 0 -1em;
+ }
+ 25% {
+ box-shadow: 0 -3em 0 -0.5em,
+ 2em -2em 0 0, 3em 0 0 0.2em,
+ 2em 2em 0 0, 0 3em 0 -1em,
+ -2em 2em 0 -1em, -3em 0 0 -1em,
+ -2em -2em 0 -1em;
+ }
+ 37.5% {
+ box-shadow: 0 -3em 0 -1em, 2em -2em 0 -1em,
+ 3em 0em 0 0, 2em 2em 0 0.2em, 0 3em 0 0em,
+ -2em 2em 0 -1em, -3em 0em 0 -1em, -2em -2em 0 -1em;
+ }
+ 50% {
+ box-shadow: 0 -3em 0 -1em, 2em -2em 0 -1em,
+ 3em 0 0 -1em, 2em 2em 0 0em, 0 3em 0 0.2em,
+ -2em 2em 0 0, -3em 0em 0 -1em, -2em -2em 0 -1em;
+ }
+ 62.5% {
+ box-shadow: 0 -3em 0 -1em, 2em -2em 0 -1em,
+ 3em 0 0 -1em, 2em 2em 0 -1em, 0 3em 0 0,
+ -2em 2em 0 0.2em, -3em 0 0 0, -2em -2em 0 -1em;
+ }
+ 75% {
+ box-shadow: 0em -3em 0 -1em, 2em -2em 0 -1em,
+ 3em 0em 0 -1em, 2em 2em 0 -1em, 0 3em 0 -1em,
+ -2em 2em 0 0, -3em 0em 0 0.2em, -2em -2em 0 0;
+ }
+ 87.5% {
+ box-shadow: 0em -3em 0 0, 2em -2em 0 -1em,
+ 3em 0 0 -1em, 2em 2em 0 -1em, 0 3em 0 -1em,
+ -2em 2em 0 0, -3em 0em 0 0, -2em -2em 0 0.2em;
+ }
+}
+
+/* LikeButton */
+.like-button {
+ outline-offset: 2px;
+ position: relative;
+ display: flex;
+ align-items: center;
+ justify-content: center;
+ width: 2.5rem;
+ height: 2.5rem;
+ cursor: pointer;
+ border-radius: 9999px;
+ border: none;
+ outline: none 2px;
+ color: #5e687e;
+ background: none;
+}
+
+.like-button:focus {
+ color: #a6423a;
+ background-color: rgba(166, 66, 58, .05);
+}
+
+.like-button:active {
+ color: #a6423a;
+ background-color: rgba(166, 66, 58, .05);
+ transform: scaleX(0.95) scaleY(0.95);
+}
+
+.like-button:hover {
+ background-color: #f6f7f9;
+}
+
+.like-button.liked {
+ color: #a6423a;
+}
+
+/* Icons */
+@keyframes circle {
+ 0% {
+ transform: scale(0);
+ stroke-width: 16px;
+ }
+
+ 50% {
+ transform: scale(.5);
+ stroke-width: 16px;
+ }
+
+ to {
+ transform: scale(1);
+ stroke-width: 0;
+ }
+}
+
+.circle {
+ color: rgba(166, 66, 58, .5);
+ transform-origin: center;
+ transition-property: all;
+ transition-duration: .15s;
+ transition-timing-function: cubic-bezier(.4,0,.2,1);
+}
+
+.circle.liked.animate {
+ animation: circle .3s forwards;
+}
+
+.heart {
+ width: 1.5rem;
+ height: 1.5rem;
+}
+
+.heart.liked {
+ transform-origin: center;
+ transition-property: all;
+ transition-duration: .15s;
+ transition-timing-function: cubic-bezier(.4, 0, .2, 1);
+}
+
+.heart.liked.animate {
+ animation: scale .35s ease-in-out forwards;
+}
+
+.control-icon {
+ color: hsla(0, 0%, 100%, .5);
+ filter: drop-shadow(0 20px 13px rgba(0, 0, 0, .03)) drop-shadow(0 8px 5px rgba(0, 0, 0, .08));
+}
+
+.chevron-left {
+ margin-top: 2px;
+ rotate: 90deg;
+}
+
+
+/* Video */
+.thumbnail {
+ position: relative;
+ aspect-ratio: 16 / 9;
+ display: flex;
+ overflow: hidden;
+ flex-direction: column;
+ justify-content: center;
+ align-items: center;
+ border-radius: 0.5rem;
+ outline-offset: 2px;
+ width: 8rem;
+ vertical-align: middle;
+ background-color: #ffffff;
+ background-size: cover;
+ user-select: none;
+}
+
+.thumbnail.blue {
+ background-image: conic-gradient(at top right, #c76a15, #087ea4, #2b3491);
+}
+
+.thumbnail.red {
+ background-image: conic-gradient(at top right, #c76a15, #a6423a, #2b3491);
+}
+
+.thumbnail.green {
+ background-image: conic-gradient(at top right, #c76a15, #388f7f, #2b3491);
+}
+
+.thumbnail.purple {
+ background-image: conic-gradient(at top right, #c76a15, #575fb7, #2b3491);
+}
+
+.thumbnail.yellow {
+ background-image: conic-gradient(at top right, #c76a15, #FABD62, #2b3491);
+}
+
+.thumbnail.gray {
+ background-image: conic-gradient(at top right, #c76a15, #4E5769, #2b3491);
+}
+
+.video {
+ display: flex;
+ flex-direction: row;
+ gap: 0.75rem;
+ align-items: center;
+}
+
+.video .link {
+ display: flex;
+ flex-direction: row;
+ flex: 1 1 0;
+ gap: 0.125rem;
+ outline-offset: 4px;
+ cursor: pointer;
+}
+
+.video .info {
+ display: flex;
+ flex-direction: column;
+ justify-content: center;
+ margin-left: 8px;
+ gap: 0.125rem;
+}
+
+.video .info:hover {
+ text-decoration: underline;
+}
+
+.video-title {
+ font-size: 15px;
+ line-height: 1.25;
+ font-weight: 700;
+ color: #23272f;
+}
+
+.video-description {
+ color: #5e687e;
+ font-size: 13px;
+}
+
+/* Details */
+.details .thumbnail {
+ position: relative;
+ aspect-ratio: 16 / 9;
+ display: flex;
+ overflow: hidden;
+ flex-direction: column;
+ justify-content: center;
+ align-items: center;
+ border-radius: 0.5rem;
+ outline-offset: 2px;
+ width: 100%;
+ vertical-align: middle;
+ background-color: #ffffff;
+ background-size: cover;
+ user-select: none;
+}
+
+.video-details-title {
+ margin-top: 8px;
+}
+
+.video-details-speaker {
+ display: flex;
+ gap: 8px;
+ margin-top: 10px
+}
+
+.back {
+ display: flex;
+ align-items: center;
+ margin-left: -5px;
+ cursor: pointer;
+}
+
+.back:hover {
+ text-decoration: underline;
+}
+
+.info-title {
+ font-size: 1.5rem;
+ font-weight: 700;
+ line-height: 1.25;
+ margin: 8px 0 0 0 ;
+}
+
+.info-description {
+ margin: 8px 0 0 0;
+}
+
+.controls {
+ cursor: pointer;
+}
+
+.fallback {
+ background: #f6f7f8 linear-gradient(to right, #e6e6e6 5%, #cccccc 25%, #e6e6e6 35%) no-repeat;
+ background-size: 800px 104px;
+ display: block;
+ line-height: 1.25;
+ margin: 8px 0 0 0;
+ border-radius: 5px;
+ overflow: hidden;
+
+ animation: 1s linear 1s infinite shimmer;
+ animation-delay: 300ms;
+ animation-duration: 1s;
+ animation-fill-mode: forwards;
+ animation-iteration-count: infinite;
+ animation-name: shimmer;
+ animation-timing-function: linear;
+}
+
+
+.fallback.title {
+ width: 130px;
+ height: 30px;
+
+}
+
+.fallback.description {
+ width: 150px;
+ height: 21px;
+}
+
+@keyframes shimmer {
+ 0% {
+ background-position: -468px 0;
+ }
+
+ 100% {
+ background-position: 468px 0;
+ }
+}
+
+.search {
+ margin-bottom: 10px;
+}
+.search-input {
+ width: 100%;
+ position: relative;
+}
+
+.search-icon {
+ position: absolute;
+ top: 0;
+ bottom: 0;
+ inset-inline-start: 0;
+ display: flex;
+ align-items: center;
+ padding-inline-start: 1rem;
+ pointer-events: none;
+ color: #99a1b3;
+}
+
+.search-input input {
+ display: flex;
+ padding-inline-start: 2.75rem;
+ padding-top: 10px;
+ padding-bottom: 10px;
+ width: 100%;
+ text-align: start;
+ background-color: rgb(235 236 240);
+ outline: 2px solid transparent;
+ cursor: pointer;
+ border: none;
+ align-items: center;
+ color: rgb(35 39 47);
+ border-radius: 9999px;
+ vertical-align: middle;
+ font-size: 15px;
+}
+
+.search-input input:hover, .search-input input:active {
+ background-color: rgb(235 236 240/ 0.8);
+ color: rgb(35 39 47/ 0.8);
+}
+
+/* Home */
+.video-list {
+ position: relative;
+}
+
+.video-list .videos {
+ display: flex;
+ flex-direction: column;
+ gap: 1rem;
+ overflow-y: auto;
+ height: 100%;
+}
+```
+
+
+```css src/animations.css
+/* No additional animations needed */
+
+
+
+
+
+
+
+
+
+/* Previously defined animations below */
+
+
+
+
+
+
+/* Slide animations for Suspense the fallback down */
+::view-transition-old(.slide-down) {
+ animation: 150ms ease-out both fade-out, 150ms ease-out both slide-down;
+}
+
+::view-transition-new(.slide-up) {
+ animation: 210ms ease-in 150ms both fade-in, 400ms ease-in both slide-up;
+}
+
+/* Animations for view transition classed added by transition type */
+::view-transition-old(.slide-forward) {
+ /* when sliding forward, the "old" page should slide out to left. */
+ animation: 150ms cubic-bezier(0.4, 0, 1, 1) both fade-out,
+ 400ms cubic-bezier(0.4, 0, 0.2, 1) both slide-to-left;
+}
+
+::view-transition-new(.slide-forward) {
+ /* when sliding forward, the "new" page should slide in from right. */
+ animation: 210ms cubic-bezier(0, 0, 0.2, 1) 150ms both fade-in,
+ 400ms cubic-bezier(0.4, 0, 0.2, 1) both slide-from-right;
+}
+
+::view-transition-old(.slide-back) {
+ /* when sliding back, the "old" page should slide out to right. */
+ animation: 150ms cubic-bezier(0.4, 0, 1, 1) both fade-out,
+ 400ms cubic-bezier(0.4, 0, 0.2, 1) both slide-to-right;
+}
+
+::view-transition-new(.slide-back) {
+ /* when sliding back, the "new" page should slide in from left. */
+ animation: 210ms cubic-bezier(0, 0, 0.2, 1) 150ms both fade-in,
+ 400ms cubic-bezier(0.4, 0, 0.2, 1) both slide-from-left;
+}
+
+/* Keyframes to support our animations above. */
+@keyframes slide-up {
+ from {
+ transform: translateY(10px);
+ }
+ to {
+ transform: translateY(0);
+ }
+}
+
+@keyframes slide-down {
+ from {
+ transform: translateY(0);
+ }
+ to {
+ transform: translateY(10px);
+ }
+}
+
+@keyframes fade-in {
+ from {
+ opacity: 0;
+ }
+}
+
+@keyframes fade-out {
+ to {
+ opacity: 0;
+ }
+}
+
+@keyframes slide-to-right {
+ to {
+ transform: translateX(50px);
+ }
+}
+
+@keyframes slide-from-right {
+ from {
+ transform: translateX(50px);
+ }
+ to {
+ transform: translateX(0);
+ }
+}
+
+@keyframes slide-to-left {
+ to {
+ transform: translateX(-50px);
+ }
+}
+
+@keyframes slide-from-left {
+ from {
+ transform: translateX(-50px);
+ }
+ to {
+ transform: translateX(0);
+ }
+}
+
+/* Default .slow-fade. */
+::view-transition-old(.slow-fade) {
+ animation-duration: 500ms;
+}
+
+::view-transition-new(.slow-fade) {
+ animation-duration: 500ms;
+}
+```
+
+```js src/index.js hidden
+import React, {StrictMode} from 'react';
+import {createRoot} from 'react-dom/client';
+import './styles.css';
+import './animations.css';
+
+import App from './App';
+import {Router} from './router';
+
+const root = createRoot(document.getElementById('root'));
+root.render(
+
+
+
+
+
+);
+```
+
+```json package.json hidden
+{
+ "dependencies": {
+ "react": "experimental",
+ "react-dom": "experimental",
+ "react-scripts": "latest"
+ },
+ "scripts": {
+ "start": "react-scripts start",
+ "build": "react-scripts build",
+ "test": "react-scripts test --env=jsdom",
+ "eject": "react-scripts eject"
+ }
+}
+```
+
+
+
+### Server-Side Rendering with Activity {/*server-side-rendering-with-activity*/}
+
+When using Activity on a page that uses server-side rendering (SSR), there are additional optimizations.
+
+If part of the page is rendered with `mode="hidden"`, then it will not be included in the SSR response. Instead, React will schedule a client render for the content inside Activity while the rest of the page hydrates, prioritizing the visible content on screen.
+
+For parts of the UI rendered with `mode="visible"`, React will de-prioritize hydration of content within Activity, similar to how Suspense content is hydrated at a lower priority. If the user interacts with the page, we'll prioritize hydration within the boundary if needed.
+
+These are advanced use cases, but they show the additional benefits considered with Activity.
+
+### Future modes for Activity {/*future-modes-for-activity*/}
+
+In the future, we may add more modes to Activity.
+
+For example, a common use case is rendering a modal, where the previous "inactive" page is visible behind the "active" modal view. The "hidden" mode does not work for this use case because it's not visible and not included in SSR.
+
+Instead, we're considering a new mode that would keep the content visible—and included in SSR—but keep it unmounted and de-prioritize updates. This mode may also need to "pause" DOM updates, since it can be distracting to see backgrounded content updating while a modal is open.
+
+Another mode we're considering for Activity is the ability to automatically destroy state for hidden Activities if there is too much memory being used. Since the component is already unmounted, it may be preferable to destroy state for the least recently used hidden parts of the app rather than consume too many resources.
+
+These are areas we're still exploring, and we'll share more as we make progress. For more information on what Activity includes today, [check out the docs](/reference/react/Activity).
+
+---
+
+# Features in development {/*features-in-development*/}
+
+We're also developing features to help solve the common problems below.
+
+As we iterate on possible solutions, you may see some potential APIs we're testing being shared based on the PRs we are landing. Please keep in mind that as we try different ideas, we often change or remove different solutions after trying them out.
+
+When the solutions we're working on are shared too early, it can create churn and confusion in the community. To balance being transparent and limiting confusion, we're sharing the problems we're currently developing solutions for, without sharing a particular solution we have in mind.
+
+As these features progress, we'll announce them on the blog with docs included so you can try them out.
+
+## React Performance Tracks {/*react-performance-tracks*/}
+
+We're working on a new set of custom tracks to performance profilers using browser APIs that [allow adding custom tracks](https://developer.chrome.com/docs/devtools/performance/extension) to provide more information about the performance of your React app.
+
+This feature is still in progress, so we're not ready to publish docs to fully release it as an experimental feature yet. You can get a sneak preview when using an experimental version of React, which will automatically add the performance tracks to profiles:
+
+
+
+
+
+
+
+
+
+
+
+
+There are a few known issues we plan to address such as performance, and the scheduler track not always "connecting" work across Suspended trees, so it's not quite ready to try. We're also still collecting feedback from early adopters to improve the design and usability of the tracks.
+
+Once we solve those issues, we'll publish experimental docs and share that it's ready to try.
+
+---
+
+## Automatic Effect Dependencies {/*automatic-effect-dependencies*/}
+
+When we released hooks, we had three motivations:
+
+- **Sharing code between components**: hooks replaced patterns like render props and higher-order components to allow you to reuse stateful logic without changing your component hierarchy.
+- **Think in terms of function, not lifecycles**: hooks let you split one component into smaller functions based on what pieces are related (such as setting up a subscription or fetching data), rather than forcing a split based on lifecycle methods.
+- **Support ahead-of-time compilation**: hooks were designed to support ahead-of-time compilation with less pitfalls causing unintentional de-optimizations caused by lifecycle methods, and limitations of classes.
+
+Since their release, hooks have been successful at *sharing code between components*. Hooks are now the favored way to share logic between components, and there are less use cases for render props and higher order components. Hooks have also been successful at supporting features like Fast Refresh that were not possible with class components.
+
+### Effects can be hard {/*effects-can-be-hard*/}
+
+Unfortunately, some hooks are still hard to think in terms of function instead of lifecycles. Effects specifically are still hard to understand and are the most common pain point we hear from developers. Last year, we spent a significant amount of time researching how Effects were used, and how those use cases could be simplified and easier to understand.
+
+We found that often, the confusion is from using an Effect when you don't need to. The [You Might Not Need an Effect](/learn/you-might-not-need-an-effect) guide covers many cases for when Effects are not the right solution. However, even when an Effect is the right fit for a problem, Effects can still be harder to understand than class component lifecycles.
+
+We believe one of the reasons for confusion is that developers to think of Effects from the _component's_ perspective (like a lifecycle), instead of the _Effects_ point of view (what the Effect does).
+
+Let's look at an example [from the docs](/learn/lifecycle-of-reactive-effects#thinking-from-the-effects-perspective):
+
+```js
+useEffect(() => {
+ // Your Effect connected to the room specified with roomId...
+ const connection = createConnection(serverUrl, roomId);
+ connection.connect();
+ return () => {
+ // ...until it disconnected
+ connection.disconnect();
+ };
+}, [roomId]);
+```
+
+Many users would read this code as "on mount, connect to the roomId. whenever `roomId` changes, disconnect to the old room and re-create the connection". However, this is thinking from the component's lifecycle perspective, which means you will need to think of every component lifecycle state to write the Effect correctly. This can be difficult, so it's understandable that Effects seem harder than class lifecycles when using the component perspective.
+
+### Effects without dependencies {/*effects-without-dependencies*/}
+
+Instead, it's better to think from the Effect's perspective. The Effect doesn't know about the component lifecycles. It only describes how to start synchronization and how to stop it. When users think of Effects in this way, their Effects tend to be easier to write, and more resilient to being started and stopped as many times as is needed.
+
+We spent some time researching why Effects are thought of from the component perspective, and we think one of the reasons is the dependency array. Since you have to write it, it's right there and in your face reminding you of what you're "reacting" to and baiting you into the mental model of 'do this when these values change'.
+
+When we released hooks, we knew we could make them easier to use with ahead-of-time compilation. With the React Compiler, you're now able to avoid writing `useCallback` and `useMemo` yourself in most cases. For Effects, the compiler can insert the dependencies for you:
+
+```js
+useEffect(() => {
+ const connection = createConnection(serverUrl, roomId);
+ connection.connect();
+ return () => {
+ connection.disconnect();
+ };
+}); // compiler inserted dependencies.
+```
+
+With this code, the React Compiler can infer the dependencies for you and insert them automatically so you don't need to see or write them. With features like [the IDE extension](#compiler-ide-extension) and [`useEffectEvent`](/reference/react/experimental_useEffectEvent), we can provide a CodeLens to show you what the Compiler inserted for times you need to debug, or to optimize by removing a dependency. This helps reinforce the correct mental model for writing Effects, which can run at any time to synchronize your component or hook's state with something else.
+
+Our hope is that automatically inserting dependencies is not only easier to write, but that it also makes them easier to understand by forcing you to think in terms of what the Effect does, and not in component lifecycles.
+
+---
+
+## Compiler IDE Extension {/*compiler-ide-extension*/}
+
+Earlier this week [we shared](/blog/2025/04/21/react-compiler-rc) the React Compiler release candidate, and we're working towards shipping the first SemVer stable version of the compiler in the coming months.
+
+We've also begun exploring ways to use the React Compiler to provide information that can improve understanding and debugging your code. One idea we've started exploring is a new experimental LSP-based React IDE extension powered by React Compiler, similar to the extension used in [Lauren Tan's React Conf talk](https://conf2024.react.dev/talks/5).
+
+Our idea is that we can use the compiler's static analysis to provide more information, suggestions, and optimization opportunities directly in your IDE. For example, we can provide diagnostics for code breaking the Rules of React, hovers to show if components and hooks were optimized by the compiler, or a CodeLens to see [automatically inserted Effect dependencies](#automatic-effect-dependencies).
+
+The IDE extension is still an early exploration, but we'll share our progress in future updates.
+
+---
+
+## Fragment Refs {/*fragment-refs*/}
+
+Many DOM APIs like those for event management, positioning, and focus are difficult to compose when writing with React. This often leads developers to reach for Effects, managing multiple Refs, by using APIs like `findDOMNode` (removed in React 19).
+
+We are exploring adding refs to Fragments that would point to a group of DOM elements, rather than just a single element. Our hope is that this will simplify managing multiple children and make it easier to write composable React code when calling DOM APIs.
+
+Fragment refs are still being researched. We'll share more when we're closer to having the final API finished.
+
+---
+
+## Gesture Animations {/*gesture-animations*/}
+
+We're also researching ways to enhance View Transitions to support gesture animations such as swiping to open a menu, or scroll through a photo carousel.
+
+Gestures present new challenges for a few reasons:
+
+- **Gestures are continuous**: as you swipe the animation is tied to your finger placement time, rather than triggering and running to completion.
+- **Gestures don't complete**: when you release your finger gesture animations can run to completion, or revert to their original state (like when you only partially open a menu) depending on how far you go.
+- **Gestures invert old and new**: while you're animating, you want the page you are animating from to stay "alive" and interactive. This inverts the browser View Transition model where the "old" state is a snapshot and the "new" state is the live DOM.
+
+We believe we’ve found an approach that works well and may introduce a new API for triggering gesture transitions. For now, we're focused on shipping ``, and will revisit gestures afterward.
+
+---
+
+## Concurrent Stores {/*concurrent-stores*/}
+
+When we released React 18 with concurrent rendering, we also released `useSyncExternalStore` so external store libraries that did not use React state or context could [support concurrent rendering](https://github.com/reactwg/react-18/discussions/70) by forcing a synchronous render when the store is updated.
+
+Using `useSyncExternalStore` comes at a cost though, since it forces a bail out from concurrent features like transitions, and forces existing content to show Suspense fallbacks.
+
+Now that React 19 has shipped, we're revisiting this problem space to create a primitive to fully support concurrent external stores with the `use` API:
+
+```js
+const value = use(store);
+```
+
+Our goal is to allow external state to be read during render without tearing, and to work seamlessly with all of the concurrent features React offers.
+
+This research is still early. We'll share more, and what the new APIs will look like, when we're further along.
+
+---
+
+_Thanks to [Aurora Scharff](https://bsky.app/profile/aurorascharff.no), [Dan Abramov](https://bsky.app/profile/danabra.mov), [Eli White](https://twitter.com/Eli_White), [Lauren Tan](https://bsky.app/profile/no.lol), [Luna Wei](https://github.com/lunaleaps), [Matt Carroll](https://twitter.com/mattcarrollcode), [Jack Pope](https://jackpope.me), [Jason Bonta](https://threads.net/someextent), [Jordan Brown](https://github.com/jbrown215), [Jordan Eldredge](https://bsky.app/profile/capt.dev), [Mofei Zhang](https://threads.net/z_mofei), [Sebastien Lorber](https://bsky.app/profile/sebastienlorber.com), [Sebastian Markbåge](https://bsky.app/profile/sebmarkbage.calyptus.eu), and [Tim Yung](https://github.com/yungsters) for reviewing this post._
diff --git a/src/content/blog/index.md b/src/content/blog/index.md
index 33e1c2bb5..47f76fae8 100644
--- a/src/content/blog/index.md
+++ b/src/content/blog/index.md
@@ -4,7 +4,11 @@ title: React Blog
+<<<<<<< HEAD
React チームからの公式な更新のお知らせはこのブログに掲載されます。リリースノートや非推奨化のお知らせなどの重要なことはすべて、まずこちらに掲載されます。
+=======
+This blog is the official source for the updates from the React team. Anything important, including release notes or deprecation notices, will be posted here first.
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
Bluesky の [@react.dev](https://bsky.app/profile/react.dev) や Twitter の [@reactjs](https://twitter.com/reactjs) アカウントをフォローすることもできますが、このブログさえ読んでいれば、重要なことを見逃す心配はありません。
@@ -16,7 +20,19 @@ Bluesky の [@react.dev](https://bsky.app/profile/react.dev) や Twitter の [@r
-
+
+
+In React Labs posts, we write about projects in active research and development. In this post, we're sharing two new experimental features that are ready to try today, and sharing other areas we're working on now ...
+
+
+
+
+
+We are releasing the compiler's first Release Candidate (RC) today.
+
+
+
+
Today, we’re deprecating Create React App for new apps, and encouraging existing apps to migrate to a framework, or to migrate to a build tool like Vite, Parcel, or RSBuild. We’re also providing docs for when a framework isn’t a good fit for your project, you want to build your own framework, or you just want to learn how React works by building a React app from scratch ...
diff --git a/src/content/community/conferences.md b/src/content/community/conferences.md
index 2422a09ce..88eb8f344 100644
--- a/src/content/community/conferences.md
+++ b/src/content/community/conferences.md
@@ -10,16 +10,6 @@ title: React カンファレンス
## Upcoming Conferences {/*upcoming-conferences*/}
-### React Paris 2025 {/*react-paris-2025*/}
-March 20 - 21, 2025. In-person in Paris, France (hybrid event)
-
-[Website](https://react.paris/) - [Twitter](https://x.com/BeJS_)
-
-### React Native Connection 2025 {/*react-native-connection-2025*/}
-April 3 (Reanimated Training) + April 4 (Conference), 2025. Paris, France.
-
-[Website](https://reactnativeconnection.io/) - [X](https://x.com/reactnativeconn) - [Bluesky](https://bsky.app/profile/reactnativeconnect.bsky.social)
-
### CityJS London 2025 {/*cityjs-london*/}
April 23 - 25, 2025. In-person in London, UK
@@ -35,6 +25,11 @@ May 27 - 31, 2025. In-person in Athens, Greece
[Website](https://athens.cityjsconf.org/) - [Twitter](https://x.com/cityjsconf) - [Bluesky](https://bsky.app/profile/cityjsconf.bsky.social)
+### React Norway 2025 {/*react-norway-2025*/}
+June 13, 2025. In-person in Oslo, Norway + remote (virtual event)
+
+[Website](https://reactnorway.com/) - [Twitter](https://x.com/ReactNorway)
+
### React Summit 2025 {/*react-summit-2025*/}
June 13 - 17, 2025. In-person in Amsterdam, Netherlands + remote (hybrid event)
@@ -50,14 +45,39 @@ September 2-4, 2025. Wrocław, Poland.
[Website](https://www.reactuniverseconf.com/) - [Twitter](https://twitter.com/react_native_eu) - [LinkedIn](https://www.linkedin.com/events/reactuniverseconf7163919537074118657/)
+### React Conf 2025 {/*react-conf-2025*/}
+October 7-8, 2025. Henderson, Nevada, USA and free livestream
+
+[Website](https://conf.react.dev/) - [Twitter](https://x.com/reactjs) - [Bluesky](https://bsky.app/profile/react.dev)
+
### React India 2025 {/*react-india-2025*/}
October 31 - November 01, 2025. In-person in Goa, India (hybrid event) + Oct 15 2025 - remote day
[Website](https://www.reactindia.io) - [Twitter](https://twitter.com/react_india) - [Facebook](https://www.facebook.com/ReactJSIndia) - [Youtube](https://www.youtube.com/channel/UCaFbHCBkPvVv1bWs_jwYt3w)
+### React Summit US 2025 {/*react-summit-us-2025*/}
+November 18 - 21, 2025. In-person in New York, USA + remote (hybrid event)
+
+[Website](https://reactsummit.us/) - [Twitter](https://x.com/reactsummit)
+
+### React Advanced London 2025 {/*react-advanced-london-2025*/}
+November 28 & December 1, 2025. In-person in London, UK + online (hybrid event)
+
+[Website](https://reactadvanced.com/) - [Twitter](https://x.com/reactadvanced)
+
## Past Conferences {/*past-conferences*/}
+### React Paris 2025 {/*react-paris-2025*/}
+March 20 - 21, 2025. In-person in Paris, France (hybrid event)
+
+[Website](https://react.paris/) - [Twitter](https://x.com/BeJS_)
+
+### React Native Connection 2025 {/*react-native-connection-2025*/}
+April 3 (Reanimated Training) + April 4 (Conference), 2025. Paris, France.
+
+[Website](https://reactnativeconnection.io/) - [X](https://x.com/reactnativeconn) - [Bluesky](https://bsky.app/profile/reactnativeconnect.bsky.social)
+
### React Day Berlin 2024 {/*react-day-berlin-2024*/}
December 13 & 16, 2024. In-person in Berlin, Germany + remote (hybrid event)
diff --git a/src/content/community/index.md b/src/content/community/index.md
index 34f01c130..da33f35d8 100644
--- a/src/content/community/index.md
+++ b/src/content/community/index.md
@@ -29,4 +29,8 @@ Stack Overflow は、コードレベルの質問をしたい場合や、特定
## ニュース {/*news*/}
+<<<<<<< HEAD
React の最新ニュースについては、[Twitter の **@reactjs**](https://twitter.com/reactjs) と、このウェブサイト上の[公式 React ブログ](/blog/)をフォローしてください。
+=======
+For the latest news about React, [follow **@reactjs** on Twitter](https://twitter.com/reactjs), [**@react.dev** on Bluesky](https://bsky.app/profile/react.dev) and the [official React blog](/blog/) on this website.
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
diff --git a/src/content/community/meetups.md b/src/content/community/meetups.md
index 43b50b3d7..d8830dd47 100644
--- a/src/content/community/meetups.md
+++ b/src/content/community/meetups.md
@@ -38,7 +38,7 @@ title: React ミーティング
## Canada {/*canada*/}
* [Halifax, NS](https://www.meetup.com/Halifax-ReactJS-Meetup/)
-* [Montreal, QC - React Native](https://www.meetup.com/fr-FR/React-Native-MTL/)
+* [Montreal, QC](https://guild.host/react-montreal/)
* [Vancouver, BC](https://www.meetup.com/ReactJS-Vancouver-Meetup/)
* [Ottawa, ON](https://www.meetup.com/Ottawa-ReactJS-Meetup/)
* [Saskatoon, SK](https://www.meetup.com/saskatoon-react-meetup/)
@@ -47,6 +47,9 @@ title: React ミーティング
## Colombia {/*colombia*/}
* [Medellin](https://www.meetup.com/React-Medellin/)
+## Czechia {/*czechia*/}
+* [Prague](https://guild.host/react-prague/)
+
## Denmark {/*denmark*/}
* [Aalborg](https://www.meetup.com/Aalborg-React-React-Native-Meetup/)
* [Aarhus](https://www.meetup.com/Aarhus-ReactJS-Meetup/)
@@ -78,7 +81,7 @@ title: React ミーティング
* [Thessaloniki](https://www.meetup.com/Thessaloniki-ReactJS-Meetup/)
## India {/*india*/}
-* [Ahmedabad](https://www.meetup.com/react-ahmedabad/)
+* [Ahmedabad](https://reactahmedabad.dev/)
* [Bangalore (React)](https://www.meetup.com/ReactJS-Bangalore/)
* [Bangalore (React Native)](https://www.meetup.com/React-Native-Bangalore-Meetup)
* [Chennai](https://www.linkedin.com/company/chennaireact)
@@ -166,6 +169,7 @@ title: React ミーティング
* [Cleveland, OH - ReactJS](https://www.meetup.com/Cleveland-React/)
* [Columbus, OH - ReactJS](https://www.meetup.com/ReactJS-Columbus-meetup/)
* [Dallas, TX - ReactJS](https://www.meetup.com/ReactDallas/)
+* [Denver, CO - React Denver](https://reactdenver.com/)
* [Detroit, MI - Detroit React User Group](https://www.meetup.com/Detroit-React-User-Group/)
* [Indianapolis, IN - React.Indy](https://www.meetup.com/React-Indy)
* [Irvine, CA - ReactJS](https://www.meetup.com/ReactJS-OC/)
diff --git a/src/content/learn/build-a-react-app-from-scratch.md b/src/content/learn/build-a-react-app-from-scratch.md
index b00205388..5f635a55c 100644
--- a/src/content/learn/build-a-react-app-from-scratch.md
+++ b/src/content/learn/build-a-react-app-from-scratch.md
@@ -65,7 +65,11 @@ Rsbuild には、ファストリフレッシュ、JSX、TypeScript、スタイ
#### React Native 用の Metro {/*react-native*/}
+<<<<<<< HEAD
React Native をゼロから始める場合は、React Native 用の JavaScript バンドラである [Metro](https://metrobundler.dev/) を使用する必要があります。Metro は iOS や Android などのプラットフォーム向けのバンドル機能をサポートしていますが、上記で紹介したツールと比較すると多くの機能が不足しています。プロジェクトが React Native のサポートを必要としているのでない限り、Vite、Parcel、または Rsbuild から始めることをお勧めします。
+=======
+If you're starting from scratch with React Native you'll need to use [Metro](https://metrobundler.dev/), the JavaScript bundler for React Native. Metro supports bundling for platforms like iOS and Android, but lacks many features when compared to the tools here. We recommend starting with Vite, Parcel, or Rsbuild unless your project requires React Native support.
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
@@ -83,7 +87,7 @@ React エコシステムには、これらの問題に対するツールがた
以下のライブラリの使用をお勧めします。
-- [React Router](https://reactrouter.com/start/framework/custom)
+- [React Router](https://reactrouter.com/start/data/custom)
- [Tanstack Router](https://tanstack.com/router/latest)
@@ -115,10 +119,17 @@ GraphQL API からデータを取得する場合、以下の使用をお勧め
ルートごとにコードを分割するだけでなく、バンドルやデータフェッチと統合することで、アプリの初期読み込み時間とアプリの最大可視コンテンツのレンダー時間 ([Largest Contentful Paint](https://web.dev/articles/lcp)) を短縮できます。
+<<<<<<< HEAD
コード分割の手順については、ビルドツールのドキュメントを参照してください。
- [Vite のビルド最適化](https://v3.vitejs.dev/guide/features.html#build-optimizations)
- [Parcel のコード分割](https://parceljs.org/features/code-splitting/)
- [Rsbuild のコード分割](https://rsbuild.dev/guide/optimization/code-splitting)
+=======
+For code-splitting instructions, see your build tool docs:
+- [Vite build optimizations](https://vite.dev/guide/features.html#build-optimizations)
+- [Parcel code splitting](https://parceljs.org/features/code-splitting/)
+- [Rsbuild code splitting](https://rsbuild.dev/guide/optimization/code-splitting)
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
### アプリケーションパフォーマンスの向上 {/*improving-application-performance*/}
diff --git a/src/content/learn/creating-a-react-app.md b/src/content/learn/creating-a-react-app.md
index 509deca01..50b04dfe7 100644
--- a/src/content/learn/creating-a-react-app.md
+++ b/src/content/learn/creating-a-react-app.md
@@ -32,7 +32,11 @@ React を使って新しいアプリやウェブサイトを作成したい場
npx create-next-app@latest
+<<<<<<< HEAD
Next.js は [Vercel](https://vercel.com/) によってメンテナンスされています。Next.js アプリを Node.js やサーバレスホスティング、または独自のサーバに[デプロイできます](https://nextjs.org/docs/app/building-your-application/deploying)。Next.js はまた、サーバを必要としない[静的エクスポート](https://nextjs.org/docs/app/building-your-application/deploying/static-exports)をサポートしています。Vercel はさらにオプトインの有料クラウドサービスも提供しています。
+=======
+Next.js is maintained by [Vercel](https://vercel.com/). You can [deploy a Next.js app](https://nextjs.org/docs/app/building-your-application/deploying) to any hosting provider that supports Node.js or Docker containers, or to your own server. Next.js also supports [static export](https://nextjs.org/docs/app/building-your-application/deploying/static-exports) which doesn't require a server.
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
### React Router (v7) {/*react-router-v7*/}
@@ -106,7 +110,11 @@ Next.js の App Router は、[サスペンス (Suspense) を使用したデー
ゼロから始めることでより柔軟性が得られますが、ルーティング、データフェッチ、その他の一般的な使用パターンにどのツールを使用するかを選択する必要があります。これは、既存のフレームワークを使用する代わりに自分自身でフレームワークを構築するようなものです。[おすすめのフルスタックフレームワーク](#full-stack-frameworks)には、これらの問題に対する組み込みの解決策があります。
+<<<<<<< HEAD
独自のソリューションを構築したい場合は、[ゼロからの React アプリ構築](/learn/build-a-react-app-from-scratch)ガイドを参照し、[Vite](https://vite.dev/)、[Parcel](https://parceljs.org/)、または [RSbuild](https://rsbuild.dev/) のようなビルドツールを使って新しい React プロジェクトをセットアップする方法を確認してください。
+=======
+If you want to build your own solutions, see our guide to [build a React app from Scratch](/learn/build-a-react-app-from-scratch) for instructions on how to set up a new React project starting with a build tool like [Vite](https://vite.dev/), [Parcel](https://parceljs.org/), or [RSbuild](https://rsbuild.dev/).
+>>>>>>> 65d297e93b36be5370e58ab7828d022c741ecbe2
-----
diff --git a/src/content/learn/preserving-and-resetting-state.md b/src/content/learn/preserving-and-resetting-state.md
index 008f9c3a5..b94d38918 100644
--- a/src/content/learn/preserving-and-resetting-state.md
+++ b/src/content/learn/preserving-and-resetting-state.md
@@ -2011,7 +2011,7 @@ export default function ContactList() {
+ 
+ 
+ 
+