Releases: facebook/react
19.0.0 (December 5, 2024)
Below is a list of all new features, APIs, deprecations, and breaking changes. Read React 19 release post and React 19 upgrade guide for more information.
Note: To help make the upgrade to React 19 easier, weβve published a react@18.3 release that is identical to 18.2 but adds warnings for deprecated APIs and other changes that are needed for React 19. We recommend upgrading to React 18.3.1 first to help identify any issues before upgrading to React 19.
New Features
React
- Actions:
startTransitioncan now accept async functions. Functions passed tostartTransitionare called βActionsβ. A given Transition can include one or more Actions which update state in the background and update the UI with one commit. In addition to updating state, Actions can now perform side effects including async requests, and the Action will wait for the work to finish before finishing the Transition. This feature allows Transitions to include side effects likefetch()in the pending state, and provides support for error handling, and optimistic updates. useActionState: is a new hook to order Actions inside of a Transition with access to the state of the action, and the pending state. It accepts a reducer that can call Actions, and the initial state used for first render. It also accepts an optional string that is used if the action is passed to a formactionprop to support progressive enhancement in forms.useOptimistic: is a new hook to update state while a Transition is in progress. It returns the state, and a set function that can be called inside a transition to βoptimisticallyβ update the state to expected final value immediately while the Transition completes in the background. When the transition finishes, the state is updated to the new value.use: is a new API that allows reading resources in render. In React 19,useaccepts a promise or Context. If provided a promise,usewill suspend until a value is resolved.usecan only be used in render but can be called conditionally.refas a prop: Refs can now be used as props, removing the need forforwardRef.- Suspense sibling pre-warming: When a component suspends, React will immediately commit the fallback of the nearest Suspense boundary, without waiting for the entire sibling tree to render. After the fallback commits, React will schedule another render for the suspended siblings to βpre-warmβ lazy requests.
React DOM Client
<form> actionprop: Form Actions allow you to manage forms automatically and integrate withuseFormStatus. When a<form> actionsucceeds, React will automatically reset the form for uncontrolled components. The form can be reset manually with the newrequestFormResetAPI.<button> and <input> formActionprop: Actions can be passed to theformActionprop to configure form submission behavior. This allows using different Actions depending on the input.useFormStatus: is a new hook that provides the status of the parent<form> action, as if the form was a Context provider. The hook returns the values:pending,data,method, andaction.- Support for Document Metadata: Weβve added support for rendering document metadata tags in components natively. React will automatically hoist them into the
<head>section of the document. - Support for Stylesheets: React 19 will ensure stylesheets are inserted into the
<head>on the client before revealing the content of a Suspense boundary that depends on that stylesheet. - Support for async scripts: Async scripts can be rendered anywhere in the component tree and React will handle ordering and deduplication.
- Support for preloading resources: React 19 ships with
preinit,preload,prefetchDNS, andpreconnectAPIs to optimize initial page loads by moving discovery of additional resources like fonts out of stylesheet loading. They can also be used to prefetch resources used by an anticipated navigation.
React DOM Server
- Added
prerenderandprerenderToNodeStreamAPIs for static site generation. They are designed to work with streaming environments like Node.js Streams and Web Streams. UnlikerenderToString, they wait for data to load for HTML generation.
React Server Components
- RSC features such as directives, server components, and server functions are now stable. This means libraries that ship with Server Components can now target React 19 as a peer dependency with a react-server export condition for use in frameworks that support the Full-stack React Architecture. The underlying APIs used to implement a React Server Components bundler or framework do not follow semver and may break between minors in React 19.x. See docs for how to support React Server Components.
Deprecations
- Deprecated:
element.refaccess: React 19 supports ref as a prop, so weβre deprecatingelement.refin favor ofelement.props.ref. Accessing will result in a warning. react-test-renderer: In React 19, react-test-renderer logs a deprecation warning and has switched to concurrent rendering for web usage. We recommend migrating your tests to @testinglibrary.com/docs/react-testing-library/intro/) or @testingesting-library.com/docs/react-native-testing-library/intro)
Breaking Changes
React 19 brings in a number of breaking changes, including the removals of long-deprecated APIs. We recommend first upgrading to 18.3.1, where we've added additional deprecation warnings. Check out the upgrade guide for more details and guidance on codemodding.
React
- New JSX Transform is now required: We introduced a new JSX transform in 2020 to improve bundle size and use JSX without importing React. In React 19, weβre adding additional improvements like using ref as a prop and JSX speed improvements that require the new transform.
- Errors in render are not re-thrown: Errors that are not caught by an Error Boundary are now reported to window.reportError. Errors that are caught by an Error Boundary are reported to console.error. Weβve introduced
onUncaughtErrorandonCaughtErrormethods tocreateRootandhydrateRootto customize this error handling. - Removed:
propTypes: UsingpropTypeswill now be silently ignored. If required, we recommend migrating to TypeScript or another type-checking solution. - Removed:
defaultPropsfor functions: ES6 default parameters can be used in place. Class components continue to supportdefaultPropssince there is no ES6 alternative. - Removed:
contextTypesandgetChildContext: Legacy Context for class components has been removed in favor of thecontextTypeAPI. - Removed: string refs: Any usage of string refs need to be migrated to ref callbacks.
- Removed: Module pattern factories: A rarely used pattern that can be migrated to regular functions.
- Removed:
React.createFactory: Now that JSX is broadly supported, allcreateFactoryusage can be migrated to JSX components. - Removed:
react-test-renderer/shallow: This has been a re-export of react-shallow-renderer since React 18. If needed, you can continue to use the third-party package directly. We recommend using @testinglibrary.com/docs/react-testing-library/intro/) or @testingesting-library.com/docs/react-native-testing-library/intro) instead.
React DOM
- Removed:
react-dom/test-utils: Weβve movedactfromreact-dom/test-utilsto react. All other utilities have been removed. - Removed:
ReactDOM.render,ReactDOM.hydrate: These have been removed in favor of the concurrent equivalents:ReactDOM.createRootandReactDOM.hydrateRoot. - Removed:
unmountComponentAtNode: Removed in favor ofroot.unmount(). - Removed:
ReactDOM.findDOMNode: You can replaceReactDOM.findDOMNodewith DOM Refs.
Notable Changes
React
<Context>as a provider: You can now render<Context>as a provider instead of<Context.Provider>.- Cleanup functions for refs: When the component unmounts, React will call the cleanup function returned from the ref callback.
useDeferredValueinitial value argument: When provided,useDeferredValuewill return the initial value for the initial render of a component, then schedule a re-render in the background with thedeferredValuereturned.- Support for Custom Elements: React 19 now passes all tests on Custom Elements Everywhere.
- StrictMode changes:
useMemoanduseCallbackwill now reuse the memoized results from the first render, during the second render. Additionally, StrictMode will now double-invoke ref callback functions on initial mount. - UMD builds removed: To load React 19 with a script tag, we recommend using an ESM-based CDN such as esm.sh.
React DOM
- Diffs for hydration errors: In the case of a mismatch, React 19 logs a single error with a diff of the mismatched content.
- Compatibility with third-party scripts and extensions: React will now force a client re-render to fix up any mismatched content caused by elements inserted by third-party JS.
TypeScript Changes
The most common changes can be codemodded with npx types-react-codemod@latest preset-19 ./path-to-your-react-ts-files.
- Removed deprecated TypeScript types:
ReactChild(replacement:React.ReactElement | number | string)ReactFragment(replacement:Iterable<React.ReactNode>)ReactNodeArray(replacement:ReadonlyArray<React.ReactNode>)ReactText(replacement:...
eslint-plugin-react-hooks@5.0.0 (Oct 11, 2024)
This release only contains eslint-plugin-react-hooks. Notably, new violations and support for ESLint v9 were added.
eslint-plugin-react-hooks
- New Violations: Component names now need to start with an uppercase letter instead of a non-lowercase letter. This means
_Buttonor_componentare no longer valid. (@kassens) in #25162
For example, infunction _Component() { useState() ^^^^^^^^ A React Hook "useState" is called in function "_Component" which is neither a Component nor a custom React Hook function. }
_Componentshould be renamed toComponent.
- Add support for ESLint v9. (@eps1lon in #28773)
- Consider dispatch from
useActionStatestable. (@eps1lon in #29665) - Accept
asexpression in callback. (@StyleShit in #28202) - Accept
asexpressions in deps array. (@StyleShit in #28189) - Treat
React.use()the same asuse(). (@kassens in #27769) - Move
use()lint to non-experimental. (@kassens in #27768) - Support Flow
asexpressions. (@cpojer in #27590) - Allow
useEffect(fn, undefined). (@kassens in #27525) - Disallow hooks in async functions. (@acdlite in #27045)
- Rename experimental
useEventtouseEffectEvent. (@sebmarkbage in #25881) - Lint for presence of
useEventfunctions in dependency lists. (@poteto in #25512) - Check
useEventreferences instead. (@poteto in #25319) - Update
RulesOfHookswithuseEventrules. (@poteto in #25285)
18.3.1 (April 26, 2024)
- Export
actfromreactf1338f
18.3.0 (April 25, 2024)
This release is identical to 18.2 but adds warnings for deprecated APIs and other changes that are needed for React 19.
Read the React 19 Upgrade Guide for more info.
React
- Allow writing to
this.refsto support string ref codemod 909071 - Warn for deprecated
findDOMNodeoutside StrictMode c3b283 - Warn for deprecated
test-utilsmethods d4ea75 - Warn for deprecated Legacy Context outside StrictMode 415ee0
- Warn for deprecated string refs outside StrictMode #25383
- Warn for deprecated
defaultPropsfor function components #25699 - Warn when spreading
key#25697 - Warn when using
actfromtest-utilsd4ea75
React DOM
18.2.0 (June 14, 2022)
React DOM
- Provide a component stack as a second argument to
onRecoverableError. (@gnoff in #24591) - Fix hydrating into
documentcausing a blank page on mismatch. (@gnoff in #24523) - Fix false positive hydration errors with Suspense. (@gnoff in #24480 and @acdlite in #24532)
- Fix ignored
setStatein Safari when adding an iframe. (@gaearon in #24459)
React DOM Server
- Pass information about server errors to the client. (@salazarm and @gnoff in #24551 and #24591)
- Allow to provide a reason when aborting the HTML stream. (@gnoff in #24680)
- Eliminate extraneous text separators in the HTML where possible. (@gnoff in #24630)
- Disallow complex children inside
<title>elements to match the browser constraints. (@gnoff in #24679) - Fix buffering in some worker environments by explicitly setting
highWaterMarkto0. (@jplhomer in #24641)
Server Components (Experimental)
18.1.0 (April 26, 2022)
React DOM
- Fix the false positive warning about
react-dom/clientwhen using UMD bundle. (@alireza-molaee in #24274) - Fix
suppressHydrationWarningto work in production too. (@gaearon in #24271) - Fix
componentWillUnmountfiring twice inside of Suspense. (@acdlite in #24308) - Fix some transition updates being ignored. (@acdlite in #24353)
- Fix
useDeferredValuecausing an infinite loop when passed an unmemoized value. (@acdlite in #24247) - Fix throttling of revealing Suspense fallbacks. (@sunderls in #24253)
- Fix an inconsistency in whether the props object is the same between renders. (@Andarist and @acdlite in #24421)
- Fix a missing warning about a
setStateloop inuseEffect. (@gaearon in #24298) - Fix a spurious hydration error. (@gnoff in #24404)
- Warn when calling
setStateinuseInsertionEffect. (@gaearon in #24295) - Ensure the reason for hydration errors is always displayed. (@gaearon in #24276)
React DOM Server
- Fix escaping for the
bootstrapScriptContentcontents. (@gnoff in #24385) - Significantly improve performance of
renderToPipeableStream. (@gnoff in #24291)
ESLint Plugin: React Hooks
- Fix false positive errors with a large number of branches. (@scyron6 in #24287)
- Don't consider a known dependency stable when the variable is reassigned. (@afzalsayed96 in #24343)
Use Subscription
18.0.0 (March 29, 2022)
Below is a list of all new features, APIs, deprecations, and breaking changes.
Read React 18 release post and React 18 upgrade guide for more information.
New Features
React
useIdis a new hook for generating unique IDs on both the client and server, while avoiding hydration mismatches. It is primarily useful for component libraries integrating with accessibility APIs that require unique IDs. This solves an issue that already exists in React 17 and below, but itβs even more important in React 18 because of how the new streaming server renderer delivers HTML out-of-order.startTransitionanduseTransitionlet you mark some state updates as not urgent. Other state updates are considered urgent by default. React will allow urgent state updates (for example, updating a text input) to interrupt non-urgent state updates (for example, rendering a list of search results).useDeferredValuelets you defer re-rendering a non-urgent part of the tree. It is similar to debouncing, but has a few advantages compared to it. There is no fixed time delay, so React will attempt the deferred render right after the first render is reflected on the screen. The deferred render is interruptible and doesn't block user input.useSyncExternalStoreis a new hook that allows external stores to support concurrent reads by forcing updates to the store to be synchronous. It removes the need foruseEffectwhen implementing subscriptions to external data sources, and is recommended for any library that integrates with state external to React.useInsertionEffectis a new hook that allows CSS-in-JS libraries to address performance issues of injecting styles in render. Unless youβve already built a CSS-in-JS library we donβt expect you to ever use this. This hook will run after the DOM is mutated, but before layout effects read the new layout. This solves an issue that already exists in React 17 and below, but is even more important in React 18 because React yields to the browser during concurrent rendering, giving it a chance to recalculate layout.
React DOM Client
These new APIs are now exported from react-dom/client:
createRoot: New method to create a root torenderorunmount. Use it instead ofReactDOM.render. New features in React 18 don't work without it.hydrateRoot: New method to hydrate a server rendered application. Use it instead ofReactDOM.hydratein conjunction with the new React DOM Server APIs. New features in React 18 don't work without it.
Both createRoot and hydrateRoot accept a new option called onRecoverableError in case you want to be notified when React recovers from errors during rendering or hydration for logging. By default, React will use reportError, or console.error in the older browsers.
React DOM Server
These new APIs are now exported from react-dom/server and have full support for streaming Suspense on the server:
renderToPipeableStream: for streaming in Node environments.renderToReadableStream: for modern edge runtime environments, such as Deno and Cloudflare workers.
The existing renderToString method keeps working but is discouraged.
Deprecations
react-dom:ReactDOM.renderhas been deprecated. Using it will warn and run your app in React 17 mode.react-dom:ReactDOM.hydratehas been deprecated. Using it will warn and run your app in React 17 mode.react-dom:ReactDOM.unmountComponentAtNodehas been deprecated.react-dom:ReactDOM.renderSubtreeIntoContainerhas been deprecated.react-dom/server:ReactDOMServer.renderToNodeStreamhas been deprecated.
Breaking Changes
React
- Automatic batching: This release introduces a performance improvement that changes to the way React batches updates to do more batching automatically. See Automatic batching for fewer renders in React 18 for more info. In the rare case that you need to opt out, wrap the state update in
flushSync. - Stricter Strict Mode: In the future, React will provide a feature that lets components preserve state between unmounts. To prepare for it, React 18 introduces a new development-only check to Strict Mode. React will automatically unmount and remount every component, whenever a component mounts for the first time, restoring the previous state on the second mount. If this breaks your app, consider removing Strict Mode until you can fix the components to be resilient to remounting with existing state.
- Consistent useEffect timing: React now always synchronously flushes effect functions if the update was triggered during a discrete user input event such as a click or a keydown event. Previously, the behavior wasn't always predictable or consistent.
- Stricter hydration errors: Hydration mismatches due to missing or extra text content are now treated like errors instead of warnings. React will no longer attempt to "patch up" individual nodes by inserting or deleting a node on the client in an attempt to match the server markup, and will revert to client rendering up to the closest
<Suspense>boundary in the tree. This ensures the hydrated tree is consistent and avoids potential privacy and security holes that can be caused by hydration mismatches. - Suspense trees are always consistent: If a component suspends before it's fully added to the tree, React will not add it to the tree in an incomplete state or fire its effects. Instead, React will throw away the new tree completely, wait for the asynchronous operation to finish, and then retry rendering again from scratch. React will render the retry attempt concurrently, and without blocking the browser.
- Layout Effects with Suspense: When a tree re-suspends and reverts to a fallback, React will now clean up layout effects, and then re-create them when the content inside the boundary is shown again. This fixes an issue which prevented component libraries from correctly measuring layout when used with Suspense.
- New JS Environment Requirements: React now depends on modern browsers features including
Promise,Symbol, andObject.assign. If you support older browsers and devices such as Internet Explorer which do not provide modern browser features natively or have non-compliant implementations, consider including a global polyfill in your bundled application.
Scheduler (Experimental)
- Remove unstable
scheduler/tracingAPI
Notable Changes
React
- Components can now render
undefined: React no longer throws if you returnundefinedfrom a component. This makes the allowed component return values consistent with values that are allowed in the middle of a component tree. We suggest to use a linter to prevent mistakes like forgetting areturnstatement before JSX. - In tests,
actwarnings are now opt-in: If you're running end-to-end tests, theactwarnings are unnecessary. We've introduced an opt-in mechanism so you can enable them only for unit tests where they are useful and beneficial. - No warning about
setStateon unmounted components: Previously, React warned about memory leaks when you callsetStateon an unmounted component. This warning was added for subscriptions, but people primarily run into it in scenarios where setting state is fine, and workarounds make the code worse. We've removed this warning. - No suppression of console logs: When you use Strict Mode, React renders each component twice to help you find unexpected side effects. In React 17, we've suppressed console logs for one of the two renders to make the logs easier to read. In response to community feedback about this being confusing, we've removed the suppression. Instead, if you have React DevTools installed, the second log's renders will be displayed in grey, and there will be an option (off by default) to suppress them completely.
- Improved memory usage: React now cleans up more internal fields on unmount, making the impact from unfixed memory leaks that may exist in your application code less severe.
React DOM Server
renderToString: Will no longer error when suspending on the server. Instead, it will emit the fallback HTML for the closest<Suspense>boundary and then retry rendering the same content on the client. It is still recommended that you switch to a streaming API likerenderToPipeableStreamorrenderToReadableStreaminstead.renderToStaticMarkup: Will no longer error when suspending on the server. Instead, it will emit the fallback HTML for the closest<Suspense>boundary and retry rendering on the client.
All Changes
React
17.0.2 (March 22, 2021)
React DOM
- Remove an unused dependency to address the
SharedArrayBuffercross-origin isolation warning. (@koba04 and @bvaughn in #20831, #20832, and #20840)
Artifacts
- react: https://unpkg.com/react@17.0.2/umd/
- react-art: https://unpkg.com/react-art@17.0.2/umd/
- react-dom: https://unpkg.com/react-dom@17.0.2/umd/
- react-is: https://unpkg.com/react-is@17.0.2/umd/
- react-test-renderer: https://unpkg.com/react-test-renderer@17.0.2/umd/
- scheduler: https://unpkg.com/scheduler@0.20.2/umd/
17.0.1 (October 22, 2020)
17.0.0 (October 20, 2020)
Today, we are releasing React 17!
Learn more about React 17 and how to update to it on the official React blog.
React
- Add
react/jsx-runtimeandreact/jsx-dev-runtimefor the new JSX transform. (@lunaruan in #18299) - Build component stacks from native error frames. (@sebmarkbage in #18561)
- Allow to specify
displayNameon context for improved stacks. (@eps1lon in #18224) - Prevent
'use strict'from leaking in the UMD bundles. (@koba04 in #19614) - Stop using
fb.mefor redirects. (@cylim in #19598)
React DOM
- Delegate events to roots instead of
document. (@trueadm in #18195 and others) - Clean up all effects before running any next effects. (@bvaughn in #17947)
- Run
useEffectcleanup functions asynchronously. (@bvaughn in #17925) - Use browser
focusinandfocusoutforonFocusandonBlur. (@trueadm in #19186) - Make all
Captureevents use the browser capture phase. (@trueadm in #19221) - Don't emulate bubbling of the
onScrollevent. (@gaearon in #19464) - Throw if
forwardReformemocomponent returnsundefined. (@gaearon in #19550) - Remove event pooling. (@trueadm in #18969)
- Stop exposing internals that wonβt be needed by React Native Web. (@necolas in #18483)
- Attach all known event listeners when the root mounts. (@gaearon in #19659)
- Disable
consolein the second render pass of DEV mode double render. (@sebmarkbage in #18547) - Deprecate the undocumented and misleading
ReactTestUtils.SimulateNativeAPI. (@gaearon in #13407) - Rename private field names used in the internals. (@gaearon in #18377)
- Don't call User Timing API in development. (@gaearon in #18417)
- Disable console during the repeated render in Strict Mode. (@sebmarkbage in #18547)
- In Strict Mode, double-render components without Hooks too. (@eps1lon in #18430)
- Allow calling
ReactDOM.flushSyncduring lifecycle methods (but warn). (@sebmarkbage in #18759) - Add the
codeproperty to the keyboard event objects. (@bl00mber in #18287) - Add the
disableRemotePlaybackproperty forvideoelements. (@tombrowndev in #18619) - Add the
enterKeyHintproperty forinputelements. (@eps1lon in #18634) - Warn when no
valueis provided to<Context.Provider>. (@charlie1404 in #19054) - Warn when
memoorforwardRefcomponents returnundefined. (@bvaughn in #19550) - Improve the error message for invalid updates. (@JoviDeCroock in #18316)
- Exclude forwardRef and memo from stack frames. (@sebmarkbage in #18559)
- Improve the error message when switching between controlled and uncontrolled inputs. (@vcarl in #17070)
- Keep
onTouchStart,onTouchMove, andonWheelpassive. (@gaearon in #19654) - Fix
setStatehanging in development inside a closed iframe. (@gaearon in #19220) - Fix rendering bailout for lazy components with
defaultProps. (@jddxf in #18539) - Fix a false positive warning when
dangerouslySetInnerHTMLisundefined. (@eps1lon in #18676) - Fix Test Utils with non-standard
requireimplementation. (@just-boris in #18632) - Fix
onBeforeInputreporting an incorrectevent.type. (@eps1lon in #19561) - Fix
event.relatedTargetreported asundefinedin Firefox. (@claytercek in #19607) - Fix "unspecified error" in IE11. (@hemakshis in #19664)
- Fix rendering into a shadow root. (@Jack-Works in #15894)
- Fix
movementX/Ypolyfill with capture events. (@gaearon in #19672) - Use delegation for
onSubmitandonResetevents. (@gaearon in #19333) - Improve memory usage. (@trueadm in #18970)
React DOM Server
- Make
useCallbackbehavior consistent withuseMemofor the server renderer. (@alexmckenley in #18783) - Fix state leaking when a function component throws. (@pmaccart in #19212)
React Test Renderer
- Improve
findByTypeerror message. (@henryqdineen in #17439)
Concurrent Mode (Experimental)
- Revamp the priority batching heuristics. (@acdlite in #18796)
- Add the
unstable_prefix before the experimental APIs. (@acdlite in #18825) - Remove
unstable_discreteUpdatesandunstable_flushDiscreteUpdates. (@trueadm in #18825) - Remove the
timeoutMsargument. (@acdlite in #19703) - Disable
<div hidden />prerendering in favor of a different future API. (@acdlite in #18917) - Add
unstable_expectedLoadTimeto Suspense for CPU-bound trees. (@acdlite in #19936) - Add an experimental
unstable_useOpaqueIdentifierHook. (@lunaruan in #17322) - Add an experimental
unstable_startTransitionAPI. (@rickhanlonii in #19696) - Using
actin the test renderer no longer flushes Suspense fallbacks. (@acdlite in #18596) - Use global render timeout for CPU Suspense. (@sebmarkbage in #19643)
- Clear the existing root content before mounting. (@bvaughn in #18730)
- Fix a bug with error boundaries. (@acdlite in #18265)
- Fix a bug causing dropped updates in a suspended tree. (@acdlite in #18384 and #18457)
- Fix a bug causing dropped render phase updates. (@acdlite in #18537)
- Fix a bug in Suspens...