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Note: To help make the upgrade to React 19 easier, we’ve 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: startTransition can now accept async functions. Functions passed to startTransition are called “Actions”. 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 like fetch() 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 form action prop 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 “optimistically” 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, use accepts a promise or Context. If provided a promise, use will suspend until a value is resolved. use can only be used in render but can be called conditionally.
ref as a prop: Refs can now be used as props, removing the need for forwardRef.
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 “pre-warm” lazy requests.
React DOM Client
<form> action prop: Form Actions allow you to manage forms automatically and integrate with useFormStatus. When a <form> action succeeds, React will automatically reset the form for uncontrolled components. The form can be reset manually with the new requestFormReset API.
<button> and <input> formAction prop: Actions can be passed to the formAction prop 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, and action.
Support for Document Metadata: We’ve 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, and preconnect APIs 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 prerender and prerenderToNodeStream APIs for static site generation. They are designed to work with streaming environments like Node.js Streams and Web Streams. Unlike renderToString, 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.ref access: React 19 supports ref as a prop, so we’re deprecating element.ref in favor of element.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 @testing-library/react or @testing-library/react-native
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, we’re 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. We’ve introduced onUncaughtError and onCaughtError methods to createRoot and hydrateRoot to customize this error handling.
Removed: propTypes: Using propTypes will now be silently ignored. If required, we recommend migrating to TypeScript or another type-checking solution.
Removed: defaultProps for functions: ES6 default parameters can be used in place. Class components continue to support defaultProps since there is no ES6 alternative.
Removed: contextTypes and getChildContext: Legacy Context for class components has been removed in favor of the contextType API.
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, all createFactory usage can be migrated to JSX components.
Removed: react-dom/test-utils: We’ve moved act from react-dom/test-utils to react. All other utilities have been removed.
Removed: ReactDOM.render, ReactDOM.hydrate: These have been removed in favor of the concurrent equivalents: ReactDOM.createRoot and ReactDOM.hydrateRoot.
Removed: unmountComponentAtNode: Removed in favor of root.unmount().
Removed: ReactDOM.findDOMNode: You can replace ReactDOM.findDOMNode with 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.
useDeferredValue initial value argument: When provided, useDeferredValue will return the initial value for the initial render of a component, then schedule a re-render in the background with the deferredValue returned.
StrictMode changes: useMemo and useCallback will 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)
Moved to prop-types: Requireable, ValidationMap, Validator, WeakValidationMap
Moved to create-react-class: ClassicComponentClass, ClassicComponent, ClassicElement, ComponentSpec, Mixin, ReactChildren, ReactHTML, ReactSVG, SFCFactory
Disallow implicit return in refs: refs can now accept cleanup functions. When you return something else, we can’t tell if you intentionally returned something not meant to clean up or returned the wrong value. Implicit returns of anything but functions will now error.
Require initial argument to useRef: The initial argument is now required to match useState, createContext etc
Refs are mutable by default: Ref objects returned from useRef() are now always mutable instead of sometimes being immutable. This feature was too confusing for users and conflicted with legit cases where refs were managed by React and manually written to.
Strict ReactElement typing: The props of React elements now default to unknown instead of any if the element is typed as ReactElement
JSX namespace in TypeScript: The global JSX namespace is removed to improve interoperability with other libraries using JSX. Instead, the JSX namespace is available from the React package: import { JSX } from 'react'
Better useReducer typings: Most useReducer usage should not require explicit type arguments.
For example,
Fix onChange error message for controlled <select> (#27740 by @Biki-das)
Fix focus restore in child windows after element reorder (#30951 by @ling1726)
Remove render, hydrate, findDOMNode, unmountComponentAtNode, unstable_createEventHandle, unstable_renderSubtreeIntoContainer, and unstable_runWithPriority. Move createRoot and hydrateRoot to react-dom/client. (#28271 by @gnoff)
efps — editor "frames per second". The number of updates assumed to be possible within a second.
Derived from input latency. efps = 1000 / input_latency
Detailed information
🏠 Reference result
The performance result of sanity@latest
Benchmark
latency
p75
p90
p99
blocking time
test duration
article (title)
38ms
44ms
68ms
439ms
817ms
10.9s
article (body)
19ms
21ms
24ms
49ms
90ms
5.4s
article (string inside object)
36ms
38ms
40ms
49ms
0ms
6.2s
article (string inside array)
39ms
41ms
48ms
97ms
136ms
6.6s
recipe (name)
19ms
20ms
22ms
45ms
0ms
7.1s
recipe (description)
18ms
19ms
20ms
28ms
0ms
4.3s
recipe (instructions)
6ms
7ms
9ms
9ms
0ms
3.4s
synthetic (title)
51ms
53ms
56ms
94ms
681ms
12.9s
synthetic (string inside object)
52ms
54ms
63ms
156ms
414ms
7.7s
🧪 Experiment result
The performance result of this branch
Benchmark
latency
p75
p90
p99
blocking time
test duration
article (title)
41ms
62ms
72ms
537ms
746ms
11.3s
article (body)
20ms
23ms
27ms
177ms
228ms
5.9s
article (string inside object)
37ms
38ms
42ms
186ms
169ms
6.9s
article (string inside array)
42ms
45ms
53ms
223ms
377ms
7.2s
recipe (name)
19ms
20ms
22ms
49ms
0ms
6.4s
recipe (description)
18ms
19ms
19ms
38ms
0ms
4.3s
recipe (instructions)
6ms
7ms
9ms
9ms
0ms
3.1s
synthetic (title)
53ms
56ms
60ms
115ms
380ms
12.3s
synthetic (string inside object)
48ms
51ms
59ms
518ms
972ms
8.4s
📚 Glossary
column definitions
benchmark — the name of the test, e.g. "article", followed by the label of the field being measured, e.g. "(title)".
latency — the time between when a key was pressed and when it was rendered. derived from a set of samples. the median (p50) is shown to show the most common latency.
p75 — the 75th percentile of the input latency in the test run. 75% of the sampled inputs in this benchmark were processed faster than this value. this provides insight into the upper range of typical performance.
p90 — the 90th percentile of the input latency in the test run. 90% of the sampled inputs were faster than this. this metric helps identify slower interactions that occurred less frequently during the benchmark.
p99 — the 99th percentile of the input latency in the test run. only 1% of sampled inputs were slower than this. this represents the worst-case scenarios encountered during the benchmark, useful for identifying potential performance outliers.
blocking time — the total time during which the main thread was blocked, preventing user input and UI updates. this metric helps identify performance bottlenecks that may cause the interface to feel unresponsive.
test duration — how long the test run took to complete.
Because you closed this PR without merging, Renovate will ignore this update. You will not get PRs for any future 19.x releases. But if you manually upgrade to 19.x then Renovate will re-enable minor and patch updates automatically.
If you accidentally closed this PR, or if you changed your mind: rename this PR to get a fresh replacement PR.
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This PR contains the following updates:
^18.3.1
->^19.0.0
^18.2.0
->^19.0.0
^18.3.1
->^19.0.0
^18.2.0
->^19.0.0
^18.2.0
->^19.0.0
Release Notes
facebook/react (react)
v19.0.0
Compare Source
facebook/react (react-dom)
v19.0.0
Compare Source
facebook/react (react-is)
v19.0.0
Compare Source
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.
New Features
React
startTransition
can now accept async functions. Functions passed tostartTransition
are called “Actions”. 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 formaction
prop 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 “optimistically” 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,use
accepts a promise or Context. If provided a promise,use
will suspend until a value is resolved.use
can only be used in render but can be called conditionally.ref
as a prop: Refs can now be used as props, removing the need forforwardRef
.React DOM Client
<form> action
prop: Form Actions allow you to manage forms automatically and integrate withuseFormStatus
. When a<form> action
succeeds, React will automatically reset the form for uncontrolled components. The form can be reset manually with the newrequestFormReset
API.<button> and <input> formAction
prop: Actions can be passed to theformAction
prop 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
.<head>
section of the document.<head>
on the client before revealing the content of a Suspense boundary that depends on that stylesheet.preinit
,preload
,prefetchDNS
, andpreconnect
APIs 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
prerender
andprerenderToNodeStream
APIs 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
Deprecations
element.ref
access: React 19 supports ref as a prop, so we’re deprecatingelement.ref
in 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 @testing-library/react or @testing-library/react-nativeBreaking 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
onUncaughtError
andonCaughtError
methods tocreateRoot
andhydrateRoot
to customize this error handling.propTypes
: UsingpropTypes
will now be silently ignored. If required, we recommend migrating to TypeScript or another type-checking solution.defaultProps
for functions: ES6 default parameters can be used in place. Class components continue to supportdefaultProps
since there is no ES6 alternative.contextTypes
andgetChildContext
: Legacy Context for class components has been removed in favor of thecontextType
API.React.createFactory
: Now that JSX is broadly supported, allcreateFactory
usage can be migrated to JSX components.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 @testing-library/react or @testing-library/react-native instead.React DOM
react-dom/test-utils
: We’ve movedact
fromreact-dom/test-utils
to react. All other utilities have been removed.ReactDOM
.render
,ReactDOM
.hydrate
: These have been removed in favor of the concurrent equivalents:ReactDOM
.createRoot
andReactDOM.hydrateRoot
.unmountComponentAtNode
: Removed in favor ofroot.unmount()
.ReactDOM
.findDOMNode
: You can replaceReactDOM
.findDOMNode
with DOM Refs.Notable Changes
React
<Context>
as a provider: You can now render<Context>
as a provider instead of<Context.Provider>
.useDeferredValue
initial value argument: When provided,useDeferredValue
will return the initial value for the initial render of a component, then schedule a re-render in the background with thedeferredValue
returned.useMemo
anduseCallback
will 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.React DOM
TypeScript Changes
The most common changes can be codemodded with
npx types-react-codemod@latest preset-19 ./path-to-your-react-ts-files
.ReactChild
(replacement:React.ReactElement | number | string)
ReactFragment
(replacement:Iterable<React.ReactNode>
)ReactNodeArray
(replacement:ReadonlyArray<React.ReactNode>
)ReactText
(replacement:number | string
)VoidFunctionComponent
(replacement:FunctionComponent
)VFC
(replacement:FC
)prop-types
:Requireable
,ValidationMap
,Validator
,WeakValidationMap
create-react-class
:ClassicComponentClass
,ClassicComponent
,ClassicElement
,ComponentSpec
,Mixin
,ReactChildren
,ReactHTML
,ReactSVG
,SFCFactory
useRef
: The initial argument is now required to matchuseState
,createContext
etcuseRef()
are now always mutable instead of sometimes being immutable. This feature was too confusing for users and conflicted with legit cases where refs were managed by React and manually written to.ReactElement
typing: The props of React elements now default tounknown
instead ofany
if the element is typed asReactElement
JSX
namespace is removed to improve interoperability with other libraries using JSX. Instead, the JSX namespace is available from the React package:import { JSX } from 'react'
useReducer
typings: MostuseReducer
usage should not require explicit type arguments.For example,
All Changes
React
useActionState()
hook to update state based on the result of a Form Action (#27270, #27278, #27309, #27302, #27307, #27366, #27370, #27321, #27374, #27372, #27397, #27399, #27460, #28557, #27570, #27571, #28631, #28788, #29694, #29695, #29694, #29665, #28232, #28319 by @acdlite, @eps1lon, and @rickhanlonii)use()
API to read resources in render (#25084, #25202, #25207, #25214, #25226, #25247, #25539, #25538, #25537, #25543, #25561, #25620, #25615, #25922, #25641, #25634, #26232, #26536, #26739, #28233 by @acdlite, @MofeiZ, @sebmarkbage, @sophiebits, @eps1lon, and @hansottowirtz)useOptimistic()
hook to display mutated state optimistically during an async mutation (#26740, #26772, #27277, #27453, #27454, #27936 by @acdlite)initialValue
argument touseDeferredValue()
hook (#27500, #27509, #27512, #27888, #27550 by @acdlite)element.ref
access (#28348, #28464, #28731 by @acdlite)<Context>
to mean<Context.Provider>
(#28226 by @gaearon)info
,group
, andgroupCollapsed
in StrictMode logging (#25172 by @timneutkens)useSyncExternalStore()
hydration in StrictMode (#26791 by @sophiebits)componentWillUnmount()
in StrictMode (#26842 by @tyao1)useState()
anduseReducer()
initializer functions in StrictMode (#28248 by @eps1lon)useId()
in StrictMode (#25713 by @gnoff)act()
no longer checksshouldYield
which can be inaccurate in test environments (#26317 by @acdlite)react.element
symbol toreact.transitional.element
(#28813 by @sebmarkbage)useSyncExternalStore()
re-render (#27199 by @acdlite)useSyncExternalStore()
dropped update when state is dispatched in render phase (#25578 by @pandaiolo)RefreshRuntime.findAffectedHostInstances
(#30538 by @gaearon)cache()
API (#27977, #28250 by @acdlite and @gnoff)propTypes
(#28324, #28326 by @gaearon)defaultProps
support, except for classes (#28733 by @acdlite)createFactory
(#27798 by @kassens)React DOM
useFormStatus()
hook to provide status information of the last form submission (#26719, #26722, #26788, #29019, #28728, #28413 by @acdlite and @eps1lon)preinit
,preinitModule
,preconnect
,prefetchDNS
,preload
, andpreloadModule
APIs.fetchPriority
to<img>
and<link>
(#25927 by @styfle)transformOrigin
prop (#26130 by @arav-ind)onScrollEnd
event (#26789 by @devongovett)<hr>
as child of<select>
(#27632 by @SouSingh)inert
(#24730 by @eps1lon)imageSizes
andimageSrcSet
(#22550 by @eps1lon)flushSync
exhausts queue even if something throws (#26366 by @acdlite)react
andreact-dom
versions don’t match (#29236 by @acdlite)srcset
andsrc
are assigned last on<img>
instances (#30340 by @gnoff)src
andhref
attributes (unless for<a href=”” />
) (#18513, #28124 by @bvaughn and @eps1lon)scale
style property (#25601 by @JonnyBurger)onChange
error message for controlled<select>
(#27740 by @Biki-das)render
,hydrate
,findDOMNode
,unmountComponentAtNode
,unstable_createEventHandle
,unstable_renderSubtreeIntoContainer
, andunstable_runWithPriority
. MovecreateRoot
andhydrateRoot
toreact-dom/client
. (#28271 by @gnoff)test-utils
(#28541 by @eps1lon)unstable_flushControlled
(#26397 by @kassens)renderToStaticNodeStream()
(#28873 by @gnoff)unstable_renderSubtreeIntoContainer
(#29771 by @kassens)React DOM Server
bootstrapScripts
andbootstrapModules
(#25104 by @gnoff)bootstrapModules
,bootstrapScripts
, and update priority queue (#26754, #26753, #27190, #27189 by @gnoff)onHeaders
entrypoint option (#27641, #27712 by @gnoff)<style>
and<script>
textContent to enable rendering inner content without dangerouslySetInnerHTML (#28870, #28871 by @gnoff)srcset
to trigger load event on mount (#30351 by @gnoff)onError
(#27761, #27850 by @gnoff and @sebmarkbage)crossorigin
support to bootstrap scripts (#26844 by @HenriqueLimas)nonce
andfetchpriority
in preload links (#26826 by @liuyenwei)referrerPolicy
toReactDOM.preload()
(#27096 by @styfle)react/jsx-dev-runtime
(#28921 by @himself65)errorInfo.digest
fromonRecoverableError
(#28222 by @gnoff)ReactTestRenderer
react-test-renderer
on web (#27903, #28904 by @jackpope and @acdlite)react-test-renderer/shallow
export (#25475, #28497 by @sebmarkbage and @jackpope)React Reconciler
prepareUpdate
(#26583, #27409 by @sebmarkbage and @sophiebits)React-Is
isConcurrentMode
andisAsyncMode
methods (#28224 by @gaearon)useSyncExternalStore
Configuration
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