## 19.3.0 (September 9, 2026)

### New React Features

- `<ViewTransition />`: Adds `<ViewTransition />` and `addTransitionType` APIs to power View Transition animations in React (@sebmarkbage, @jackpope, @gaearon: [#31975](https://github.com/facebook/react/pull/31975), [#31987](https://github.com/facebook/react/pull/31987), [#31996](https://github.com/facebook/react/pull/31996), [#31999](https://github.com/facebook/react/pull/31999), [#32001](https://github.com/facebook/react/pull/32001), [#32002](https://github.com/facebook/react/pull/32002), [#32028](https://github.com/facebook/react/pull/32028), [#32029](https://github.com/facebook/react/pull/32029), [#32031](https://github.com/facebook/react/pull/32031), [#32034](https://github.com/facebook/react/pull/32034), [#32038](https://github.com/facebook/react/pull/32038), [#32041](https://github.com/facebook/react/pull/32041), [#32050](https://github.com/facebook/react/pull/32050), [#32090](https://github.com/facebook/react/pull/32090), [#32105](https://github.com/facebook/react/pull/32105), [#32254](https://github.com/facebook/react/pull/32254), [#32379](https://github.com/facebook/react/pull/32379), [#32422](https://github.com/facebook/react/pull/32422), [#32462](https://github.com/facebook/react/pull/32462), [#32540](https://github.com/facebook/react/pull/32540), [#32545](https://github.com/facebook/react/pull/32545), [#32585](https://github.com/facebook/react/pull/32585), [#32599](https://github.com/facebook/react/pull/32599), [#32611](https://github.com/facebook/react/pull/32611), [#32612](https://github.com/facebook/react/pull/32612), [#32617](https://github.com/facebook/react/pull/32617), [#32651](https://github.com/facebook/react/pull/32651), [#32653](https://github.com/facebook/react/pull/32653), [#32656](https://github.com/facebook/react/pull/32656), [#32664](https://github.com/facebook/react/pull/32664), [#32699](https://github.com/facebook/react/pull/32699), [#32723](https://github.com/facebook/react/pull/32723), [#32734](https://github.com/facebook/react/pull/32734), [#32751](https://github.com/facebook/react/pull/32751), [#32752](https://github.com/facebook/react/pull/32752), [#32760](https://github.com/facebook/react/pull/32760), [#32761](https://github.com/facebook/react/pull/32761), [#32764](https://github.com/facebook/react/pull/32764), [#32772](https://github.com/facebook/react/pull/32772), [#32790](https://github.com/facebook/react/pull/32790), [#32819](https://github.com/facebook/react/pull/32819), [#32820](https://github.com/facebook/react/pull/32820), [#32822](https://github.com/facebook/react/pull/32822), [#32833](https://github.com/facebook/react/pull/32833), [#32849](https://github.com/facebook/react/pull/32849), [#33094](https://github.com/facebook/react/pull/33094), [#33191](https://github.com/facebook/react/pull/33191), [#33200](https://github.com/facebook/react/pull/33200), [#33206](https://github.com/facebook/react/pull/33206), [#33293](https://github.com/facebook/react/pull/33293), [#33330](https://github.com/facebook/react/pull/33330), [#33331](https://github.com/facebook/react/pull/33331), [#33332](https://github.com/facebook/react/pull/33332), [#33357](https://github.com/facebook/react/pull/33357), [#33362](https://github.com/facebook/react/pull/33362), [#33433](https://github.com/facebook/react/pull/33433), [#33576](https://github.com/facebook/react/pull/33576), [#34374](https://github.com/facebook/react/pull/34374), [#34450](https://github.com/facebook/react/pull/34450), [#34481](https://github.com/facebook/react/pull/34481), [#34500](https://github.com/facebook/react/pull/34500), [#34502](https://github.com/facebook/react/pull/34502), [#34510](https://github.com/facebook/react/pull/34510), [#34511](https://github.com/facebook/react/pull/34511), [#34539](https://github.com/facebook/react/pull/34539), [#35567](https://github.com/facebook/react/pull/35567), [#35564](https://github.com/facebook/react/pull/35564), [#35485](https://github.com/facebook/react/pull/35485), [#35380](https://github.com/facebook/react/pull/35380), [#35063](https://github.com/facebook/react/pull/35063), [#35060](https://github.com/facebook/react/pull/35060), [#34676](https://github.com/facebook/react/pull/34676), [#36917](https://github.com/facebook/react/pull/36917), [#35337](https://github.com/facebook/react/pull/35337), [#35520](https://github.com/facebook/react/pull/35520))
- Fragment Refs: Add Refs to `<Fragment />` to support composable platform behavior (@jackpope, @sebmarkbage, @eps1lon, @Dhakshin2007, @chirokas, @teamleaderleo, @fallintoplace: [#32465](https://github.com/facebook/react/pull/32465), [#32613](https://github.com/facebook/react/pull/32613), [#32619](https://github.com/facebook/react/pull/32619), [#32654](https://github.com/facebook/react/pull/32654), [#32660](https://github.com/facebook/react/pull/32660), [#32682](https://github.com/facebook/react/pull/32682), [#32722](https://github.com/facebook/react/pull/32722), [#32813](https://github.com/facebook/react/pull/32813), [#32814](https://github.com/facebook/react/pull/32814), [#33056](https://github.com/facebook/react/pull/33056), [#33058](https://github.com/facebook/react/pull/33058), [#33093](https://github.com/facebook/react/pull/33093), [#34069](https://github.com/facebook/react/pull/34069), [#34103](https://github.com/facebook/react/pull/34103), [#34544](https://github.com/facebook/react/pull/34544), [#34545](https://github.com/facebook/react/pull/34545), [#37062](https://github.com/facebook/react/pull/37062), [#37061](https://github.com/facebook/react/pull/37061), [#37060](https://github.com/facebook/react/pull/37060), [#36047](https://github.com/facebook/react/pull/36047), [#36010](https://github.com/facebook/react/pull/36010), [#35642](https://github.com/facebook/react/pull/35642), [#35641](https://github.com/facebook/react/pull/35641), [#35637](https://github.com/facebook/react/pull/35637), [#35630](https://github.com/facebook/react/pull/35630), [#34935](https://github.com/facebook/react/pull/34935), [#37457](https://github.com/facebook/react/pull/37457), [#37408](https://github.com/facebook/react/pull/37408), [#37326](https://github.com/facebook/react/pull/37326), [#37251](https://github.com/facebook/react/pull/37251), [#37171](https://github.com/facebook/react/pull/37171), [#37169](https://github.com/facebook/react/pull/37169), [#37168](https://github.com/facebook/react/pull/37168), [#37167](https://github.com/facebook/react/pull/37167), [#37166](https://github.com/facebook/react/pull/37166), [#37165](https://github.com/facebook/react/pull/37165), [#37164](https://github.com/facebook/react/pull/37164), [#37163](https://github.com/facebook/react/pull/37163), [#37162](https://github.com/facebook/react/pull/37162), [#37161](https://github.com/facebook/react/pull/37161), [#37160](https://github.com/facebook/react/pull/37160), [#37125](https://github.com/facebook/react/pull/37125), [#37063](https://github.com/facebook/react/pull/37063))

### New React DOM Features

- `browser()`: a new `react-dom` API that returns a usable which errors during server rendering and resolves in the browser. `use(browser())` inside a `<Suspense>` boundary marks a subtree as browser-only without reporting a recoverable error (@gnoff: [#37143](https://github.com/facebook/react/pull/37143), [#37241](https://github.com/facebook/react/pull/37241))
  - Added an `onBrowserBailout` option to the `react-dom/server` APIs to observe when a subtree defers to the browser (@gnoff [#37193](https://github.com/facebook/react/pull/37193))

### Notable changes

- Enable Trusted Types API integration (@rickhanlonii [#35816](https://github.com/facebook/react/pull/35816))
- Transitions now render independently instead of being entangled into a single render, so a slow transition no longer holds up unrelated ones (@acdlite [#37290](https://github.com/facebook/react/pull/37290))
- Added a DEV-only warning when a component appears to have been unblocked by calling `use()` conditionally (@hoxyq, @eps1lon: [#37104](https://github.com/facebook/react/pull/37104), [#37203](https://github.com/facebook/react/pull/37203), [#37491](https://github.com/facebook/react/pull/37491))

### All Changes

#### React

- Fast Refresh Fixes
  - Fix Fast Refresh to find and remount edits to components wrapped behind `lazy()` (@sophiebits [#36965](https://github.com/facebook/react/pull/36965))
  - Fix Fast Refresh so edits to a `memo()` comparison function take effect (@sophiebits [#36964](https://github.com/facebook/react/pull/36964))
  - Fix Fast Refresh crash when an edit changes the kind of a component's type (@sophiebits [#36963](https://github.com/facebook/react/pull/36963))
  - Unify hot reload type resolution for Fast Refresh (@sophiebits [#36962](https://github.com/facebook/react/pull/36962))
  - Fix Fast Refresh to remount correctly when an edit changes the component kind (@sophiebits [#36950](https://github.com/facebook/react/pull/36950))
  - Double invoke effects in StrictMode after Fast Refresh (@eps1lon [#35962](https://github.com/facebook/react/pull/35962))
- Performance Track Fixes
  - Prevent crash when accessing `$$typeof` in Performance Tracks (@eps1lon [#35679](https://github.com/facebook/react/pull/35679))
  - Handle non-string function names in Performance Tracks (@eps1lon [#35659](https://github.com/facebook/react/pull/35659))
  - Use minus (`-`) instead of en dash for removed props in Performance Tracks (@eps1lon [#35649](https://github.com/facebook/react/pull/35649))
  - Handle arrays with bigints in deep objects in Performance Tracks (@eps1lon [#35648](https://github.com/facebook/react/pull/35648))
  - Don't enumerate typed array props in Performance Tracks in DEV (@UditDewan [#36913](https://github.com/facebook/react/pull/36913))
  - Bail out of diffing wide objects and arrays in Performance Tracks (@eps1lon [#34742](https://github.com/facebook/react/pull/34742))
  - Clear potentially large performance measures in DEV (@hoxyq [#34803](https://github.com/facebook/react/pull/34803))
  - Fix missing else branch for renders with no props change in Performance Tracks (@hoxyq [#34837](https://github.com/facebook/react/pull/34837))
- Activity Fixes
  - Fix `useSyncExternalStore` missing store mutations that happened while an Activity tree was hidden (@sophiebits [#36947](https://github.com/facebook/react/pull/36947))
  - Hide portal contents when an Activity is hidden (@acdlite [#35091](https://github.com/facebook/react/pull/35091))
  - Prevent metadata hoisting in hidden `<Activity>` trees (@ronnakamoto [#34983](https://github.com/facebook/react/pull/34983))
  - Prevent errors thrown inside a hidden Activity from escaping to the visible UI (@acdlite [#35074](https://github.com/facebook/react/pull/35074))
  - Don't unhide a node if a direct parent Offscreen is still hidden (@sebmarkbage [#34821](https://github.com/facebook/react/pull/34821))
  - Don't show internal `<Offscreen>` component in error messages (@rickhanlonii [#35763](https://github.com/facebook/react/pull/35763))
- Warn in DEV when a component appears to have been unblocked by a conditional `use()` (@hoxyq, @eps1lon: [#37104](https://github.com/facebook/react/pull/37104), [#37203](https://github.com/facebook/react/pull/37203), [#37491](https://github.com/facebook/react/pull/37491))
- Render transitions independently instead of entangling them into a single render (@acdlite [#37290](https://github.com/facebook/react/pull/37290))
- Fix hang when updating a dehydrated boundary inside a hidden tree (@gaearon [#37135](https://github.com/facebook/react/pull/37135))
- Don't reacquire Host Singletons during dev effect validation (@gnoff [#37113](https://github.com/facebook/react/pull/37113))
- Only remove properties from Host Singletons on release (@gnoff [#37112](https://github.com/facebook/react/pull/37112))
- Don't invoke effects on moved children in StrictMode (@sophiebits [#36948](https://github.com/facebook/react/pull/36948))
- Throw a clearer error when a rejected Promise is incorrectly instrumented (@eps1lon [#36328](https://github.com/facebook/react/pull/36328))
- Fix context propagation into Suspense fallbacks (@acdlite [#36160](https://github.com/facebook/react/pull/36160))
- Fix context propagation through suspended Suspense boundaries (@acdlite [#35839](https://github.com/facebook/react/pull/35839))
- Fix `useDeferredValue` getting stuck (@gaearon [#36134](https://github.com/facebook/react/pull/36134))
- Update `useActionState` error message to say "action state" instead of "form state" (@rickhanlonii [#35790](https://github.com/facebook/react/pull/35790))
- Don't warn when rendering data block scripts (@eps1lon [#35953](https://github.com/facebook/react/pull/35953))
- Treat fibers with alternates as mounted in `getNearestMountedFiber` (@sebmarkbage [#35578](https://github.com/facebook/react/pull/35578))
- Always instrument the lazy initializer thenable (@gnoff [#35521](https://github.com/facebook/react/pull/35521))
- Annotate cascading updates for DevTools performance tracks in DEV (@huntie [#34961](https://github.com/facebook/react/pull/34961))
- Resolve the `.default` export of a `React.lazy` as the canonical value (@sebmarkbage [#34906](https://github.com/facebook/react/pull/34906))
- Limit owner stacks to 10 frames (@eps1lon [#34864](https://github.com/facebook/react/pull/34864))
- Ensure `useEffectEvent` reads latest values in `forwardRef` and `memo()` components (@eps1lon [#34831](https://github.com/facebook/react/pull/34831))

#### React DOM

- Copy `source` onto the synthetic `toggle` event (@lazerg [#37389](https://github.com/facebook/react/pull/37389))
- Update HTML parser rules for the new `<select>` parser (@josepharhar [#34804](https://github.com/facebook/react/pull/34804))
- Update `defaultValue` for `type="number"` inputs to match other input types (@sophiebits [#36980](https://github.com/facebook/react/pull/36980))
- Avoid setting `innerHTML` when it hasn't changed (@sophiebits [#36949](https://github.com/facebook/react/pull/36949))
- Forward the `nonce` option in `ReactDOM.preloadModule()` (@UditDewan [#36851](https://github.com/facebook/react/pull/36851))
- Support `fetchPriority` for module resources (@TheAlexLichter [#36835](https://github.com/facebook/react/pull/36835))
- Track stylesheet preloads when explicitly preloaded to avoid unnecessary suspension (@gnoff [#36386](https://github.com/facebook/react/pull/36386))
- Suggest correct casing for the misspelled `credentialless` iframe attribute (@vmx906 [#36322](https://github.com/facebook/react/pull/36322))
- Add `credentialless` as a recognized boolean attribute for iframes (@vmx906 [#36148](https://github.com/facebook/react/pull/36148))
- Prevent reentrant `finishedTask` from calling `completeAll` multiple times (@gnoff [#36287](https://github.com/facebook/react/pull/36287))
- Update the CSS shorthand property list (@kidonng [#35636](https://github.com/facebook/react/pull/35636))
- Support the `maskType` SVG prop (@sleitor [#35921](https://github.com/facebook/react/pull/35921))
- Add support for `onFullscreenChange` and `onFullscreenError` events (@chirokas [#34621](https://github.com/facebook/react/pull/34621))
- Include `submitter` in `submit` events (@eps1lon [#35590](https://github.com/facebook/react/pull/35590))
- Fire `onReset` when automatically resetting forms (@eps1lon [#35176](https://github.com/facebook/react/pull/35176))
- Use the `FormData` `submitter` parameter (@jenseng [#29028](https://github.com/facebook/react/pull/29028))
- Fix form status reset when component state is updated (@eps1lon [#34075](https://github.com/facebook/react/pull/34075))
- Batch updates from `resize` events until the next frame (@eps1lon [#35117](https://github.com/facebook/react/pull/35117))

#### React Server

- Add `nonce` to rendered import maps (@mattcosta7 [#37339](https://github.com/facebook/react/pull/37339))
- Add an `onBrowserBailout` option to observe subtrees that defer to the browser (@gnoff [#37193](https://github.com/facebook/react/pull/37193))
- Stop the caller's signal from retaining a finished render (@unstubbable [#37315](https://github.com/facebook/react/pull/37315))
- Construct the render lifetime controller only when it is needed (@unstubbable [#37357](https://github.com/facebook/react/pull/37357))
- Fix `react-dom/server` hanging on Deno (@fraidev [#35235](https://github.com/facebook/react/pull/35235))
- Extend stack overflow recovery to retries in SSR (@jackpope [#36977](https://github.com/facebook/react/pull/36977))
- Fix false-positive hydration mismatch on `nonce` attributes (@MaxwellCohen [#37030](https://github.com/facebook/react/pull/37030))
- Guard shell-error callbacks instead of nulling them out on the request (@eps1lon [#36916](https://github.com/facebook/react/pull/36916))
- Stop firing `onAllReady` after the shell errored (@eps1lon [#36903](https://github.com/facebook/react/pull/36903))
- Treat an incomplete tree as an error during error recovery (@acdlite [#36911](https://github.com/facebook/react/pull/36911))
- Fix non-script `modulepreload` tracking (@fallintoplace [#36564](https://github.com/facebook/react/pull/36564))
- Finalize postponed `nextSegmentId` after the prelude flush (@gaojude [#36779](https://github.com/facebook/react/pull/36779))
- Preserve `referrerPolicy` in image preload headers (@ulises-jeremias [#36803](https://github.com/facebook/react/pull/36803))
- Allow pending work to specialize abort reasons (@gnoff [#36586](https://github.com/facebook/react/pull/36586))
- Abort tasks that suspend after aborting during render (@gnoff [#36585](https://github.com/facebook/react/pull/36585))
- Finish abort in a scheduled task (@gnoff [#36580](https://github.com/facebook/react/pull/36580))
- Fix aborts during resumed rendering (@gnoff [#36584](https://github.com/facebook/react/pull/36584))
- Track abort state on the request (@gnoff [#36583](https://github.com/facebook/react/pull/36583))
- Model external work scheduling explicitly in the fb bundle (@gnoff [#36576](https://github.com/facebook/react/pull/36576))
- Continue reporting aborted task errors after a fatal abort (@gnoff [#36575](https://github.com/facebook/react/pull/36575))
- Disallow abort reentrancy (@gnoff [#36574](https://github.com/facebook/react/pull/36574))
- Stop transpiling computed property names (@eps1lon [#36542](https://github.com/facebook/react/pull/36542))
- Fix crash when capturing the callsite of a stalled `use()` of a rejected Flight chunk (@lubieowoce [#36544](https://github.com/facebook/react/pull/36544))
- Double invoke effects in Strict Mode during hydration (@eps1lon [#35961](https://github.com/facebook/react/pull/35961))
- Add additional task reentrancy protections in Fizz (@gnoff [#36291](https://github.com/facebook/react/pull/36291))
- Don't outline Suspense boundaries with suspensey CSS during shell flush (@gnoff [#35824](https://github.com/facebook/react/pull/35824))
- Push a stalled `use()` to the owner stack and debug task (@eps1lon [#35226](https://github.com/facebook/react/pull/35226))
- Fix `useId` tracking on replay (@gnoff [#35518](https://github.com/facebook/react/pull/35518))
- Correctly handle replaying when hydrating (@gnoff [#35494](https://github.com/facebook/react/pull/35494))
- Simplify the `createSuspenseBoundary` path (@sebmarkbage [#35087](https://github.com/facebook/react/pull/35087))
- Unify preamble-only fields to save a field on Suspense boundaries (@sebmarkbage [#35068](https://github.com/facebook/react/pull/35068))
- Unify prerender-only fields to save a field on Suspense boundaries (@sebmarkbage [#35067](https://github.com/facebook/react/pull/35067))
- Push halted awaits to the owner stack for late-arriving I/O info (@unstubbable [#35019](https://github.com/facebook/react/pull/35019))
- Include all Node.js APIs in the Bun entrypoint for `react-dom/server` (@RiskyMH [#34193](https://github.com/facebook/react/pull/34193))
- Detach a Suspense boundary after flushing its segment (@gnoff [#34694](https://github.com/facebook/react/pull/34694))

#### React Server Components

- Keep an element pending while a referenced row is resolving (@unstubbable [#37542](https://github.com/facebook/react/pull/37542))
- Fix `RangeError` from exponential debug info growth (@unstubbable [#37481](https://github.com/facebook/react/pull/37481))
- Abort the cache signal when debug objects are retained (@unstubbable [#37342](https://github.com/facebook/react/pull/37342))
- Transfer key validation of lazy nodes when they are unwrapped (@unstubbable [#37258](https://github.com/facebook/react/pull/37258))
- Add `pending_weak` to the Flight thenable protocol (@acdlite [#37154](https://github.com/facebook/react/pull/37154))
- Outline and dedupe repeated strings (@gaearon [#37147](https://github.com/facebook/react/pull/37147))
- Port Reply Server traversal guards to the Flight Client (@eps1lon [#37144](https://github.com/facebook/react/pull/37144))
- Define Flight chunk `.then` with `Object.defineProperty` (@eps1lon [#37109](https://github.com/facebook/react/pull/37109))
- Support Turbopack's experimental array format for chunks (@sampoder [#37095](https://github.com/facebook/react/pull/37095))
- Limit fake JSX call site stacks to 10 frames (@timneutkens [#37086](https://github.com/facebook/react/pull/37086))
- Improve performance when decoding Flight replies (@gnoff [#37090](https://github.com/facebook/react/pull/37090))
- Recognize Node 22+ V8 frames for `Promise` statics in debug info (@gaearon [#36969](https://github.com/facebook/react/pull/36969))
- Tailor the warning for binary data serialized through `toJSON` (Node `Buffer`) (@unstubbable [#36873](https://github.com/facebook/react/pull/36873))
- Resolve models before `JSON.stringify` for faster serialization (@mhart [#36795](https://github.com/facebook/react/pull/36795))
- Prune debug info when chunks error (@gnoff [#36782](https://github.com/facebook/react/pull/36782))
- Avoid main-thread stalls from large debug strings (@unstubbable [#36570](https://github.com/facebook/react/pull/36570))
- Fix stranded row content under Node stream backpressure (@unstubbable [#36516](https://github.com/facebook/react/pull/36516))
- Fix dropped `FormData` entries in `decodeReplyFromBusboy` (@unstubbable [#36468](https://github.com/facebook/react/pull/36468))
- Harden types and improve performance of Flight replies (@eps1lon [#36425](https://github.com/facebook/react/pull/36425))
- Add more cycle protections to Flight replies (@eps1lon [#36236](https://github.com/facebook/react/pull/36236))
- Transport `AggregateError.errors` (@eps1lon [#36156](https://github.com/facebook/react/pull/36156))
- Bail out early when a backing entry for `Blob` deserialization is not a `Blob` (@eps1lon [#36055](https://github.com/facebook/react/pull/36055))
- Clear chunk reason after successful module initialization (@unstubbable [#36024](https://github.com/facebook/react/pull/36024))
- Add support for transporting `Error.cause` (@eps1lon [#35810](https://github.com/facebook/react/pull/35810))
- Walk parsed JSON instead of using a reviver for faster RSC payload parsing (@timneutkens [#35776](https://github.com/facebook/react/pull/35776))
- Skip `transferReferencedDebugInfo` during debug info resolution (@unstubbable [#35795](https://github.com/facebook/react/pull/35795))
- Add `unstable_allowPartialStream` option to Flight Client (@unstubbable [#35731](https://github.com/facebook/react/pull/35731))
- Fix `encodeReply` for JSX with temporary references (@unstubbable [#35730](https://github.com/facebook/react/pull/35730))
- Fix debug channel flag in Node.js `renderToPipeableStream` (@feedthejim [#35724](https://github.com/facebook/react/pull/35724))
- Fix stack overflow in `visitAsyncNode` with deep async chains (@unstubbable [#35612](https://github.com/facebook/react/pull/35612))
- Allow Server Components to render context providers from client modules (@rickhanlonii [#35675](https://github.com/facebook/react/pull/35675))
- Allow overriding `request.timeOrigin` via `options.startTime` (@lubieowoce [#35598](https://github.com/facebook/react/pull/35598))
- Warn once if `eval` is disabled in the dev environment (@eps1lon [#35661](https://github.com/facebook/react/pull/35661))
- Restore original function name in dev server callstacks served with `unsafe-eval` (@eps1lon [#35650](https://github.com/facebook/react/pull/35650))
- Fix `react-markup` types for server references (@eps1lon [#35634](https://github.com/facebook/react/pull/35634))
- Add more DoS mitigations to Flight replies and harden Flight (@unstubbable [#35632](https://github.com/facebook/react/pull/35632))
- Allow cyclic references to be serialized when unwrapping lazy elements (@unstubbable [#35471](https://github.com/facebook/react/pull/35471))
- Improve cyclic thenable detection in Flight reply server (@cvan20191 [#35369](https://github.com/facebook/react/pull/35369))
- Add extra loop protection to Flight reply server (@sebmarkbage [#35351](https://github.com/facebook/react/pull/35351))
- Patch Promise cycles and `toString` on Server Functions (@sebmarkbage [#35345](https://github.com/facebook/react/pull/35345))
- Move `react-server-dom-webpack/*.unbundled` to private `react-server-dom-unbundled` (@eps1lon [#35290](https://github.com/facebook/react/pull/35290))
- Never parse `then` functions in Flight replies (@sebmarkbage [#35289](https://github.com/facebook/react/pull/35289))
- Patch Flight reply server with fixes from Flight Client (@sebmarkbage [#35277](https://github.com/facebook/react/pull/35277))
- Complete the list of Node.js internal Promise awaits (@eps1lon [#35161](https://github.com/facebook/react/pull/35161))
- Reduce risk of maximum call stack exceeded when emitting async sequences (@eps1lon [#35159](https://github.com/facebook/react/pull/35159))
- Fix pending chunks count for streams and async iterables in DEV (@unstubbable [#35143](https://github.com/facebook/react/pull/35143))
- Fix broken byte stream parsing caused by buffer detachment (@unstubbable [#35127](https://github.com/facebook/react/pull/35127))
- Fix `hasReadable` flag in Node.js clients' debug channel (@unstubbable [#35039](https://github.com/facebook/react/pull/35039))
- Fix debug info filtering to include later resolved I/O (@unstubbable [#35036](https://github.com/facebook/react/pull/35036))
- Cache the value when visiting the same I/O or Promise along different paths (@sebmarkbage [#35005](https://github.com/facebook/react/pull/35005))
- Clone subsequent I/O nodes when resolved more than once (@sebmarkbage [#35003](https://github.com/facebook/react/pull/35003))
- Fix hang after resolving cyclic references (@unstubbable [#34988](https://github.com/facebook/react/pull/34988))
- Allow passing DEV-only `startTime` as an option (@sebmarkbage [#34912](https://github.com/facebook/react/pull/34912))
- Ignore bound-anonymous-fn resources as they're not considered I/O (@sebmarkbage [#34911](https://github.com/facebook/react/pull/34911))
- Fix detached `ArrayBuffer` error when streaming typed arrays (@unstubbable [#34849](https://github.com/facebook/react/pull/34849))
- Exclude RSC stream if the stream resolves in a task (@sebmarkbage [#34838](https://github.com/facebook/react/pull/34838))
- Forward the current environment when forwarding I/O entries (@sebmarkbage [#34836](https://github.com/facebook/react/pull/34836))
- Look for moved debug info when logging component performance track (@sebmarkbage [#34839](https://github.com/facebook/react/pull/34839))
- Respect `displayName` of Promise instances on the server (@sebmarkbage [#34825](https://github.com/facebook/react/pull/34825))
- Avoid unnecessary indirection when serializing debug info (@unstubbable [#34797](https://github.com/facebook/react/pull/34797))
- Fix preload `as` attribute for stylesheets (@unstubbable [#34760](https://github.com/facebook/react/pull/34760))
- Don't serialize `toJSON` in debug path and omit wide arrays (@sebmarkbage [#34759](https://github.com/facebook/react/pull/34759))
- Add support for `<Activity>` (@eps1lon [#34697](https://github.com/facebook/react/pull/34697))

## 19.2.7 (June 1, 2026)

### React Server Components

- Fixed missing `FormData` entries in Server Actions which regressed in 19.2.6 (@unstubbable [#36566](https://github.com/facebook/react/pull/36566))

## 19.2.6 (May 6, 2026)

### React Server Components

- Type hardening and performance improvements (@eps1lon, @unstubbable [#36425](https://github.com/facebook/react/pull/36425))

## 19.2.5 (March 18, 2026)

### React Server Components

- Add more cycle protections (@eps1lon, @unstubbable [#36236](https://github.com/facebook/react/pull/36236))

## 19.2.4 (Jan 26, 2026)

### React Server Components

- Add more DoS mitigations to Server Actions, and harden Server Components (@gnoff, @lubieowoce, @sebmarkbage, @unstubbable [#35632](https://github.com/facebook/react/pull/35632))

## 19.2.3 (Dec 11, 2025)

### React Server Components

- Add extra loop protection to React Server Functions (@sebmarkbage [#35351](https://github.com/facebook/react/pull/35351))

## 19.2.2 (Dec 11, 2025)

### React Server Components

- Move `react-server-dom-webpack/*.unbundled` to private `react-server-dom-unbundled` (@eps1lon [#35290](https://github.com/facebook/react/pull/35290))
- Patch Promise cycles and toString on Server Functions (@sebmarkbage, @unstubbable [#35289](https://github.com/facebook/react/pull/35289), [#35345](https://github.com/facebook/react/pull/35345))

## 19.2.1 (Dec 3, 2025)

### React Server Components

- Bring React Server Component fixes to Server Actions (@sebmarkbage [#35277](https://github.com/facebook/react/pull/35277))

## 19.2.0 (October 1st, 2025)

Below is a list of all new features, APIs, and bug fixes.

Read the [React 19.2 release post](https://react.dev/blog/2025/10/01/react-19-2) for more information.

### New React Features

- [`<Activity>`](https://react.dev/reference/react/Activity): A new API to hide and restore the UI and internal state of its children.
- [`useEffectEvent`](https://react.dev/reference/react/useEffectEvent) is a React Hook that lets you extract non-reactive logic into an [Effect Event](https://react.dev/learn/separating-events-from-effects#declaring-an-effect-event).
- [`cacheSignal`](https://react.dev/reference/react/cacheSignal) (for RSCs) lets your know when the `cache()` lifetime is over.
- [React Performance tracks](https://react.dev/reference/dev-tools/react-performance-tracks) appear on the Performance panel’s timeline in your browser developer tools

### New React DOM Features

- Added resume APIs for partial pre-rendering with Web Streams:
  - [`resume`](https://react.dev/reference/react-dom/server/resume): to resume a prerender to a stream.
  - [`resumeAndPrerender`](https://react.dev/reference/react-dom/static/resumeAndPrerender): to resume a prerender to HTML.
- Added resume APIs for partial pre-rendering with Node Streams:
  - [`resumeToPipeableStream`](https://react.dev/reference/react-dom/server/resumeToPipeableStream): to resume a prerender to a stream.
  - [`resumeAndPrerenderToNodeStream`](https://react.dev/reference/react-dom/static/resumeAndPrerenderToNodeStream): to resume a prerender to HTML.
- Updated [`prerender`](https://react.dev/reference/react-dom/static/prerender) APIs to return a `postponed` state that can be passed to the `resume` APIs.

### Notable changes

- React DOM now batches suspense boundary reveals, matching the behavior of client side rendering. This change is especially noticeable when animating the reveal of Suspense boundaries e.g. with the upcoming `<ViewTransition>` Component. React will batch as much reveals as possible before the first paint while trying to hit popular first-contentful paint metrics.
- Add Node Web Streams (`prerender`, `renderToReadableStream`) to server-side-rendering APIs for Node.js
- Use underscore instead of `:` IDs generated by useId

### All Changes

#### React

- `<Activity />` was developed over many years, starting before `ClassComponent.setState` (@acdlite @sebmarkbage and many others)
- Stringify context as "SomeContext" instead of "SomeContext.Provider" (@kassens [#33507](https://github.com/facebook/react/pull/33507))
- Include stack of cause of React instrumentation errors with `%o` placeholder (@eps1lon [#34198](https://github.com/facebook/react/pull/34198))
- Fix infinite `useDeferredValue` loop in popstate event (@acdlite [#32821](https://github.com/facebook/react/pull/32821))
- Fix a bug when an initial value was passed to `useDeferredValue` (@acdlite [#34376](https://github.com/facebook/react/pull/34376))
- Fix a crash when submitting forms with Client Actions (@sebmarkbage [#33055](https://github.com/facebook/react/pull/33055))
- Hide/unhide the content of dehydrated suspense boundaries if they resuspend (@sebmarkbage [#32900](https://github.com/facebook/react/pull/32900))
- Avoid stack overflow on wide trees during Hot Reload (@sophiebits [#34145](https://github.com/facebook/react/pull/34145))
- Improve Owner and Component stacks in various places (@sebmarkbage, @eps1lon: [#33629](https://github.com/facebook/react/pull/33629), [#33724](https://github.com/facebook/react/pull/33724), [#32735](https://github.com/facebook/react/pull/32735), [#33723](https://github.com/facebook/react/pull/33723))
- Add `cacheSignal` (@sebmarkbage [#33557](https://github.com/facebook/react/pull/33557))

#### React DOM

- Block on Suspensey Fonts during reveal of server-side-rendered content (@sebmarkbage [#33342](https://github.com/facebook/react/pull/33342))
- Use underscore instead of `:` for IDs generated by `useId` (@sebmarkbage, @eps1lon: [#32001](https://github.com/facebook/react/pull/32001), [https://github.com/facebook/react/pull/33342](https://github.com/facebook/react/pull/33342)[#33099](https://github.com/facebook/react/pull/33099), [#33422](https://github.com/facebook/react/pull/33422))
- Stop warning when ARIA 1.3 attributes are used (@Abdul-Omira [#34264](https://github.com/facebook/react/pull/34264))
- Allow `nonce` to be used on hoistable styles (@Andarist [#32461](https://github.com/facebook/react/pull/32461))
- Warn for using a React owned node as a Container if it also has text content (@sebmarkbage [#32774](https://github.com/facebook/react/pull/32774))
- s/HTML/text for for error messages if text hydration mismatches (@rickhanlonii [#32763](https://github.com/facebook/react/pull/32763))
- Fix a bug with `React.use` inside `React.lazy`\-ed Component (@hi-ogawa [#33941](https://github.com/facebook/react/pull/33941))
- Enable the `progressiveChunkSize` option for server-side-rendering APIs (@sebmarkbage [#33027](https://github.com/facebook/react/pull/33027))
- Fix a bug with deeply nested Suspense inside Suspense fallback when server-side-rendering (@gnoff [#33467](https://github.com/facebook/react/pull/33467))
- Avoid hanging when suspending after aborting while rendering (@gnoff [#34192](https://github.com/facebook/react/pull/34192))
- Add Node Web Streams to server-side-rendering APIs for Node.js (@sebmarkbage [#33475](https://github.com/facebook/react/pull/33475))

#### React Server Components

- Preload `<img>` and `<link>` using hints before they're rendered (@sebmarkbage [#34604](https://github.com/facebook/react/pull/34604))
- Log error if production elements are rendered during development (@eps1lon [#34189](https://github.com/facebook/react/pull/34189))
- Fix a bug when returning a Temporary reference (e.g. a Client Reference) from Server Functions (@sebmarkbage [#34084](https://github.com/facebook/react/pull/34084), @denk0403 [#33761](https://github.com/facebook/react/pull/33761))
- Pass line/column to `filterStackFrame` (@eps1lon [#33707](https://github.com/facebook/react/pull/33707))
- Support Async Modules in Turbopack Server References (@lubieowoce [#34531](https://github.com/facebook/react/pull/34531))
- Add support for .mjs file extension in Webpack (@jennyscript [#33028](https://github.com/facebook/react/pull/33028))
- Fix a wrong missing key warning (@unstubbable [#34350](https://github.com/facebook/react/pull/34350))
- Make console log resolve in predictable order (@sebmarkbage [#33665](https://github.com/facebook/react/pull/33665))

#### React Reconciler

- [createContainer](https://github.com/facebook/react/blob/v19.2.0/packages/react-reconciler/src/ReactFiberReconciler.js#L255-L261) and [createHydrationContainer](https://github.com/facebook/react/blob/v19.2.0/packages/react-reconciler/src/ReactFiberReconciler.js#L305-L312) had their parameter order adjusted after `on*` handlers to account for upcoming experimental APIs

## 19.1.8 (June 1, 2026)

### React Server Components

- Fixed missing `FormData` entries in Server Actions which regressed in 19.1.7 (@unstubbable [#36567](https://github.com/facebook/react/pull/36567))

## 19.1.7 (May 6, 2026)

### React Server Components

- Type hardening and performance improvements (@eps1lon, @unstubbable [#36425](https://github.com/facebook/react/pull/36425))

## 19.1.6 (March 18, 2026)

### React Server Components

- Add more cycle protections (@eps1lon, @unstubbable [#36236](https://github.com/facebook/react/pull/36236))

## 19.1.5 (Jan 26, 2026)

### React Server Components

- Add more DoS mitigations to Server Actions, and harden Server Components (@gnoff, @lubieowoce, @sebmarkbage, @unstubbable [#35632](https://github.com/facebook/react/pull/35632))

## 19.1.4 (Dec 11, 2025)

### React Server Components

- Add extra loop protection to React Server Functions (@sebmarkbage [#35351](https://github.com/facebook/react/pull/35351))

## 19.1.3 (Dec 11, 2025)

### React Server Components

- Move `react-server-dom-webpack/*.unbundled` to private `react-server-dom-unbundled` (@eps1lon [#35290](https://github.com/facebook/react/pull/35290))
- Patch Promise cycles and toString on Server Functions (@sebmarkbage, @unstubbable [#35289](https://github.com/facebook/react/pull/35289), [#35345](https://github.com/facebook/react/pull/35345))

## 19.1.2 (Dec 3, 2025)

### React Server Components

- Bring React Server Component fixes to Server Actions (@sebmarkbage [#35277](https://github.com/facebook/react/pull/35277))

## 19.1.1 (July 28, 2025)

### React
* Fixed Owner Stacks to work with ES2015 function.name semantics ([#33680](https://github.com/facebook/react/pull/33680) by @hoxyq)

## 19.1.0 (March 28, 2025)

### Owner Stack

An Owner Stack is a string representing the components that are directly responsible for rendering a particular component. You can log Owner Stacks when debugging or use Owner Stacks to enhance error overlays or other development tools. Owner Stacks are only available in development builds. Component Stacks in production are unchanged.

* An Owner Stack is a development-only stack trace that helps identify which components are responsible for rendering a particular component. An Owner Stack is distinct from a Component Stacks, which shows the hierarchy of components leading to an error.
* The [captureOwnerStack API](https://react.dev/reference/react/captureOwnerStack) is only available in development mode and returns a Owner Stack, if available. The API can be used to enhance error overlays or log component relationships when debugging. [#29923](https://github.com/facebook/react/pull/29923), [#32353](https://github.com/facebook/react/pull/32353), [#30306](https://github.com/facebook/react/pull/30306),
[#32538](https://github.com/facebook/react/pull/32538), [#32529](https://github.com/facebook/react/pull/32529), [#32538](https://github.com/facebook/react/pull/32538)

### React
* Enhanced support for Suspense boundaries to be used anywhere, including the client, server, and during hydration. [#32069](https://github.com/facebook/react/pull/32069), [#32163](https://github.com/facebook/react/pull/32163), [#32224](https://github.com/facebook/react/pull/32224), [#32252](https://github.com/facebook/react/pull/32252)
* Reduced unnecessary client rendering through improved hydration scheduling [#31751](https://github.com/facebook/react/pull/31751)
* Increased priority of client rendered Suspense boundaries [#31776](https://github.com/facebook/react/pull/31776)
* Fixed frozen fallback states by rendering unfinished Suspense boundaries on the client. [#31620](https://github.com/facebook/react/pull/31620)
* Reduced garbage collection pressure by improving Suspense boundary retries. [#31667](https://github.com/facebook/react/pull/31667)
* Fixed erroneous “Waiting for Paint” log when the passive effect phase was not delayed [#31526](https://github.com/facebook/react/pull/31526)
* Fixed a regression causing key warnings for flattened positional children in development mode. [#32117](https://github.com/facebook/react/pull/32117)
* Updated `useId` to use valid CSS selectors, changing format from `:r123:` to `«r123»`. [#32001](https://github.com/facebook/react/pull/32001)
* Added a dev-only warning for null/undefined created in useEffect, useInsertionEffect, and useLayoutEffect. [#32355](https://github.com/facebook/react/pull/32355)
* Fixed a bug where dev-only methods were exported in production builds. React.act is no longer available in production builds. [#32200](https://github.com/facebook/react/pull/32200)
* Improved consistency across prod and dev to improve compatibility with Google Closure Compiler and bindings [#31808](https://github.com/facebook/react/pull/31808)
* Improve passive effect scheduling for consistent task yielding. [#31785](https://github.com/facebook/react/pull/31785)
* Fixed asserts in React Native when passChildrenWhenCloningPersistedNodes is enabled for OffscreenComponent rendering. [#32528](https://github.com/facebook/react/pull/32528)
* Fixed component name resolution for Portal [#32640](https://github.com/facebook/react/pull/32640)
* Added support for beforetoggle and toggle events on the dialog element. [#32479](https://github.com/facebook/react/pull/32479)

### React DOM
* Fixed double warning when the `href` attribute is an empty string [#31783](https://github.com/facebook/react/pull/31783)
 * Fixed an edge case where `getHoistableRoot()` didn’t work properly when the container was a Document [#32321](https://github.com/facebook/react/pull/32321)
* Removed support for using HTML comments (e.g. `<!-- -->`) as a DOM container. [#32250](https://github.com/facebook/react/pull/32250)
* Added support for `<script>` and `<template>` tags to be nested within `<select>` tags. [#31837](https://github.com/facebook/react/pull/31837)
* Fixed responsive images to be preloaded as HTML instead of headers [#32445](https://github.com/facebook/react/pull/32445)

### use-sync-external-store
* Added `exports` field to `package.json` for `use-sync-external-store` to support various entrypoints. [#25231](https://github.com/facebook/react/pull/25231)

### React Server Components
* Added `unstable_prerender`, a new experimental API for prerendering React Server Components on the server [#31724](https://github.com/facebook/react/pull/31724)
* Fixed an issue where streams would hang when receiving new chunks after a global error [#31840](https://github.com/facebook/react/pull/31840), [#31851](https://github.com/facebook/react/pull/31851)
* Fixed an issue where pending chunks were counted twice. [#31833](https://github.com/facebook/react/pull/31833)
* Added support for streaming in edge environments [#31852](https://github.com/facebook/react/pull/31852)
* Added support for sending custom error names from a server so that they are available in the client for console replaying. [#32116](https://github.com/facebook/react/pull/32116)
* Updated the server component wire format to remove IDs for hints and console.log because they have no return value [#31671](https://github.com/facebook/react/pull/31671)
* Exposed `registerServerReference` in client builds to handle server references in different environments. [#32534](https://github.com/facebook/react/pull/32534)
* Added react-server-dom-parcel package which integrates Server Components with the [Parcel bundler](https://parceljs.org/) [#31725](https://github.com/facebook/react/pull/31725), [#32132](https://github.com/facebook/react/pull/32132), [#31799](https://github.com/facebook/react/pull/31799), [#32294](https://github.com/facebook/react/pull/32294), [#31741](https://github.com/facebook/react/pull/31741)

## 19.0.7 (June 1, 2026)

### React Server Components

- Fixed missing `FormData` entries in Server Actions which regressed in 19.0.6 (@unstubbable [#36568](https://github.com/facebook/react/pull/36568))

## 19.0.6 (May 6, 2026)

### React Server Components

- Type hardening and performance improvements (@eps1lon, @unstubbable [#36425](https://github.com/facebook/react/pull/36425))

## 19.0.5 (March 18, 2026)

### React Server Components

- Add more cycle protections (@eps1lon, @unstubbable [#36236](https://github.com/facebook/react/pull/36236))

## 19.0.4 (Jan 26, 2026)

### React Server Components

- Add more DoS mitigations to Server Actions, and harden Server Components (@gnoff, @lubieowoce, @sebmarkbage, @unstubbable [#35632](https://github.com/facebook/react/pull/35632))

## 19.0.3 (Dec 11, 2025)

### React Server Components

- Add extra loop protection to React Server Functions (@sebmarkbage [#35351](https://github.com/facebook/react/pull/35351))

## 19.0.2 (Dec 11, 2025)

### React Server Components

- Patch Promise cycles and toString on Server Functions (@sebmarkbage, @unstubbable [#35289](https://github.com/facebook/react/pull/35289), [#35345](https://github.com/facebook/react/pull/35345))

## 19.0.1 (Dec 3, 2025)

### React Server Components

- Bring React Server Component fixes to Server Actions (@sebmarkbage [#35277](https://github.com/facebook/react/pull/35277))

## 19.0.0 (December 5, 2024)

Below is a list of all new features, APIs, deprecations, and breaking changes. Read [React 19 release post](https://react.dev/blog/2024/04/25/react-19) and [React 19 upgrade guide](https://react.dev/blog/2024/04/25/react-19-upgrade-guide) for more information.

> 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](https://19.react.dev/reference/rsc/server-components) 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](https://testing-library.com/docs/react-testing-library/intro/) or [@testing-library/react-native](https://testing-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](https://19.react.dev/blog/2024/04/25/react-19-upgrade-guide) for more details and guidance on codemodding.

### React

* New JSX Transform is now required: We introduced [a new JSX transform](https://legacy.reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) 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-test-renderer/shallow`: This has been a re-export of [react-shallow-renderer](https://github.com/enzymejs/react-shallow-renderer) since React 18\. If needed, you can continue to use the third-party package directly. We recommend using [@testing-library/react](https://testing-library.com/docs/react-testing-library/intro/) or [@testing-library/react-native](https://testing-library.com/docs/react-native-testing-library/intro) instead.

#### React DOM

* 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.  
* Support for Custom Elements: React 19 now passes all tests on [Custom Elements Everywhere](https://custom-elements-everywhere.com/).  
* 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](http://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: `number | string`)  
  * `VoidFunctionComponent` (replacement: `FunctionComponent`)  
  * `VFC` (replacement: `FC`)  
  * 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,  
  ```diff
  -useReducer<React.Reducer<State, Action>>(reducer)
  +useReducer(reducer)
  ```
  or
  ```diff
  -useReducer<React.Reducer<State, Action>>(reducer)
  +useReducer<State, Action>(reducer)
  ```

### All Changes

#### React

* Add support for async Actions ([\#26621](https://github.com/facebook/react/pull/26621), [\#26726](https://github.com/facebook/react/pull/26726), [\#28078](https://github.com/facebook/react/pull/28078), [\#28097](https://github.com/facebook/react/pull/28097), [\#29226](https://github.com/facebook/react/pull/29226), [\#29618](https://github.com/facebook/react/pull/29618), [\#29670](https://github.com/facebook/react/pull/29670), [\#26716](https://github.com/facebook/react/pull/26716) by [@acdlite](https://github.com/acdlite) and [@sebmarkbage](https://github.com/sebmarkbage))  
* Add `useActionState()` hook to update state based on the result of a Form Action ([\#27270](https://github.com/facebook/react/pull/27270), [\#27278](https://github.com/facebook/react/pull/27278), [\#27309](https://github.com/facebook/react/pull/27309), [\#27302](https://github.com/facebook/react/pull/27302), [\#27307](https://github.com/facebook/react/pull/27307), [\#27366](https://github.com/facebook/react/pull/27366), [\#27370](https://github.com/facebook/react/pull/27370), [\#27321](https://github.com/facebook/react/pull/27321), [\#27374](https://github.com/facebook/react/pull/27374), [\#27372](https://github.com/facebook/react/pull/27372), [\#27397](https://github.com/facebook/react/pull/27397), [\#27399](https://github.com/facebook/react/pull/27399), [\#27460](https://github.com/facebook/react/pull/27460), [\#28557](https://github.com/facebook/react/pull/28557), [\#27570](https://github.com/facebook/react/pull/27570), [\#27571](https://github.com/facebook/react/pull/27571), [\#28631](https://github.com/facebook/react/pull/28631), [\#28788](https://github.com/facebook/react/pull/28788), [\#29694](https://github.com/facebook/react/pull/29694), [\#29695](https://github.com/facebook/react/pull/29695), [\#29694](https://github.com/facebook/react/pull/29694), [\#29665](https://github.com/facebook/react/pull/29665), [\#28232](https://github.com/facebook/react/pull/28232), [\#28319](https://github.com/facebook/react/pull/28319) by [@acdlite](https://github.com/acdlite), [@eps1lon](https://github.com/eps1lon), and [@rickhanlonii](https://github.com/rickhanlonii))  
* Add `use()` API to read resources in render ([\#25084](https://github.com/facebook/react/pull/25084), [\#25202](https://github.com/facebook/react/pull/25202), [\#25207](https://github.com/facebook/react/pull/25207), [\#25214](https://github.com/facebook/react/pull/25214), [\#25226](https://github.com/facebook/react/pull/25226), [\#25247](https://github.com/facebook/react/pull/25247), [\#25539](https://github.com/facebook/react/pull/25539), [\#25538](https://github.com/facebook/react/pull/25538), [\#25537](https://github.com/facebook/react/pull/25537), [\#25543](https://github.com/facebook/react/pull/25543), [\#25561](https://github.com/facebook/react/pull/25561), [\#25620](https://github.com/facebook/react/pull/25620), [\#25615](https://github.com/facebook/react/pull/25615), [\#25922](https://github.com/facebook/react/pull/25922), [\#25641](https://github.com/facebook/react/pull/25641), [\#25634](https://github.com/facebook/react/pull/25634), [\#26232](https://github.com/facebook/react/pull/26232), [\#26536](https://github.com/facebook/react/pull/26535), [\#26739](https://github.com/facebook/react/pull/26739), [\#28233](https://github.com/facebook/react/pull/28233) by [@acdlite](https://github.com/acdlite), [@MofeiZ](https://github.com/mofeiZ), [@sebmarkbage](https://github.com/sebmarkbage), [@sophiebits](https://github.com/sophiebits), [@eps1lon](https://github.com/eps1lon), and [@hansottowirtz](https://github.com/hansottowirtz))  
* Add `useOptimistic()` hook to display mutated state optimistically during an async mutation ([\#26740](https://github.com/facebook/react/pull/26740), [\#26772](https://github.com/facebook/react/pull/26772), [\#27277](https://github.com/facebook/react/pull/27277), [\#27453](https://github.com/facebook/react/pull/27453), [\#27454](https://github.com/facebook/react/pull/27454), [\#27936](https://github.com/facebook/react/pull/27936) by [@acdlite](https://github.com/acdlite))  
* Added an `initialValue` argument to `useDeferredValue()` hook ([\#27500](https://github.com/facebook/react/pull/27500), [\#27509](https://github.com/facebook/react/pull/27509), [\#27512](https://github.com/facebook/react/pull/27512), [\#27888](https://github.com/facebook/react/pull/27888), [\#27550](https://github.com/facebook/react/pull/27550) by [@acdlite](https://github.com/acdlite))  
* Support refs as props, warn on `element.ref` access ([\#28348](https://github.com/facebook/react/pull/28348), [\#28464](https://github.com/facebook/react/pull/28464), [\#28731](https://github.com/facebook/react/pull/28731) by [@acdlite](https://github.com/acdlite))  
* Support Custom Elements ([\#22184](https://github.com/facebook/react/pull/22184), [\#26524](https://github.com/facebook/react/pull/26524), [\#26523](https://github.com/facebook/react/pull/26523), [\#27511](https://github.com/facebook/react/pull/27511), [\#24541](https://github.com/facebook/react/pull/24541) by [@josepharhar](https://github.com/josepharhar), [@sebmarkbage](https://github.com/sebmarkbage), [@gnoff](https://github.com/gnoff) and [@eps1lon](https://github.com/eps1lon))  
* Add ref cleanup function ([\#25686](https://github.com/facebook/react/pull/25686), [\#28883](https://github.com/facebook/react/pull/28883), [\#28910](https://github.com/facebook/react/pull/28910)  by [@sammy-SC](https://github.com/sammy-SC), [@jackpope](https://github.com/jackpope), and [@kassens](https://github.com/kassens))  
* Sibling pre-rendering replaced by sibling pre-warming ([\#26380](https://github.com/facebook/react/pull/26380), [\#26549](https://github.com/facebook/react/pull/26549), [\#30761](https://github.com/facebook/react/pull/30761), [\#30800](https://github.com/facebook/react/pull/30800), [\#30762](https://github.com/facebook/react/pull/30762), [\#30879](https://github.com/facebook/react/pull/30879), [\#30934](https://github.com/facebook/react/pull/30934), [\#30952](https://github.com/facebook/react/pull/30952), [\#31056](https://github.com/facebook/react/pull/31056), [\#31452](https://github.com/facebook/react/pull/31452) by [@sammy-SC](https://github.com/sammy-SC), [@acdlite](https://github.com/acdlite), [@gnoff](https://github.com/gnoff), [@jackpope](https://github.com/jackpope), [@rickhanlonii](https://github.com/rickhanlonii))  
* Don’t rethrow errors at the root ([\#28627](https://github.com/facebook/react/pull/28627), [\#28641](https://github.com/facebook/react/pull/28641) by [@sebmarkbage](https://github.com/sebmarkbage))  
* Batch sync discrete, continuous, and default lanes ([\#25700](https://github.com/facebook/react/pull/25700) by [@tyao1](https://github.com/tyao1))  
* Switch `<Context>` to mean `<Context.Provider>` ([\#28226](https://github.com/facebook/react/pull/28226) by [@gaearon](https://github.com/gaearon))  
* Changes to *StrictMode*  
  * Handle `info`, `group`, and `groupCollapsed` in *StrictMode* logging ([\#25172](https://github.com/facebook/react/pull/25172) by [@timneutkens](https://github.com/timneutkens))  
  * Refs are now attached/detached/attached in *StrictMode* ([\#25049](https://github.com/facebook/react/pull/25049) by [@sammy-SC](https://github.com/sammy-SC))  
  * Fix `useSyncExternalStore()` hydration in *StrictMode* ([\#26791](https://github.com/facebook/react/pull/26791) by [@sophiebits](https://github.com/sophiebits))  
  * Always trigger `componentWillUnmount()` in *StrictMode* ([\#26842](https://github.com/facebook/react/pull/26842) by [@tyao1](https://github.com/tyao1))  
  * Restore double invoking `useState()` and `useReducer()` initializer functions in *StrictMode* ([\#28248](https://github.com/facebook/react/pull/28248) by [@eps1lon](https://github.com/eps1lon))  
  * Reuse memoized result from first pass ([\#25583](https://github.com/facebook/react/pull/25583) by [@acdlite](https://github.com/acdlite))  
  * Fix `useId()` in *StrictMode* ([\#25713](https://github.com/facebook/react/pull/25713) by [@gnoff](https://github.com/gnoff))  
  * Add component name to *StrictMode* error messages ([\#25718](https://github.com/facebook/react/pull/25718) by [@sammy-SC](https://github.com/sammy-SC))  
* Add support for rendering BigInt ([\#24580](https://github.com/facebook/react/pull/24580) by [@eps1lon](https://github.com/eps1lon))  
* `act()` no longer checks `shouldYield` which can be inaccurate in test environments ([\#26317](https://github.com/facebook/react/pull/26317) by [@acdlite](https://github.com/acdlite))  
* Warn when keys are spread with props ([\#25697](https://github.com/facebook/react/pull/25697), [\#26080](https://github.com/facebook/react/pull/26080) by [@sebmarkbage](https://github.com/sebmarkbage) and [@kassens](https://github.com/kassens))  
* Generate sourcemaps for production build artifacts ([\#26446](https://github.com/facebook/react/pull/26446) by [@markerikson](https://github.com/markerikson))  
* Improve stack diffing algorithm ([\#27132](https://github.com/facebook/react/pull/27132) by [@KarimP](https://github.com/KarimP))  
* Suspense throttling lowered from 500ms to 300ms ([\#26803](https://github.com/facebook/react/pull/26803) by [@acdlite](https://github.com/acdlite))  
* Lazily propagate context changes ([\#20890](https://github.com/facebook/react/pull/20890) by [@acdlite](https://github.com/acdlite) and [@gnoff](https://github.com/gnoff))  
* Immediately rerender pinged fiber ([\#25074](https://github.com/facebook/react/pull/25074) by [@acdlite](https://github.com/acdlite))  
* Move update scheduling to microtask ([\#26512](https://github.com/facebook/react/pull/26512) by [@acdlite](https://github.com/acdlite))  
* Consistently apply throttled retries ([\#26611](https://github.com/facebook/react/pull/26611), [\#26802](https://github.com/facebook/react/pull/26802) by [@acdlite](https://github.com/acdlite))  
* Suspend Thenable/Lazy if it's used in React.Children ([\#28284](https://github.com/facebook/react/pull/28284) by [@sebmarkbage](https://github.com/sebmarkbage))  
* Detect infinite update loops caused by render phase updates ([\#26625](https://github.com/facebook/react/pull/26625) by [@acdlite](https://github.com/acdlite))  
* Update conditional hooks warning ([\#29626](https://github.com/facebook/react/pull/29626) by [@sophiebits](https://github.com/sophiebits))  
* Update error URLs to go to new docs ([\#27240](https://github.com/facebook/react/pull/27240) by [@rickhanlonii](https://github.com/rickhanlonii))  
* Rename the `react.element` symbol to `react.transitional.element` ([\#28813](https://github.com/facebook/react/pull/28813) by [@sebmarkbage](https://github.com/sebmarkbage))  
* Fix crash when suspending in shell during `useSyncExternalStore()` re-render ([\#27199](https://github.com/facebook/react/pull/27199) by [@acdlite](https://github.com/acdlite))  
* Fix incorrect “detected multiple renderers" error in tests ([\#22797](https://github.com/facebook/react/pull/22797) by [@eps1lon](https://github.com/eps1lon))  
* Fix bug where effect cleanup may be called twice after bailout ([\#26561](https://github.com/facebook/react/pull/26561) by [@acdlite](https://github.com/acdlite))  
* Fix suspending in shell during discrete update ([\#25495](https://github.com/facebook/react/pull/25495) by [@acdlite](https://github.com/acdlite))  
* Fix memory leak after repeated setState bailouts ([\#25309](https://github.com/facebook/react/pull/25309) by [@acdlite](https://github.com/acdlite))  
* Fix `useSyncExternalStore()` dropped update when state is dispatched in render phase ([\#25578](https://github.com/facebook/react/pull/25578) by [@pandaiolo](https://github.com/pandaiolo))  
* Fix logging when rendering a lazy fragment ([\#30372](https://github.com/facebook/react/pull/30372) by [@tom-sherman](https://github.com/tom-sherman))  
* Remove string refs ([\#25383](https://github.com/facebook/react/pull/25383), [\#28322](https://github.com/facebook/react/pull/28322) by [@eps1lon](https://github.com/eps1lon) and [@acdlite](https://github.com/acdlite))  
* Remove Legacy Context (\#30319 by [@kassens](https://github.com/kassens))  
* Remove `RefreshRuntime.findAffectedHostInstances` ([\#30538](https://github.com/facebook/react/pull/30538) by [@gaearon](https://github.com/gaearon))  
* Remove client caching from `cache()` API ([\#27977](https://github.com/facebook/react/pull/27977), [\#28250](https://github.com/facebook/react/pull/28250) by [@acdlite](https://github.com/acdlite) and [@gnoff](https://github.com/gnoff))  
* Remove `propTypes` ([\#28324](https://github.com/facebook/react/pull/28324), [\#28326](https://github.com/facebook/react/pull/28326) by [@gaearon](https://github.com/gaearon))  
* Remove `defaultProps` support, except for classes ([\#28733](https://github.com/facebook/react/pull/28733) by [@acdlite](https://github.com/acdlite))  
* Remove UMD builds ([\#28735](https://github.com/facebook/react/pull/28735) by [@gnoff](https://github.com/gnoff))  
* Remove delay for non-transition updates ([\#26597](https://github.com/facebook/react/pull/26597) by [@acdlite](https://github.com/acdlite))  
* Remove `createFactory` ([\#27798](https://github.com/facebook/react/pull/27798) by [@kassens](https://github.com/kassens))

#### React DOM

* Adds Form Actions to handle form submission ([\#26379](https://github.com/facebook/react/pull/26379), [\#26674](https://github.com/facebook/react/pull/26674), [\#26689](https://github.com/facebook/react/pull/26689), [\#26708](https://github.com/facebook/react/pull/26708), [\#26714](https://github.com/facebook/react/pull/26714),  [\#26735](https://github.com/facebook/react/pull/26735), [\#26846](https://github.com/facebook/react/pull/26846), [\#27358](https://github.com/facebook/react/pull/27358),  [\#28056](https://github.com/facebook/react/pull/28056) by [@sebmarkbage](https://github.com/sebmarkbage), [@acdlite](https://github.com/acdlite), and [@jupapios](https://github.com/jupapios))  
* Add `useFormStatus()` hook to provide status information of the last form submission ([\#26719](https://github.com/facebook/react/pull/26719), [\#26722](https://github.com/facebook/react/pull/26722), [\#26788](https://github.com/facebook/react/pull/26788),  [\#29019](https://github.com/facebook/react/pull/29019), [\#28728](https://github.com/facebook/react/pull/28728), [\#28413](https://github.com/facebook/react/pull/28413) by [@acdlite](https://github.com/acdlite) and [@eps1lon](https://github.com/eps1lon))  
* Support for Document Metadata. Adds `preinit`, `preinitModule`, `preconnect`, `prefetchDNS`, `preload`, and `preloadModule` APIs.  
  * [\#25060](https://github.com/facebook/react/pull/25060), [\#25243](https://github.com/facebook/react/pull/25243), [\#25388](https://github.com/facebook/react/pull/25388), [\#25432](https://github.com/facebook/react/pull/25432), [\#25436](https://github.com/facebook/react/pull/25436), [\#25426](https://github.com/facebook/react/pull/25426), [\#25500](https://github.com/facebook/react/pull/25500), [\#25480](https://github.com/facebook/react/pull/25480), [\#25508](https://github.com/facebook/react/pull/25508), [\#25515](https://github.com/facebook/react/pull/25515), [\#25514](https://github.com/facebook/react/pull/25514), [\#25532](https://github.com/facebook/react/pull/25532), [\#25536](https://github.com/facebook/react/pull/25536), [\#25534](https://github.com/facebook/react/pull/25534), [\#25546](https://github.com/facebook/react/pull/25546), [\#25559](https://github.com/facebook/react/pull/25559), [\#25569](https://github.com/facebook/react/pull/25569), [\#25599](https://github.com/facebook/react/pull/25599), [\#25689](https://github.com/facebook/react/pull/25689), [\#26106](https://github.com/facebook/react/pull/26106), [\#26152](https://github.com/facebook/react/pull/26152), [\#26239](https://github.com/facebook/react/pull/26239), [\#26237](https://github.com/facebook/react/pull/26237), [\#26280](https://github.com/facebook/react/pull/26280), [\#26154](https://github.com/facebook/react/pull/26154), [\#26256](https://github.com/facebook/react/pull/26256), [\#26353](https://github.com/facebook/react/pull/26353), [\#26427](https://github.com/facebook/react/pull/26427), [\#26450](https://github.com/facebook/react/pull/26450), [\#26502](https://github.com/facebook/react/pull/26502),  [\#26514](https://github.com/facebook/react/pull/26514), [\#26531](https://github.com/facebook/react/pull/26531), [\#26532](https://github.com/facebook/react/pull/26532), [\#26557](https://github.com/facebook/react/pull/26557), [\#26871](https://github.com/facebook/react/pull/26871), [\#26881](https://github.com/facebook/react/pull/26881), [\#26877](https://github.com/facebook/react/pull/26877), [\#26873](https://github.com/facebook/react/pull/26873), [\#26880](https://github.com/facebook/react/pull/26880), [\#26942](https://github.com/facebook/react/pull/26942), [\#26938](https://github.com/facebook/react/pull/26938), [\#26940](https://github.com/facebook/react/pull/26940), [\#26939](https://github.com/facebook/react/pull/26939), [\#27030](https://github.com/facebook/react/pull/27030), [\#27201](https://github.com/facebook/react/pull/27201), [\#27212](https://github.com/facebook/react/pull/27212), [\#27217](https://github.com/facebook/react/pull/27217), [\#27218](https://github.com/facebook/react/pull/27218), [\#27220](https://github.com/facebook/react/pull/27220), [\#27224](https://github.com/facebook/react/pull/27224), [\#27223](https://github.com/facebook/react/pull/27223), [\#27269](https://github.com/facebook/react/pull/27269), [\#27260](https://github.com/facebook/react/pull/27260), [\#27347](https://github.com/facebook/react/pull/27347), [\#27346](https://github.com/facebook/react/pull/27346), [\#27361](https://github.com/facebook/react/pull/27361), [\#27400](https://github.com/facebook/react/pull/27400), [\#27541](https://github.com/facebook/react/pull/27541), [\#27610](https://github.com/facebook/react/pull/27610), [\#28110](https://github.com/facebook/react/pull/28110), [\#29693](https://github.com/facebook/react/pull/29693), [\#29732](https://github.com/facebook/react/pull/29732), [\#29811](https://github.com/facebook/react/pull/29811), [\#27586](https://github.com/facebook/react/pull/27586), [\#28069](https://github.com/facebook/react/pull/28069) by [@gnoff](https://github.com/gnoff), [@sebmarkbage](https://github.com/sebmarkbage), [@acdlite](https://github.com/acdlite), [@kassens](https://github.com/kassens), [@sokra](https://github.com/sokra), [@sweetliquid](https://github.com/sweetliquid)  
* Add `fetchPriority` to `<img>` and `<link>` ([\#25927](https://github.com/facebook/react/pull/25927) by [@styfle](https://github.com/styfle))  
* Add support for SVG `transformOrigin` prop ([\#26130](https://github.com/facebook/react/pull/26130) by [@arav-ind](https://github.com/arav-ind))  
* Add support for `onScrollEnd` event ([\#26789](https://github.com/facebook/react/pull/26789) by [@devongovett](https://github.com/devongovett))  
* Allow `<hr>` as child of `<select>` ([\#27632](https://github.com/facebook/react/pull/27632) by [@SouSingh](https://github.com/SouSingh))  
* Add support for Popover API ([\#27981](https://github.com/facebook/react/pull/27981) by [@eps1lon](https://github.com/eps1lon))  
* Add support for `inert` ([\#24730](https://github.com/facebook/react/pull/24730) by [@eps1lon](https://github.com/eps1lon))  
* Add support for `imageSizes` and `imageSrcSet` ([\#22550](https://github.com/facebook/react/pull/22550) by [@eps1lon](https://github.com/eps1lon))  
* Synchronously flush transitions in popstate events ([\#26025](https://github.com/facebook/react/pull/26025), [\#27559](https://github.com/facebook/react/pull/27559), [\#27505](https://github.com/facebook/react/pull/27505), [\#30759](https://github.com/facebook/react/pull/30759) by [@tyao1](https://github.com/tyao1) and [@acdlite](https://github.com/acdlite))  
* `flushSync` exhausts queue even if something throws ([\#26366](https://github.com/facebook/react/pull/26366) by [@acdlite](https://github.com/acdlite))  
* Throw error if `react` and `react-dom` versions don’t match ([\#29236](https://github.com/facebook/react/pull/29236) by [@acdlite](https://github.com/acdlite))  
* Ensure `srcset` and `src` are assigned last on `<img>` instances ([\#30340](https://github.com/facebook/react/pull/30340) by [@gnoff](https://github.com/gnoff))  
* Javascript URLs are replaced with functions that throw errors ([\#26507](https://github.com/facebook/react/pull/26507), [\#29808](https://github.com/facebook/react/pull/29808) by [@sebmarkbage](https://github.com/sebmarkbage) and [@kassens](https://github.com/kassens))  
* Treat toggle and beforetoggle as discrete events ([\#29176](https://github.com/facebook/react/pull/29176) by [@eps1lon](https://github.com/eps1lon))  
* Filter out empty `src` and `href` attributes (unless for `<a href=”” />`) ([\#18513](https://github.com/facebook/react/pull/18513), [\#28124](https://github.com/facebook/react/pull/28124) by [@bvaughn](https://github.com/bvaughn) and [@eps1lon](https://github.com/eps1lon))  
* Fix unitless `scale` style property ([\#25601](https://github.com/facebook/react/pull/25601) by [@JonnyBurger](https://github.com/JonnyBurger))  
* Fix `onChange` error message for controlled `<select>` ([\#27740](https://github.com/facebook/react/pull/27740) by [@Biki-das](https://github.com/Biki-das))  
* Fix focus restore in child windows after element reorder ([\#30951](https://github.com/facebook/react/pull/30951) by [@ling1726](https://github.com/ling1726))  
* Remove `render`, `hydrate`, `findDOMNode`, `unmountComponentAtNode`, `unstable_createEventHandle`, `unstable_renderSubtreeIntoContainer`, and `unstable_runWithPriority`. Move `createRoot` and `hydrateRoot` to `react-dom/client`. ([\#28271](https://github.com/facebook/react/pull/28271) by [@gnoff](https://github.com/gnoff))  
* Remove `test-utils` ([\#28541](https://github.com/facebook/react/pull/28541) by [@eps1lon](https://github.com/eps1lon))  
* Remove `unstable_flushControlled` ([\#26397](https://github.com/facebook/react/pull/26397) by [@kassens](https://github.com/kassens))  
* Remove legacy mode ([\#28468](https://github.com/facebook/react/pull/28468) by [@gnoff](https://github.com/gnoff))  
* Remove `renderToStaticNodeStream()` ([\#28873](https://github.com/facebook/react/pull/28873) by @gnoff)  
* Remove `unstable_renderSubtreeIntoContainer` ([\#29771](https://github.com/facebook/react/pull/29771) by [@kassens](https://github.com/kassens))

#### React DOM Server

* Stable release of React Server Components ([Many, many PRs](https://github.com/facebook/react/pulls?q=is%3Apr+is%3Aclosed+%5BFlight%5D+in%3Atitle+created%3A%3C2024-12-01+) by [@sebmarkbage](https://github.com/sebmarkbage), [@acdlite](https://github.com/acdlite), [@gnoff](https://github.com/gnoff), [@sammy-SC](https://github.com/sammy-SC), [@gaearon](https://github.com/gaearon), [@sophiebits](https://github.com/sophiebits), [@unstubbable](https://github.com/unstubbable), [@lubieowoce](https://github.com/lubieowoce))
* Support Server Actions ([\#26124](https://github.com/facebook/react/pull/26124), [\#26632](https://github.com/facebook/react/pull/26632), [\#27459](https://github.com/facebook/react/pull/27459) by [@sebmarkbage](https://github.com/sebmarkbage) and [@acdlite](https://github.com/acdlite))  
* Changes to SSR  
  * Add external runtime which bootstraps hydration on the client for binary transparency ([\#25437](https://github.com/facebook/react/pull/25437), [\#26169](https://github.com/facebook/react/pull/26169), [\#25499](https://github.com/facebook/react/pull/25499) by [@MofeiZ](https://github.com/mofeiZ) and [@acdlite](https://github.com/acdlite))  
  * Support subresource integrity for `bootstrapScripts` and `bootstrapModules` ([\#25104](https://github.com/facebook/react/pull/25104) by [@gnoff](https://github.com/gnoff))  
  * Fix null bytes written at text chunk boundaries ([\#26228](https://github.com/facebook/react/pull/26228) by [@sophiebits](https://github.com/sophiebits))  
  * Fix logic around attribute serialization ([\#26526](https://github.com/facebook/react/pull/26526) by [@gnoff](https://github.com/gnoff))  
  * Fix precomputed chunk cleared on Node 18 ([\#25645](https://github.com/facebook/react/pull/25645) by [@feedthejim](https://github.com/feedthejim))  
  * Optimize end tag chunks ([\#27522](https://github.com/facebook/react/pull/27522) by [@yujunjung](https://github.com/yujunjung))  
  * Gracefully handle suspending in DOM configs ([\#26768](https://github.com/facebook/react/pull/26768) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Check for nullish values on ReactCustomFormAction ([\#26770](https://github.com/facebook/react/pull/26770) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Preload `bootstrapModules`, `bootstrapScripts`, and update priority queue ([\#26754](https://github.com/facebook/react/pull/26754), [\#26753](https://github.com/facebook/react/pull/26753), [\#27190](https://github.com/facebook/react/pull/27190), [\#27189](https://github.com/facebook/react/pull/27189) by [@gnoff](https://github.com/gnoff))  
  * Client render the nearest child or parent suspense boundary if replay errors or is aborted ([\#27386](https://github.com/facebook/react/pull/27386) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Don't bail out of flushing if we still have pending root tasks ([\#27385](https://github.com/facebook/react/pull/27385) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Ensure Resumable State is Serializable ([\#27388](https://github.com/facebook/react/pull/27388) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Remove extra render pass when reverting to client render ([\#26445](https://github.com/facebook/react/pull/26445) by [@acdlite](https://github.com/acdlite))  
  * Fix unwinding context during selective hydration ([\#25876](https://github.com/facebook/react/pull/25876) by [@tyao1](https://github.com/tyao1))  
  * Stop flowing and then abort if a stream is cancelled ([\#27405](https://github.com/facebook/react/pull/27405) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Pass cancellation reason to abort ([\#27536](https://github.com/facebook/react/pull/27536) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Add `onHeaders` entrypoint option ([\#27641](https://github.com/facebook/react/pull/27641), [\#27712](https://github.com/facebook/react/pull/27712) by [@gnoff](https://github.com/gnoff))  
  * Escape `<style>` and `<script>` textContent to enable rendering inner content without dangerouslySetInnerHTML ([\#28870](https://github.com/facebook/react/pull/28870), [\#28871](https://github.com/facebook/react/pull/28871) by [@gnoff](https://github.com/gnoff))  
  * Fallback to client replaying actions for Blob serialization ([\#28987](https://github.com/facebook/react/pull/28987) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Render Suspense fallback if boundary contains new stylesheet during sync update ([\#28965](https://github.com/facebook/react/pull/28965) by [@gnoff](https://github.com/gnoff))  
  * Fix header length tracking (\#30327 by [@gnoff](https://github.com/gnoff))  
  * Use `srcset` to trigger load event on mount (\#30351 by [@gnoff](https://github.com/gnoff))  
  * Don't perform work when closing stream (\#30497 by [@gnoff](https://github.com/gnoff))  
  * Allow aborting during render (\#30488, [\#30730](https://github.com/facebook/react/pull/30730) by [@gnoff](https://github.com/gnoff))  
  * Start initial work immediately (\#31079 by [@gnoff](https://github.com/gnoff))  
  * A transition flowing into a dehydrated boundary no longer suspends when showing fallback ([\#27230](https://github.com/facebook/react/pull/27230) by [@acdlite](https://github.com/acdlite))  
  * Fix selective hydration triggers false update loop error ([\#27439](https://github.com/facebook/react/pull/27439) by [@acdlite](https://github.com/acdlite))  
  * Warn for Child Iterator of all types but allow Generator Components ([\#28853](https://github.com/facebook/react/pull/28853) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Include regular stack trace in serialized errors ([\#28684](https://github.com/facebook/react/pull/28684), [\#28738](https://github.com/facebook/react/pull/28738) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Aborting early no longer infinitely suspends ([\#24751](https://github.com/facebook/react/pull/24751) by [@sebmarkbage](https://github.com/sebmarkbage))  
  * Fix hydration warning suppression in text comparisons ([\#24784](https://github.com/facebook/react/pull/24784) by [@gnoff](https://github.com/gnoff))  
  * Changes to error handling in SSR
    * Add diffs to hydration warnings ([\#28502](https://github.com/facebook/react/pull/28502), [\#28512](https://github.com/facebook/react/pull/28512) by [@sebmarkbage](https://github.com/sebmarkbage))  
    * Make Error creation lazy ([\#24728](https://github.com/facebook/react/pull/24728) by [@sebmarkbage](https://github.com/sebmarkbage))  
    * Remove recoverable error when a sync update flows into a dehydrated boundary ([\#25692](https://github.com/facebook/react/pull/25692) by [@sebmarkbage](https://github.com/sebmarkbage))  
    * Don't "fix up" mismatched text content with suppressedHydrationWarning ([\#26391](https://github.com/facebook/react/pull/26391) by [@sebmarkbage](https://github.com/sebmarkbage))  
    * Fix component stacks in errors ([\#27456](https://github.com/facebook/react/pull/27456) by [@sebmarkbage](https://github.com/sebmarkbage))  
    * Add component stacks to `onError` ([\#27761](https://github.com/facebook/react/pull/27761), [\#27850](https://github.com/facebook/react/pull/27850) by [@gnoff](https://github.com/gnoff) and [@sebmarkbage](https://github.com/sebmarkbage))  
    * Throw hydration mismatch errors once ([\#28502](https://github.com/facebook/react/pull/28502) by [@sebmarkbage](https://github.com/sebmarkbage))  
* Add Bun streaming server renderer ([\#25597](https://github.com/facebook/react/pull/25597) by [@colinhacks](https://github.com/colinhacks))  
* Add nonce support to bootstrap scripts ([\#26738](https://github.com/facebook/react/pull/26738) by [@danieltott](https://github.com/danieltott))  
* Add `crossorigin` support to bootstrap scripts ([\#26844](https://github.com/facebook/react/pull/26844) by [@HenriqueLimas](https://github.com/HenriqueLimas))  
* Support `nonce` and `fetchpriority` in preload links ([\#26826](https://github.com/facebook/react/pull/26826) by [@liuyenwei](https://github.com/liuyenwei))  
* Add `referrerPolicy` to `ReactDOM.preload()` ([\#27096](https://github.com/facebook/react/pull/27096) by [@styfle](https://github.com/styfle))  
* Add server condition for `react/jsx-dev-runtime` ([\#28921](https://github.com/facebook/react/pull/28921) by [@himself65](https://github.com/himself65))   
* Export version ([\#29596](https://github.com/facebook/react/pull/29596) by [@unstubbable](https://github.com/unstubbable))  
* Rename the secret export of Client and Server internals ([\#28786](https://github.com/facebook/react/pull/28786), [\#28789](https://github.com/facebook/react/pull/28789) by [@sebmarkbage](https://github.com/sebmarkbage))  
* Remove layout effect warning on server ([\#26395](https://github.com/facebook/react/pull/26395) by [@rickhanlonii](https://github.com/rickhanlonii))  
* Remove `errorInfo.digest` from `onRecoverableError` ([\#28222](https://github.com/facebook/react/pull/28222) by [@gnoff](https://github.com/gnoff))

#### ReactTestRenderer

* Add deprecation error to `react-test-renderer` on web ([\#27903](https://github.com/facebook/react/pull/27903), [\#28904](https://github.com/facebook/react/pull/28904) by [@jackpope](https://github.com/jackpope) and [@acdlite](https://github.com/acdlite))  
* Render with ConcurrentRoot on web ([\#28498](https://github.com/facebook/react/pull/28498) by [@jackpope](https://github.com/jackpope))  
* Remove `react-test-renderer/shallow` export ([\#25475](https://github.com/facebook/react/pull/25475), [\#28497](https://github.com/facebook/react/pull/28497) by [@sebmarkbage](https://github.com/sebmarkbage) and [@jackpope](https://github.com/jackpope))

#### React Reconciler

* Enable suspending commits without blocking render ([\#26398](https://github.com/facebook/react/pull/26398), [\#26427](https://github.com/facebook/react/pull/26427) by [@acdlite](https://github.com/acdlite))  
* Remove `prepareUpdate` ([\#26583](https://github.com/facebook/react/pull/26583), [\#27409](http://github.com/facebook/react/pull/27409) by [@sebmarkbage](https://github.com/sebmarkbage) and [@sophiebits](https://github.com/sophiebits))

#### React-Is

* Enable tree shaking ([\#27701](https://github.com/facebook/react/pull/27701) by [@markerikson](https://github.com/markerikson))  
* Remove `isConcurrentMode` and `isAsyncMode` methods ([\#28224](https://github.com/facebook/react/pull/28224) by @gaearon)

#### useSyncExternalStore

* Remove React internals access ([\#29868](https://github.com/facebook/react/pull/29868) by [@phryneas](https://github.com/phryneas))  
* Fix stale selectors keeping previous store references ([\#25969](https://github.com/facebook/react/pull/25968) by [@jellevoost](https://github.com/jellevoost))

## 18.3.1 (April 26, 2024)

- Export `act` from `react` [f1338f](https://github.com/facebook/react/commit/f1338f8080abd1386454a10bbf93d67bfe37ce85)

## 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](https://react.dev/blog/2024/04/25/react-19-upgrade-guide) for more info.

### React

- Allow writing to `this.refs` to support string ref codemod [909071](https://github.com/facebook/react/commit/9090712fd3ca4e1099e1f92e67933c2cb4f32552)
- Warn for deprecated `findDOMNode` outside StrictMode [c3b283](https://github.com/facebook/react/commit/c3b283964108b0e8dbcf1f9eb2e7e67815e39dfb)
- Warn for deprecated `test-utils` methods [d4ea75](https://github.com/facebook/react/commit/d4ea75dc4258095593b6ac764289f42bddeb835c)
- Warn for deprecated Legacy Context outside StrictMode [415ee0](https://github.com/facebook/react/commit/415ee0e6ea0fe3e288e65868df2e3241143d5f7f)
- Warn for deprecated string refs outside StrictMode [#25383](https://github.com/facebook/react/pull/25383)
- Warn for deprecated `defaultProps` for function components [#25699](https://github.com/facebook/react/pull/25699)
- Warn when spreading `key` [#25697](https://github.com/facebook/react/pull/25697)
- Warn when using `act` from `test-utils` [d4ea75](https://github.com/facebook/react/commit/d4ea75dc4258095593b6ac764289f42bddeb835c)

### React DOM
- Warn for deprecated `unmountComponentAtNode` [8a015b](https://github.com/facebook/react/commit/8a015b68cc060079878e426610e64e86fb328f8d)
- Warn for deprecated `renderToStaticNodeStream` [#28874](https://github.com/facebook/react/pull/28874)

## 18.2.0 (June 14, 2022)

### React DOM

* Provide a component stack as a second argument to `onRecoverableError`. ([@gnoff](https://github.com/gnoff) in [#24591](https://github.com/facebook/react/pull/24591))
* Fix hydrating into `document` causing a blank page on mismatch. ([@gnoff](https://github.com/gnoff) in [#24523](https://github.com/facebook/react/pull/24523))
* Fix false positive hydration errors with Suspense. ([@gnoff](https://github.com/gnoff) in [#24480](https://github.com/facebook/react/pull/24480) and  [@acdlite](https://github.com/acdlite) in [#24532](https://github.com/facebook/react/pull/24532))
* Fix ignored `setState` in Safari when adding an iframe. ([@gaearon](https://github.com/gaearon) in [#24459](https://github.com/facebook/react/pull/24459))

### React DOM Server

* Pass information about server errors to the client. ([@salazarm](https://github.com/salazarm) and [@gnoff](https://github.com/gnoff) in [#24551](https://github.com/facebook/react/pull/24551) and [#24591](https://github.com/facebook/react/pull/24591))
* Allow to provide a reason when aborting the HTML stream. ([@gnoff](https://github.com/gnoff) in [#24680](https://github.com/facebook/react/pull/24680))
* Eliminate extraneous text separators in the HTML where possible. ([@gnoff](https://github.com/gnoff) in [#24630](https://github.com/facebook/react/pull/24630))
* Disallow complex children inside `<title>` elements to match the browser constraints. ([@gnoff](https://github.com/gnoff) in [#24679](https://github.com/facebook/react/pull/24679))
* Fix buffering in some worker environments by explicitly setting `highWaterMark` to `0`. ([@jplhomer](https://github.com/jplhomer) in [#24641](https://github.com/facebook/react/pull/24641))

### Server Components (Experimental)

* Add support for `useId()` inside Server Components. ([@gnoff](https://github.com/gnoff) in [#24172](https://github.com/facebook/react/pull/24172))

## 18.1.0 (April 26, 2022)

### React DOM

* Fix the false positive warning about `react-dom/client` when using UMD bundle. ([@alireza-molaee](https://github.com/alireza-molaee) in [#24274](https://github.com/facebook/react/pull/24274))
* Fix `suppressHydrationWarning` to work in production too. ([@gaearon](https://github.com/gaearon) in [#24271](https://github.com/facebook/react/pull/24271))
* Fix `componentWillUnmount` firing twice inside of Suspense. ([@acdlite](https://github.com/acdlite) in [#24308](https://github.com/facebook/react/pull/24308))
* Fix some transition updates being ignored. ([@acdlite](https://github.com/acdlite) in [#24353](https://github.com/facebook/react/pull/24353))
* Fix `useDeferredValue` causing an infinite loop when passed an unmemoized value. ([@acdlite](https://github.com/acdlite) in [#24247](https://github.com/facebook/react/pull/24247))
* Fix throttling of revealing Suspense fallbacks. ([@sunderls](https://github.com/sunderls) in [#24253](https://github.com/facebook/react/pull/24253))
* Fix an inconsistency in whether the props object is the same between renders. ([@Andarist](https://github.com/Andarist) and [@acdlite](https://github.com/acdlite) in [#24421](https://github.com/facebook/react/pull/24421))
* Fix a missing warning about a `setState` loop in `useEffect`. ([@gaearon](https://github.com/gaearon) in [#24298](https://github.com/facebook/react/pull/24298))
* Fix a spurious hydration error. ([@gnoff](https://github.com/gnoff) in [#24404](https://github.com/facebook/react/pull/24404))
* Warn when calling `setState` in `useInsertionEffect`. ([@gaearon](https://github.com/gaearon) in [#24295](https://github.com/facebook/react/pull/24295))
* Ensure the reason for hydration errors is always displayed. ([@gaearon](https://github.com/gaearon) in [#24276](https://github.com/facebook/react/pull/24276))

### React DOM Server

* Fix escaping for the `bootstrapScriptContent` contents. ([@gnoff](https://github.com/gnoff) in [#24385](https://github.com/facebook/react/pull/24385))
* Significantly improve performance of `renderToPipeableStream`. ([@gnoff](https://github.com/gnoff) in [#24291](https://github.com/facebook/react/pull/24291))

### ESLint Plugin: React Hooks

* Fix false positive errors with a large number of branches. ([@scyron6](https://github.com/scyron6) in [#24287](https://github.com/facebook/react/pull/24287))
* Don't consider a known dependency stable when the variable is reassigned. ([@afzalsayed96](https://github.com/afzalsayed96) in [#24343](https://github.com/facebook/react/pull/24343))

### Use Subscription

* Replace the implementation with the `use-sync-external-store` shim. ([@gaearon](https://github.com/gaearon) in [#24289](https://github.com/facebook/react/pull/24289))

## 18.0.0 (March 29, 2022)

Below is a list of all new features, APIs, deprecations, and breaking changes.
Read [React 18 release post](https://reactjs.org/blog/2022/03/29/react-v18.html) and [React 18 upgrade guide](https://reactjs.org/blog/2022/03/08/react-18-upgrade-guide.html) for more information.

### New Features

### React

* `useId` is 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 it’s even more important in React 18 because of how the new streaming server renderer delivers HTML out-of-order.
* `startTransition` and `useTransition` let 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).
* `useDeferredValue` lets 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.
* `useSyncExternalStore` is a new hook that allows external stores to support concurrent reads by forcing updates to the store to be synchronous. It removes the need for `useEffect` when implementing subscriptions to external data sources, and is recommended for any library that integrates with state external to React.
* `useInsertionEffect` is a new hook that allows CSS-in-JS libraries to address performance issues of injecting styles in render. Unless you’ve already built a CSS-in-JS library we don’t 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 to `render` or `unmount`. Use it instead of `ReactDOM.render`. New features in React 18 don't work without it.
* `hydrateRoot`: New method to hydrate a server rendered application. Use it instead of `ReactDOM.hydrate` in 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`](https://developer.mozilla.org/en-US/docs/Web/API/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.render` has been deprecated. Using it will warn and run your app in React 17 mode.
* `react-dom`: `ReactDOM.hydrate` has been deprecated. Using it will warn and run your app in React 17 mode.
* `react-dom`: `ReactDOM.unmountComponentAtNode` has been deprecated.
* `react-dom`: `ReactDOM.renderSubtreeIntoContainer` has been deprecated.
* `react-dom/server`: `ReactDOMServer.renderToNodeStream` has 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](https://github.com/reactwg/react-18/discussions/21) 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`, and `Object.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/tracing` API

## Notable Changes

### React

* **Components can now render `undefined`:** React no longer throws if you return `undefined` from 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 a `return` statement before JSX.
* **In tests, `act` warnings are now opt-in:** If you're running end-to-end tests, the `act` warnings are unnecessary. We've introduced an [opt-in](https://github.com/reactwg/react-18/discussions/102) mechanism so you can enable them only for unit tests where they are useful and beneficial.
* **No warning about `setState` on unmounted components:** Previously, React warned about memory leaks when you call `setState` on 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](https://github.com/facebook/react/pull/22114) 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](https://github.com/facebook/react/issues/21783) 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 like `renderToPipeableStream` or `renderToReadableStream` instead.
* **`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

* Add `useTransition` and `useDeferredValue` to separate urgent updates from transitions. ([#10426](https://github.com/facebook/react/pull/10426), [#10715](https://github.com/facebook/react/pull/10715), [#15593](https://github.com/facebook/react/pull/15593), [#15272](https://github.com/facebook/react/pull/15272), [#15578](https://github.com/facebook/react/pull/15578), [#15769](https://github.com/facebook/react/pull/15769), [#17058](https://github.com/facebook/react/pull/17058), [#18796](https://github.com/facebook/react/pull/18796), [#19121](https://github.com/facebook/react/pull/19121), [#19703](https://github.com/facebook/react/pull/19703), [#19719](https://github.com/facebook/react/pull/19719), [#19724](https://github.com/facebook/react/pull/19724), [#20672](https://github.com/facebook/react/pull/20672), [#20976](https://github.com/facebook/react/pull/20976) by [@acdlite](https://github.com/acdlite), [@lunaruan](https://github.com/lunaruan), [@rickhanlonii](https://github.com/rickhanlonii), and [@sebmarkbage](https://github.com/sebmarkbage))
* Add `useId` for generating unique IDs. ([#17322](https://github.com/facebook/react/pull/17322), [#18576](https://github.com/facebook/react/pull/18576), [#22644](https://github.com/facebook/react/pull/22644), [#22672](https://github.com/facebook/react/pull/22672), [#21260](https://github.com/facebook/react/pull/21260) by [@acdlite](https://github.com/acdlite), [@lunaruan](https://github.com/lunaruan), and [@sebmarkbage](https://github.com/sebmarkbage))
* Add `useSyncExternalStore` to help external store libraries integrate with React. ([#15022](https://github.com/facebook/react/pull/15022), [#18000](https://github.com/facebook/react/pull/18000), [#18771](https://github.com/facebook/react/pull/18771), [#22211](https://github.com/facebook/react/pull/22211), [#22292](https://github.com/facebook/react/pull/22292), [#22239](https://github.com/facebook/react/pull/22239), [#22347](https://github.com/facebook/react/pull/22347), [#23150](https://github.com/facebook/react/pull/23150) by [@acdlite](https://github.com/acdlite), [@bvaughn](https://github.com/bvaughn), and [@drarmstr](https://github.com/drarmstr))
* Add `startTransition` as a version of `useTransition` without pending feedback. ([#19696](https://github.com/facebook/react/pull/19696) by [@rickhanlonii](https://github.com/rickhanlonii))
* Add `useInsertionEffect` for CSS-in-JS libraries. ([#21913](https://github.com/facebook/react/pull/21913) by [@rickhanlonii](https://github.com/rickhanlonii))
* Make Suspense remount layout effects when content reappears. ([#19322](https://github.com/facebook/react/pull/19322), [#19374](https://github.com/facebook/react/pull/19374), [#19523](https://github.com/facebook/react/pull/19523), [#20625](https://github.com/facebook/react/pull/20625), [#21079](https://github.com/facebook/react/pull/21079) by [@acdlite](https://github.com/acdlite), [@bvaughn](https://github.com/bvaughn), and [@lunaruan](https://github.com/lunaruan))
* Make `<StrictMode>` re-run effects to check for restorable state. ([#19523](https://github.com/facebook/react/pull/19523) , [#21418](https://github.com/facebook/react/pull/21418) by [@bvaughn](https://github.com/bvaughn) and [@lunaruan](https://github.com/lunaruan))
* Assume Symbols are always available. ([#23348](https://github.com/facebook/react/pull/23348) by [@sebmarkbage](https://github.com/sebmarkbage))
* Remove `object-assign` polyfill. ([#23351](https://github.com/facebook/react/pull/23351) by [@sebmarkbage](https://github.com/sebmarkbage))
* Remove unsupported `unstable_changedBits` API. ([#20953](https://github.com/facebook/react/pull/20953) by [@acdlite](https://github.com/acdlite))
* Allow components to render undefined. ([#21869](https://github.com/facebook/react/pull/21869) by [@rickhanlonii](https://github.com/rickhanlonii))
* Flush `useEffect` resulting from discrete events like clicks synchronously. ([#21150](https://github.com/facebook/react/pull/21150) by [@acdlite](https://github.com/acdlite))
* Suspense `fallback={undefined}` now behaves the same as `null` and isn't ignored. ([#21854](https://github.com/facebook/react/pull/21854) by [@rickhanlonii](https://github.com/rickhanlonii))
* Consider all `lazy()` resolving to the same component equivalent. ([#20357](https://github.com/facebook/react/pull/20357) by [@sebmarkbage](https://github.com/sebmarkbage))
* Don't patch console during first render. ([#22308](https://github.com/facebook/react/pull/22308) by [@lunaruan](https://github.com/lunaruan))
* Improve memory usage. ([#21039](https://github.com/facebook/react/pull/21039) by [@bgirard](https://github.com/bgirard))
* Improve messages if string coercion throws (Temporal.*, Symbol, etc.) ([#22064](https://github.com/facebook/react/pull/22064) by [@justingrant](https://github.com/justingrant))
* Use `setImmediate` when available over `MessageChannel`. ([#20834](https://github.com/facebook/react/pull/20834) by [@gaearon](https://github.com/gaearon))
* Fix context failing to propagate inside suspended trees. ([#23095](https://github.com/facebook/react/pull/23095) by [@gaearon](https://github.com/gaearon))
* Fix `useReducer` observing incorrect props by removing the eager bailout mechanism. ([#22445](https://github.com/facebook/react/pull/22445) by [@josephsavona](https://github.com/josephsavona))
* Fix `setState` being ignored in Safari when appending iframes. ([#23111](https://github.com/facebook/react/pull/23111) by [@gaearon](https://github.com/gaearon))
* Fix a crash when rendering `ZonedDateTime` in the tree. ([#20617](https://github.com/facebook/react/pull/20617) by [@dimaqq](https://github.com/dimaqq))
* Fix a crash when document is set to `null` in tests. ([#22695](https://github.com/facebook/react/pull/22695) by [@SimenB](https://github.com/SimenB))
* Fix `onLoad` not triggering when concurrent features are on. ([#23316](https://github.com/facebook/react/pull/23316) by [@gnoff](https://github.com/gnoff))
* Fix a warning when a selector returns `NaN`.  ([#23333](https://github.com/facebook/react/pull/23333) by [@hachibeeDI](https://github.com/hachibeeDI))
* Fix the generated license header. ([#23004](https://github.com/facebook/react/pull/23004) by [@vitaliemiron](https://github.com/vitaliemiron))
* Add `package.json` as one of the entry points. ([#22954](https://github.com/facebook/react/pull/22954) by [@Jack](https://github.com/Jack-Works))
* Allow suspending outside a Suspense boundary. ([#23267](https://github.com/facebook/react/pull/23267) by [@acdlite](https://github.com/acdlite))
* Log a recoverable error whenever hydration fails. ([#23319](https://github.com/facebook/react/pull/23319) by [@acdlite](https://github.com/acdlite))

### React DOM

* Add `createRoot` and `hydrateRoot`. ([#10239](https://github.com/facebook/react/pull/10239), [#11225](https://github.com/facebook/react/pull/11225), [#12117](https://github.com/facebook/react/pull/12117), [#13732](https://github.com/facebook/react/pull/13732), [#15502](https://github.com/facebook/react/pull/15502), [#15532](https://github.com/facebook/react/pull/15532), [#17035](https://github.com/facebook/react/pull/17035), [#17165](https://github.com/facebook/react/pull/17165), [#20669](https://github.com/facebook/react/pull/20669), [#20748](https://github.com/facebook/react/pull/20748), [#20888](https://github.com/facebook/react/pull/20888), [#21072](https://github.com/facebook/react/pull/21072), [#21417](https://github.com/facebook/react/pull/21417), [#21652](https://github.com/facebook/react/pull/21652), [#21687](https://github.com/facebook/react/pull/21687), [#23207](https://github.com/facebook/react/pull/23207), [#23385](https://github.com/facebook/react/pull/23385) by [@acdlite](https://github.com/acdlite), [@bvaughn](https://github.com/bvaughn), [@gaearon](https://github.com/gaearon), [@lunaruan](https://github.com/lunaruan), [@rickhanlonii](https://github.com/rickhanlonii), [@trueadm](https://github.com/trueadm), and [@sebmarkbage](https://github.com/sebmarkbage))
* Add selective hydration. ([#14717](https://github.com/facebook/react/pull/14717), [#14884](https://github.com/facebook/react/pull/14884), [#16725](https://github.com/facebook/react/pull/16725), [#16880](https://github.com/facebook/react/pull/16880), [#17004](https://github.com/facebook/react/pull/17004), [#22416](https://github.com/facebook/react/pull/22416), [#22629](https://github.com/facebook/react/pull/22629), [#22448](https://github.com/facebook/react/pull/22448), [#22856](https://github.com/facebook/react/pull/22856), [#23176](https://github.com/facebook/react/pull/23176) by [@acdlite](https://github.com/acdlite), [@gaearon](https://github.com/gaearon), [@salazarm](https://github.com/salazarm), and [@sebmarkbage](https://github.com/sebmarkbage))
* Add `aria-description` to the list of known ARIA attributes. ([#22142](https://github.com/facebook/react/pull/22142) by [@mahyareb](https://github.com/mahyareb))
* Add `onResize` event to video elements. ([#21973](https://github.com/facebook/react/pull/21973) by [@rileyjshaw](https://github.com/rileyjshaw))
* Add `imageSizes` and `imageSrcSet` to known props. ([#22550](https://github.com/facebook/react/pull/22550) by [@eps1lon](https://github.com/eps1lon))
* Allow non-string `<option>` children if `value` is provided.  ([#21431](https://github.com/facebook/react/pull/21431) by [@sebmarkbage](https://github.com/sebmarkbage))
* Fix `aspectRatio` style not being applied. ([#21100](https://github.com/facebook/react/pull/21100) by [@gaearon](https://github.com/gaearon))
* Warn if `renderSubtreeIntoContainer` is called. ([#23355](https://github.com/facebook/react/pull/23355) by [@acdlite](https://github.com/acdlite))

### React DOM Server

* Add the new streaming renderer. ([#14144](https://github.com/facebook/react/pull/14144), [#20970](https://github.com/facebook/react/pull/20970), [#21056](https://github.com/facebook/react/pull/21056), [#21255](https://github.com/facebook/react/pull/21255), [#21200](https://github.com/facebook/react/pull/21200), [#21257](https://github.com/facebook/react/pull/21257), [#21276](https://github.com/facebook/react/pull/21276), [#22443](https://github.com/facebook/react/pull/22443), [#22450](https://github.com/facebook/react/pull/22450), [#23247](https://github.com/facebook/react/pull/23247), [#24025](https://github.com/facebook/react/pull/24025), [#24030](https://github.com/facebook/react/pull/24030) by [@sebmarkbage](https://github.com/sebmarkbage))
* Fix context providers in SSR when handling multiple requests. ([#23171](https://github.com/facebook/react/pull/23171) by [@frandiox](https://github.com/frandiox))
* Revert to client render on text mismatch. ([#23354](https://github.com/facebook/react/pull/23354) by [@acdlite](https://github.com/acdlite))
* Deprecate `renderToNodeStream`. ([#23359](https://github.com/facebook/react/pull/23359) by [@sebmarkbage](https://github.com/sebmarkbage))
* Fix a spurious error log in the new server renderer. ([#24043](https://github.com/facebook/react/pull/24043) by [@eps1lon](https://github.com/eps1lon))
* Fix a bug in the new server renderer. ([#22617](https://github.com/facebook/react/pull/22617) by [@shuding](https://github.com/shuding))
* Ignore function and symbol values inside custom elements on the server. ([#21157](https://github.com/facebook/react/pull/21157) by [@sebmarkbage](https://github.com/sebmarkbage))

### React DOM Test Utils

* Throw when `act` is used in production. ([#21686](https://github.com/facebook/react/pull/21686) by [@acdlite](https://github.com/acdlite))
* Support disabling spurious act warnings with `global.IS_REACT_ACT_ENVIRONMENT`. ([#22561](https://github.com/facebook/react/pull/22561) by [@acdlite](https://github.com/acdlite))
* Expand act warning to cover all APIs that might schedule React work. ([#22607](https://github.com/facebook/react/pull/22607) by [@acdlite](https://github.com/acdlite))
* Make `act` batch updates. ([#21797](https://github.com/facebook/react/pull/21797) by [@acdlite](https://github.com/acdlite))
* Remove warning for dangling passive effects. ([#22609](https://github.com/facebook/react/pull/22609) by [@acdlite](https://github.com/acdlite))

### React Refresh

* Track late-mounted roots in Fast Refresh. ([#22740](https://github.com/facebook/react/pull/22740) by [@anc95](https://github.com/anc95))
* Add `exports` field to `package.json`. ([#23087](https://github.com/facebook/react/pull/23087) by [@otakustay](https://github.com/otakustay))

### Server Components (Experimental)

* Add Server Context support. ([#23244](https://github.com/facebook/react/pull/23244) by [@salazarm](https://github.com/salazarm))
* Add `lazy` support. ([#24068](https://github.com/facebook/react/pull/24068) by [@gnoff](https://github.com/gnoff))
* Update webpack plugin for webpack 5 ([#22739](https://github.com/facebook/react/pull/22739) by [@michenly](https://github.com/michenly))
* Fix a mistake in the Node loader. ([#22537](https://github.com/facebook/react/pull/22537) by [@btea](https://github.com/btea))
* Use `globalThis` instead of `window` for edge environments. ([#22777](https://github.com/facebook/react/pull/22777) by [@huozhi](https://github.com/huozhi))

### Scheduler (Experimental)

* Remove unstable `scheduler/tracing` API ([#20037](https://github.com/facebook/react/pull/20037) by [@bvaughn](https://github.com/bvaughn))

## 17.0.2 (March 22, 2021)

### React DOM

* Remove an unused dependency to address the [`SharedArrayBuffer` cross-origin isolation warning](https://developer.chrome.com/blog/enabling-shared-array-buffer/). ([@koba04](https://github.com/koba04) and [@bvaughn](https://github.com/bvaughn) in [#20831](https://github.com/facebook/react/pull/20831), [#20832](https://github.com/facebook/react/pull/20832), and [#20840](https://github.com/facebook/react/pull/20840))

## 17.0.1 (October 22, 2020)

### React DOM

* Fix a crash in IE11. ([@gaearon](https://github.com/gaearon) in [#20071](https://github.com/facebook/react/pull/20071))

## 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.](https://reactjs.org/blog/2020/10/20/react-v17.html)**

### React

* Add `react/jsx-runtime` and `react/jsx-dev-runtime` for the [new JSX transform](https://babeljs.io/blog/2020/03/16/7.9.0#a-new-jsx-transform-11154-https-githubcom-babel-babel-pull-11154). ([@lunaruan](https://github.com/lunaruan) in [#18299](https://github.com/facebook/react/pull/18299))
* Build component stacks from native error frames. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18561](https://github.com/facebook/react/pull/18561))
* Allow to specify `displayName` on context for improved stacks. ([@eps1lon](https://github.com/eps1lon) in [#18224](https://github.com/facebook/react/pull/18224))
* Prevent `'use strict'` from leaking in the UMD bundles. ([@koba04](https://github.com/koba04) in [#19614](https://github.com/facebook/react/pull/19614))
* Stop using `fb.me` for redirects. ([@cylim](https://github.com/cylim) in [#19598](https://github.com/facebook/react/pull/19598))

### React DOM

* Delegate events to roots instead of `document`. ([@trueadm](https://github.com/trueadm) in [#18195](https://github.com/facebook/react/pull/18195) and [others](https://github.com/facebook/react/pulls?q=is%3Apr+author%3Atrueadm+modern+event+is%3Amerged))
* Clean up all effects before running any next effects. ([@bvaughn](https://github.com/bvaughn) in [#17947](https://github.com/facebook/react/pull/17947))
* Run `useEffect` cleanup functions asynchronously. ([@bvaughn](https://github.com/bvaughn) in [#17925](https://github.com/facebook/react/pull/17925))
* Use browser `focusin` and `focusout` for `onFocus` and `onBlur`. ([@trueadm](https://github.com/trueadm) in [#19186](https://github.com/facebook/react/pull/19186))
* Make all `Capture` events use the browser capture phase. ([@trueadm](https://github.com/trueadm) in [#19221](https://github.com/facebook/react/pull/19221))
* Don't emulate bubbling of the `onScroll` event. ([@gaearon](https://github.com/gaearon) in [#19464](https://github.com/facebook/react/pull/19464))
* Throw if `forwardRef` or `memo` component returns `undefined`. ([@gaearon](https://github.com/gaearon) in [#19550](https://github.com/facebook/react/pull/19550))
* Remove event pooling. ([@trueadm](https://github.com/trueadm) in [#18969](https://github.com/facebook/react/pull/18969))
* Stop exposing internals that won’t be needed by React Native Web. ([@necolas](https://github.com/necolas) in [#18483](https://github.com/facebook/react/pull/18483))
* Attach all known event listeners when the root mounts. ([@gaearon](https://github.com/gaearon) in [#19659](https://github.com/facebook/react/pull/19659))
* Disable `console` in the second render pass of DEV mode double render. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18547](https://github.com/facebook/react/pull/18547))
* Deprecate the undocumented and misleading `ReactTestUtils.SimulateNative` API. ([@gaearon](https://github.com/gaearon) in [#13407](https://github.com/facebook/react/pull/13407))
* Rename private field names used in the internals. ([@gaearon](https://github.com/gaearon) in [#18377](https://github.com/facebook/react/pull/18377))
* Don't call User Timing API in development. ([@gaearon](https://github.com/gaearon) in [#18417](https://github.com/facebook/react/pull/18417))
* Disable console during the repeated render in Strict Mode. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18547](https://github.com/facebook/react/pull/18547))
* In Strict Mode, double-render components without Hooks too. ([@eps1lon](https://github.com/eps1lon) in [#18430](https://github.com/facebook/react/pull/18430))
* Allow calling `ReactDOM.flushSync` during lifecycle methods (but warn). ([@sebmarkbage](https://github.com/sebmarkbage) in [#18759](https://github.com/facebook/react/pull/18759))
* Add the `code` property to the keyboard event objects. ([@bl00mber](https://github.com/bl00mber) in [#18287](https://github.com/facebook/react/pull/18287))
* Add the `disableRemotePlayback` property for `video` elements. ([@tombrowndev](https://github.com/tombrowndev) in [#18619](https://github.com/facebook/react/pull/18619))
* Add the `enterKeyHint` property for `input` elements. ([@eps1lon](https://github.com/eps1lon) in [#18634](https://github.com/facebook/react/pull/18634))
* Warn when no `value` is provided to `<Context.Provider>`. ([@charlie1404](https://github.com/charlie1404) in [#19054](https://github.com/facebook/react/pull/19054))
* Warn when `memo` or `forwardRef` components return `undefined`. ([@bvaughn](https://github.com/bvaughn) in [#19550](https://github.com/facebook/react/pull/19550))
* Improve the error message for invalid updates. ([@JoviDeCroock](https://github.com/JoviDeCroock) in [#18316](https://github.com/facebook/react/pull/18316))
* Exclude forwardRef and memo from stack frames. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18559](https://github.com/facebook/react/pull/18559))
* Improve the error message when switching between controlled and uncontrolled inputs. ([@vcarl](https://github.com/vcarl) in [#17070](https://github.com/facebook/react/pull/17070))
* Keep `onTouchStart`, `onTouchMove`, and `onWheel` passive. ([@gaearon](https://github.com/gaearon) in [#19654](https://github.com/facebook/react/pull/19654))
* Fix `setState` hanging in development inside a closed iframe. ([@gaearon](https://github.com/gaearon) in [#19220](https://github.com/facebook/react/pull/19220))
* Fix rendering bailout for lazy components with `defaultProps`. ([@jddxf](https://github.com/jddxf) in [#18539](https://github.com/facebook/react/pull/18539))
* Fix a false positive warning when `dangerouslySetInnerHTML` is `undefined`. ([@eps1lon](https://github.com/eps1lon) in [#18676](https://github.com/facebook/react/pull/18676))
* Fix Test Utils with non-standard `require` implementation. ([@just-boris](https://github.com/just-boris) in [#18632](https://github.com/facebook/react/pull/18632))
* Fix `onBeforeInput` reporting an incorrect `event.type`. ([@eps1lon](https://github.com/eps1lon) in [#19561](https://github.com/facebook/react/pull/19561))
* Fix `event.relatedTarget` reported as `undefined` in Firefox. ([@claytercek](https://github.com/claytercek) in [#19607](https://github.com/facebook/react/pull/19607))
* Fix "unspecified error" in IE11. ([@hemakshis](https://github.com/hemakshis) in [#19664](https://github.com/facebook/react/pull/19664))
* Fix rendering into a shadow root. ([@Jack-Works](https://github.com/Jack-Works) in [#15894](https://github.com/facebook/react/pull/15894))
* Fix `movementX/Y` polyfill with capture events. ([@gaearon](https://github.com/gaearon) in [#19672](https://github.com/facebook/react/pull/19672))
* Use delegation for `onSubmit` and `onReset` events. ([@gaearon](https://github.com/gaearon) in [#19333](https://github.com/facebook/react/pull/19333))
* Improve memory usage. ([@trueadm](https://github.com/trueadm) in [#18970](https://github.com/facebook/react/pull/18970))

### React DOM Server

* Make `useCallback` behavior consistent with `useMemo` for the server renderer. ([@alexmckenley](https://github.com/alexmckenley) in [#18783](https://github.com/facebook/react/pull/18783))
* Fix state leaking when a function component throws. ([@pmaccart](https://github.com/pmaccart) in [#19212](https://github.com/facebook/react/pull/19212))

### React Test Renderer

* Improve `findByType` error message. ([@henryqdineen](https://github.com/henryqdineen) in [#17439](https://github.com/facebook/react/pull/17439))

### Concurrent Mode (Experimental)

* Revamp the priority batching heuristics. ([@acdlite](https://github.com/acdlite) in [#18796](https://github.com/facebook/react/pull/18796))
* Add the `unstable_` prefix before the experimental APIs. ([@acdlite](https://github.com/acdlite) in [#18825](https://github.com/facebook/react/pull/18825))
* Remove `unstable_discreteUpdates` and `unstable_flushDiscreteUpdates`. ([@trueadm](https://github.com/trueadm) in [#18825](https://github.com/facebook/react/pull/18825))
* Remove the `timeoutMs` argument. ([@acdlite](https://github.com/acdlite) in [#19703](https://github.com/facebook/react/pull/19703))
* Disable `<div hidden />` prerendering in favor of a different future API. ([@acdlite](https://github.com/acdlite) in [#18917](https://github.com/facebook/react/pull/18917))
* Add `unstable_expectedLoadTime` to Suspense for CPU-bound trees. ([@acdlite](https://github.com/acdlite) in [#19936](https://github.com/facebook/react/pull/19936))
* Add an experimental `unstable_useOpaqueIdentifier` Hook. ([@lunaruan](https://github.com/lunaruan) in [#17322](https://github.com/facebook/react/pull/17322))
* Add an experimental `unstable_startTransition` API. ([@rickhanlonii](https://github.com/rickhanlonii) in [#19696](https://github.com/facebook/react/pull/19696))
* Using `act` in the test renderer no longer flushes Suspense fallbacks. ([@acdlite](https://github.com/acdlite) in [#18596](https://github.com/facebook/react/pull/18596))
* Use global render timeout for CPU Suspense. ([@sebmarkbage](https://github.com/sebmarkbage) in [#19643](https://github.com/facebook/react/pull/19643))
* Clear the existing root content before mounting. ([@bvaughn](https://github.com/bvaughn) in [#18730](https://github.com/facebook/react/pull/18730))
* Fix a bug with error boundaries. ([@acdlite](https://github.com/acdlite) in [#18265](https://github.com/facebook/react/pull/18265))
* Fix a bug causing dropped updates in a suspended tree. ([@acdlite](https://github.com/acdlite) in [#18384](https://github.com/facebook/react/pull/18384) and [#18457](https://github.com/facebook/react/pull/18457))
* Fix a bug causing dropped render phase updates. ([@acdlite](https://github.com/acdlite) in [#18537](https://github.com/facebook/react/pull/18537))
* Fix a bug in SuspenseList. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18412](https://github.com/facebook/react/pull/18412))
* Fix a bug causing Suspense fallback to show too early. ([@acdlite](https://github.com/acdlite) in [#18411](https://github.com/facebook/react/pull/18411))
* Fix a bug with class components inside SuspenseList. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18448](https://github.com/facebook/react/pull/18448))
* Fix a bug with inputs that may cause updates to be dropped. ([@jddxf](https://github.com/jddxf) in [#18515](https://github.com/facebook/react/pull/18515) and [@acdlite](https://github.com/acdlite) in [#18535](https://github.com/facebook/react/pull/18535))
* Fix a bug causing Suspense fallback to get stuck.  ([@acdlite](https://github.com/acdlite) in [#18663](https://github.com/facebook/react/pull/18663))
* Don't cut off the tail of a SuspenseList if hydrating. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18854](https://github.com/facebook/react/pull/18854))
* Fix a bug in `useMutableSource` that may happen when `getSnapshot` changes. ([@bvaughn](https://github.com/bvaughn) in [#18297](https://github.com/facebook/react/pull/18297))
* Fix a tearing bug in `useMutableSource`. ([@bvaughn](https://github.com/bvaughn) in [#18912](https://github.com/facebook/react/pull/18912))
* Warn if calling setState outside of render but before commit. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18838](https://github.com/facebook/react/pull/18838))

## 16.14.0 (October 14, 2020)

### React

* Add support for the [new JSX transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html). ([@lunaruan](https://github.com/lunaruan) in [#18299](https://github.com/facebook/react/pull/18299))

## 16.13.1 (March 19, 2020)

### React DOM

* Fix bug in legacy mode Suspense where effect clean-up functions are not fired. This only affects users who use Suspense for data fetching in legacy mode, which is not technically supported. ([@acdlite](https://github.com/acdlite) in [#18238](https://github.com/facebook/react/pull/18238))
* Revert warning for cross-component updates that happen inside class render lifecycles (`componentWillReceiveProps`, `shouldComponentUpdate`, and so on). ([@gaearon](https://github.com/gaearon) in [#18330](https://github.com/facebook/react/pull/18330))

## 16.13.0 (February 26, 2020)

### React

* Warn when a string ref is used in a manner that's not amenable to a future codemod ([@lunaruan](https://github.com/lunaruan) in [#17864](https://github.com/facebook/react/pull/17864))
* Deprecate `React.createFactory()` ([@trueadm](https://github.com/trueadm) in [#17878](https://github.com/facebook/react/pull/17878))

### React DOM

* Warn when changes in `style` may cause an unexpected collision ([@sophiebits](https://github.com/sophiebits) in [#14181](https://github.com/facebook/react/pull/14181), [#18002](https://github.com/facebook/react/pull/18002))
* Warn when a function component is updated during another component's render phase ([@acdlite](https://github.com/acdlite) in [#17099](https://github.com/facebook/react/pull/17099))
* Deprecate `unstable_createPortal` ([@trueadm](https://github.com/trueadm) in [#17880](https://github.com/facebook/react/pull/17880))
* Fix `onMouseEnter` being fired on disabled buttons ([@AlfredoGJ](https://github.com/AlfredoGJ) in [#17675](https://github.com/facebook/react/pull/17675))
* Call `shouldComponentUpdate` twice when developing in `StrictMode` ([@bvaughn](https://github.com/bvaughn) in [#17942](https://github.com/facebook/react/pull/17942))
* Add `version` property to ReactDOM ([@ealush](https://github.com/ealush) in [#15780](https://github.com/facebook/react/pull/15780))
* Don't call `toString()` of `dangerouslySetInnerHTML` ([@sebmarkbage](https://github.com/sebmarkbage) in [#17773](https://github.com/facebook/react/pull/17773))
* Show component stacks in more warnings ([@gaearon](https://github.com/gaearon) in [#17922](https://github.com/facebook/react/pull/17922), [#17586](https://github.com/facebook/react/pull/17586))

### Concurrent Mode (Experimental)

* Warn for problematic usages of `ReactDOM.createRoot()` ([@trueadm](https://github.com/trueadm) in [#17937](https://github.com/facebook/react/pull/17937))
* Remove `ReactDOM.createRoot()` callback params and added warnings on usage ([@bvaughn](https://github.com/bvaughn) in [#17916](https://github.com/facebook/react/pull/17916))
* Don't group Idle/Offscreen work with other work ([@sebmarkbage](https://github.com/sebmarkbage) in [#17456](https://github.com/facebook/react/pull/17456))
* Adjust `SuspenseList` CPU bound heuristic ([@sebmarkbage](https://github.com/sebmarkbage) in [#17455](https://github.com/facebook/react/pull/17455))
* Add missing event plugin priorities ([@trueadm](https://github.com/trueadm) in [#17914](https://github.com/facebook/react/pull/17914))
* Fix `isPending` only being true when transitioning from inside an input event ([@acdlite](https://github.com/acdlite) in [#17382](https://github.com/facebook/react/pull/17382))
* Fix `React.memo` components dropping updates when interrupted by a higher priority update ([@acdlite]((https://github.com/acdlite)) in [#18091](https://github.com/facebook/react/pull/18091))
* Don't warn when suspending at the wrong priority ([@gaearon](https://github.com/gaearon) in [#17971](https://github.com/facebook/react/pull/17971))
* Fix a bug with rebasing updates ([@acdlite](https://github.com/acdlite) and [@sebmarkbage](https://github.com/sebmarkbage) in [#17560](https://github.com/facebook/react/pull/17560), [#17510](https://github.com/facebook/react/pull/17510), [#17483](https://github.com/facebook/react/pull/17483), [#17480](https://github.com/facebook/react/pull/17480))

## 16.12.0 (November 14, 2019)

### React DOM

* Fix passive effects (`useEffect`) not being fired in a multi-root app. ([@acdlite](https://github.com/acdlite) in [#17347](https://github.com/facebook/react/pull/17347))

### React Is

* Fix `lazy` and `memo` types considered elements instead of components ([@bvaughn](https://github.com/bvaughn) in [#17278](https://github.com/facebook/react/pull/17278))

## 16.11.0 (October 22, 2019)

### React DOM

* Fix `mouseenter` handlers from firing twice inside nested React containers. [@yuanoook](https://github.com/yuanoook) in [#16928](https://github.com/facebook/react/pull/16928)
* Remove `unstable_createRoot` and `unstable_createSyncRoot` experimental APIs. (These are available in the Experimental channel as `createRoot` and `createSyncRoot`.) ([@acdlite](http://github.com/acdlite) in [#17088](https://github.com/facebook/react/pull/17088))

## 16.10.2 (October 3, 2019)

### React DOM

* Fix regression in react-native-web by restoring order of arguments in event plugin extractors ([@necolas](https://github.com/necolas) in [#16978](https://github.com/facebook/react/pull/16978))

## 16.10.1 (September 28, 2019)

### React DOM

* Fix regression in Next.js apps by allowing Suspense mismatch during hydration to silently proceed ([@sebmarkbage](https://github.com/sebmarkbage) in [#16943](https://github.com/facebook/react/pull/16943))

## 16.10.0 (September 27, 2019)

### React DOM

* Fix edge case where a hook update wasn't being memoized. ([@sebmarkbage](http://github.com/sebmarkbage) in [#16359](https://github.com/facebook/react/pull/16359))
* Fix heuristic for determining when to hydrate, so we don't incorrectly hydrate during an update. ([@sebmarkbage](http://github.com/sebmarkbage) in [#16739](https://github.com/facebook/react/pull/16739))
* Clear additional fiber fields during unmount to save memory. ([@trueadm](http://github.com/trueadm) in [#16807](https://github.com/facebook/react/pull/16807))
* Fix bug with required text fields in Firefox. ([@halvves](http://github.com/halvves) in [#16578](https://github.com/facebook/react/pull/16578))
* Prefer `Object.is` instead of inline polyfill, when available. ([@ku8ar](http://github.com/ku8ar) in [#16212](https://github.com/facebook/react/pull/16212))
* Fix bug when mixing Suspense and error handling. ([@acdlite](http://github.com/acdlite) in [#16801](https://github.com/facebook/react/pull/16801))


### Scheduler (Experimental)

* Improve queue performance by switching its internal data structure to a min binary heap. ([@acdlite](http://github.com/acdlite) in [#16245](https://github.com/facebook/react/pull/16245))
* Use `postMessage` loop with short intervals instead of attempting to align to frame boundaries with `requestAnimationFrame`. ([@acdlite](http://github.com/acdlite) in [#16214](https://github.com/facebook/react/pull/16214))

### useSubscription

* Avoid tearing issue when a mutation happens and the previous update is still in progress. ([@bvaughn](http://github.com/bvaughn) in [#16623](https://github.com/facebook/react/pull/16623))

## 16.9.0 (August 8, 2019)

### React

* Add `<React.Profiler>` API for gathering performance measurements programmatically. ([@bvaughn](https://github.com/bvaughn) in [#15172](https://github.com/facebook/react/pull/15172))
* Remove `unstable_ConcurrentMode` in favor of `unstable_createRoot`. ([@acdlite](https://github.com/acdlite) in [#15532](https://github.com/facebook/react/pull/15532))

### React DOM

* Deprecate old names for the `UNSAFE_*` lifecycle methods. ([@bvaughn](https://github.com/bvaughn) in [#15186](https://github.com/facebook/react/pull/15186) and [@threepointone](https://github.com/threepointone) in [#16103](https://github.com/facebook/react/pull/16103))
* Deprecate `javascript:` URLs as a common attack surface. ([@sebmarkbage](https://github.com/sebmarkbage) in [#15047](https://github.com/facebook/react/pull/15047))
* Deprecate uncommon "module pattern" (factory) components. ([@sebmarkbage](https://github.com/sebmarkbage) in [#15145](https://github.com/facebook/react/pull/15145))
* Add support for the `disablePictureInPicture` attribute on `<video>`. ([@eek](https://github.com/eek) in [#15334](https://github.com/facebook/react/pull/15334))
* Add support for `onLoad` event for `<embed>`. ([@cherniavskii](https://github.com/cherniavskii) in [#15614](https://github.com/facebook/react/pull/15614))
* Add support for editing `useState` state from DevTools. ([@bvaughn](https://github.com/bvaughn) in [#14906](https://github.com/facebook/react/pull/14906))
* Add support for toggling Suspense from DevTools. ([@gaearon](https://github.com/gaearon) in [#15232](https://github.com/facebook/react/pull/15232))
* Warn when `setState` is called from `useEffect`, creating a loop. ([@gaearon](https://github.com/gaearon) in [#15180](https://github.com/facebook/react/pull/15180))
* Fix a memory leak. ([@paulshen](https://github.com/paulshen) in [#16115](https://github.com/facebook/react/pull/16115))
* Fix a crash inside `findDOMNode` for components wrapped in `<Suspense>`. ([@acdlite](https://github.com/acdlite) in [#15312](https://github.com/facebook/react/pull/15312))
* Fix pending effects from being flushed too late. ([@acdlite](https://github.com/acdlite) in [#15650](https://github.com/facebook/react/pull/15650))
* Fix incorrect argument order in a warning message. ([@brickspert](https://github.com/brickspert) in [#15345](https://github.com/facebook/react/pull/15345))
* Fix hiding Suspense fallback nodes when there is an `!important` style. ([@acdlite](https://github.com/acdlite) in [#15861](https://github.com/facebook/react/pull/15861) and [#15882](https://github.com/facebook/react/pull/15882))
* Slightly improve hydration performance. ([@bmeurer](https://github.com/bmeurer) in [#15998](https://github.com/facebook/react/pull/15998))

### React DOM Server

* Fix incorrect output for camelCase custom CSS property names. ([@bedakb](https://github.com/bedakb) in [#16167](https://github.com/facebook/react/pull/16167))

### React Test Utilities and Test Renderer

* Add `act(async () => ...)` for testing asynchronous state updates. ([@threepointone](https://github.com/threepointone) in [#14853](https://github.com/facebook/react/pull/14853))
* Add support for nesting `act` from different renderers. ([@threepointone](https://github.com/threepointone) in [#16039](https://github.com/facebook/react/pull/16039) and [#16042](https://github.com/facebook/react/pull/16042))
* Warn in Strict Mode if effects are scheduled outside an `act()` call. ([@threepointone](https://github.com/threepointone) in [#15763](https://github.com/facebook/react/pull/15763) and [#16041](https://github.com/facebook/react/pull/16041))
* Warn when using `act` from the wrong renderer. ([@threepointone](https://github.com/threepointone) in [#15756](https://github.com/facebook/react/pull/15756))

### ESLint Plugin: React Hooks

* Report Hook calls at the top level as a violation. ([gaearon](https://github.com/gaearon) in [#16455](https://github.com/facebook/react/pull/16455))

## 16.8.6 (March 27, 2019)

### React DOM

* Fix an incorrect bailout in `useReducer()`. ([@acdlite](https://github.com/acdlite) in [#15124](https://github.com/facebook/react/pull/15124))
* Fix iframe warnings in Safari DevTools. ([@renanvalentin](https://github.com/renanvalentin) in [#15099](https://github.com/facebook/react/pull/15099))
* Warn if `contextType` is set to `Context.Consumer` instead of `Context`. ([@aweary](https://github.com/aweary) in [#14831](https://github.com/facebook/react/pull/14831))
* Warn if `contextType` is set to invalid values. ([@gaearon](https://github.com/gaearon) in [#15142](https://github.com/facebook/react/pull/15142))

## 16.8.5 (March 22, 2019)

### React DOM

* Don't set the first option as selected in select tag with `size` attribute. ([@kulek1](https://github.com/kulek1) in [#14242](https://github.com/facebook/react/pull/14242))
* Improve the `useEffect(async () => ...)` warning message. ([@gaearon](https://github.com/gaearon) in [#15118](https://github.com/facebook/react/pull/15118))
* Improve the error message sometimes caused by duplicate React. ([@jaredpalmer](https://github.com/jaredpalmer) in [#15139](https://github.com/facebook/react/pull/15139))

### React DOM Server

* Improve the `useLayoutEffect` warning message when server rendering. ([@gaearon](https://github.com/gaearon) in [#15158](https://github.com/facebook/react/pull/15158))

### React Shallow Renderer

* Fix `setState` in shallow renderer to work with Hooks. ([@gaearon](https://github.com/gaearon) in [#15120](https://github.com/facebook/react/pull/15120))
* Fix shallow renderer to support `React.memo`. ([@aweary](https://github.com/aweary) in [#14816](https://github.com/facebook/react/pull/14816))
* Fix shallow renderer to support Hooks inside `forwardRef`. ([@eps1lon](https://github.com/eps1lon) in [#15100](https://github.com/facebook/react/pull/15100))

## 16.8.4 (March 5, 2019)

### React DOM and other renderers

- Fix a bug where DevTools caused a runtime error when inspecting a component that used a `useContext` hook. ([@bvaughn](https://github.com/bvaughn) in [#14940](https://github.com/facebook/react/pull/14940))

## 16.8.3 (February 21, 2019)

### React DOM

* Fix a bug that caused inputs to behave incorrectly in UMD builds. ([@gaearon](https://github.com/gaearon) in [#14914](https://github.com/facebook/react/pull/14914))
* Fix a bug that caused render phase updates to be discarded. ([@gaearon](https://github.com/gaearon) in [#14852](https://github.com/facebook/react/pull/14852))

### React DOM Server
* Unwind the context stack when a stream is destroyed without completing, to prevent incorrect values during a subsequent render. ([@overlookmotel](https://github.com/overlookmotel) in [#14706](https://github.com/facebook/react/pull/14706/))

### ESLint Plugin for React Hooks

* Add a new recommended `exhaustive-deps` rule. ([@gaearon](https://github.com/gaearon) in [#14636](https://github.com/facebook/react/pull/14636))

## 16.8.2 (February 14, 2019)

### React DOM

* Fix `ReactDOM.render` being ignored inside `useEffect`. ([@gaearon](https://github.com/gaearon) in [#14799](https://github.com/facebook/react/pull/14799))
* Fix a crash when unmounting empty portals. ([@gaearon](https://github.com/gaearon) in [#14820](https://github.com/facebook/react/pull/14820))
* Fix `useImperativeHandle` to work correctly when no deps are specified. ([@gaearon](https://github.com/gaearon) in [#14801](https://github.com/facebook/react/pull/14801))
* Fix `crossOrigin` attribute to work in SVG `image` elements. ([@aweary](https://github.com/aweary) in [#14832](https://github.com/facebook/react/pull/14832))
* Fix a false positive warning when using Suspense with Hooks. ([@gaearon](https://github.com/gaearon) in [#14821](https://github.com/facebook/react/pull/14821))

### React Test Utils and React Test Renderer

* Include component stack into the `act()` warning. ([@threepointone](https://github.com/threepointone) in [#14855](https://github.com/facebook/react/pull/14855))

## 16.8.1 (February 6, 2019)

### React DOM and React Test Renderer

* Fix a crash when used together with an older version of React. ([@bvaughn](https://github.com/bvaughn) in [#14770](https://github.com/facebook/react/pull/14770))

### React Test Utils

* Fix a crash in Node environment. ([@threepointone](https://github.com/threepointone) in [#14768](https://github.com/facebook/react/pull/14768))

## 16.8.0 (February 6, 2019)

### React

* Add [Hooks](https://reactjs.org/docs/hooks-intro.html) — a way to use state and other React features without writing a class. ([@acdlite](https://github.com/acdlite) et al. in [#13968](https://github.com/facebook/react/pull/13968))
* Improve the `useReducer` Hook lazy initialization API. ([@acdlite](https://github.com/acdlite) in [#14723](https://github.com/facebook/react/pull/14723))

### React DOM

* Bail out of rendering on identical values for `useState` and `useReducer` Hooks. ([@acdlite](https://github.com/acdlite) in [#14569](https://github.com/facebook/react/pull/14569))
* Use `Object.is` algorithm for comparing `useState` and `useReducer` values. ([@Jessidhia](https://github.com/Jessidhia) in [#14752](https://github.com/facebook/react/pull/14752))
* Don’t compare the first argument passed to `useEffect`/`useMemo`/`useCallback` Hooks. ([@acdlite](https://github.com/acdlite) in [#14594](https://github.com/facebook/react/pull/14594))
* Support synchronous thenables passed to `React.lazy()`. ([@gaearon](https://github.com/gaearon) in [#14626](https://github.com/facebook/react/pull/14626))
* Render components with Hooks twice in Strict Mode (DEV-only) to match class behavior. ([@gaearon](https://github.com/gaearon) in [#14654](https://github.com/facebook/react/pull/14654))
* Warn about mismatching Hook order in development. ([@threepointone](https://github.com/threepointone) in [#14585](https://github.com/facebook/react/pull/14585) and [@acdlite](https://github.com/acdlite) in [#14591](https://github.com/facebook/react/pull/14591))
* Effect clean-up functions must return either `undefined` or a function. All other values, including `null`, are not allowed. [@acdlite](https://github.com/acdlite) in [#14119](https://github.com/facebook/react/pull/14119)

### React Test Renderer and Test Utils

* Support Hooks in the shallow renderer. ([@trueadm](https://github.com/trueadm) in [#14567](https://github.com/facebook/react/pull/14567))
* Fix wrong state in `shouldComponentUpdate` in the presence of `getDerivedStateFromProps` for Shallow Renderer. ([@chenesan](https://github.com/chenesan) in [#14613](https://github.com/facebook/react/pull/14613))
* Add `ReactTestRenderer.act()` and `ReactTestUtils.act()` for batching updates so that tests more closely match real behavior. ([@threepointone](https://github.com/threepointone) in [#14744](https://github.com/facebook/react/pull/14744))


### ESLint Plugin: React Hooks

* Initial [release](https://www.npmjs.com/package/eslint-plugin-react-hooks). ([@calebmer](https://github.com/calebmer) in [#13968](https://github.com/facebook/react/pull/13968))
* Fix reporting after encountering a loop. ([@calebmer](https://github.com/calebmer) and [@Yurickh](https://github.com/Yurickh) in [#14661](https://github.com/facebook/react/pull/14661))
* Don't consider throwing to be a rule violation. ([@sophiebits](https://github.com/sophiebits) in [#14040](https://github.com/facebook/react/pull/14040))

## 16.7.0 (December 19, 2018)

### React DOM

* Fix performance of `React.lazy` for large numbers of lazily-loaded components. ([@acdlite](http://github.com/acdlite) in [#14429](https://github.com/facebook/react/pull/14429))
* Clear fields on unmount to avoid memory leaks. ([@trueadm](http://github.com/trueadm) in [#14276](https://github.com/facebook/react/pull/14276))
* Fix bug with SSR and context when mixing `react-dom/server@16.6` and `react@<16.6`. ([@gaearon](http://github.com/gaearon) in [#14291](https://github.com/facebook/react/pull/14291))
* Fix a performance regression in profiling mode. ([@bvaughn](http://github.com/bvaughn) in [#14383](https://github.com/facebook/react/pull/14383))

### Scheduler (Experimental)

* Post to MessageChannel instead of window. ([@acdlite](http://github.com/acdlite) in [#14234](https://github.com/facebook/react/pull/14234))
* Reduce serialization overhead. ([@developit](http://github.com/developit) in [#14249](https://github.com/facebook/react/pull/14249))
* Fix fallback to `setTimeout` in testing environments. ([@bvaughn](http://github.com/bvaughn) in [#14358](https://github.com/facebook/react/pull/14358))
* Add methods for debugging. ([@mrkev](http://github.com/mrkev) in [#14053](https://github.com/facebook/react/pull/14053))


## 16.6.3 (November 12, 2018)

### React DOM

* Fix bugs in `Suspense` and `lazy`. ([@acdlite](https://github.com/acdlite) in [#14133](https://github.com/facebook/react/pull/14133), [#14157](https://github.com/facebook/react/pull/14157), and [#14164](https://github.com/facebook/react/pull/14164))
* Fix highlighting of `React.memo` updates in React DevTools. ([@bvaughn](https://github.com/bvaughn) in [#14141](https://github.com/facebook/react/pull/14141))
* Fix interaction of Suspense with the React Profiler. ([@bvaughn](https://github.com/bvaughn) in [#14065](https://github.com/facebook/react/pull/14065))
* Fix a false positive warning when using Suspense. ([@acdlite](https://github.com/acdlite) in [#14158](https://github.com/facebook/react/pull/14158))

### React DOM Server

* Fix incorrect sharing of context state between `renderToNodeStream()` calls. ([@sebmarkbage](https://github.com/sebmarkbage) in [#14182](https://github.com/facebook/react/pull/14182))
* Add a warning about incorrect usage of the context API. ([@trueadm](https://github.com/trueadm) in [#14033](https://github.com/facebook/react/pull/14033))

## 16.6.2 (November 12, 2018)

This release was published in a broken state and should be skipped.

## 16.6.1 (November 6, 2018)

### React DOM

* Fallback should not remount every time a promise resolves. ([@acdlite](https://github.com/acdlite) in [#14083](https://github.com/facebook/react/pull/14083))
* Fix bug where Suspense keeps showing fallback even after everything finishes loading. ([@acdlite](https://github.com/acdlite) in [#14083](https://github.com/facebook/react/pull/14083))
* Fix a crash when Suspense finishes loading in IE11. ([@sophiebits](https://github.com/sophiebits) in [#14126](https://github.com/facebook/react/pull/14126))
* Fix unresolved default props in lifecycle methods of a lazy component. ([@gaearon](https://github.com/gaearon) in [#14112](https://github.com/facebook/react/pull/14112))
* Fix bug when recovering from an error thrown during complete phase. ([@gaearon](https://github.com/gaearon) in [#14104](https://github.com/facebook/react/pull/14104))

### Scheduler (Experimental)

* Switch from deadline object to `shouldYield` API. ([@acdlite](https://github.com/acdlite) in [#14025](https://github.com/facebook/react/pull/14025))


## 16.6.0 (October 23, 2018)

### React

* Add `React.memo()` as an alternative to `PureComponent` for functions. ([@acdlite](https://github.com/acdlite) in [#13748](https://github.com/facebook/react/pull/13748))
* Add `React.lazy()` for code splitting components. ([@acdlite](https://github.com/acdlite) in [#13885](https://github.com/facebook/react/pull/13885))
* `React.StrictMode` now warns about legacy context API. ([@bvaughn](https://github.com/bvaughn) in [#13760](https://github.com/facebook/react/pull/13760))
* `React.StrictMode` now warns about `findDOMNode`. ([@sebmarkbage](https://github.com/sebmarkbage) in [#13841](https://github.com/facebook/react/pull/13841))
* Rename `unstable_AsyncMode` to `unstable_ConcurrentMode`. ([@trueadm](https://github.com/trueadm) in [#13732](https://github.com/facebook/react/pull/13732))
* Rename `unstable_Placeholder` to `Suspense`, and `delayMs` to `maxDuration`. ([@gaearon](https://github.com/gaearon) in [#13799](https://github.com/facebook/react/pull/13799) and [@sebmarkbage](https://github.com/sebmarkbage) in [#13922](https://github.com/facebook/react/pull/13922))

### React DOM

* Add `contextType` as a more ergonomic way to subscribe to context from a class. ([@bvaughn](https://github.com/bvaughn) in [#13728](https://github.com/facebook/react/pull/13728))
* Add `getDerivedStateFromError` lifecycle method for catching errors in a future asynchronous server-side renderer. ([@bvaughn](https://github.com/bvaughn) in [#13746](https://github.com/facebook/react/pull/13746))
* Warn when `<Context>` is used instead of `<Context.Consumer>`. ([@trueadm](https://github.com/trueadm) in [#13829](https://github.com/facebook/react/pull/13829))
* Fix gray overlay on iOS Safari. ([@philipp-spiess](https://github.com/philipp-spiess) in [#13778](https://github.com/facebook/react/pull/13778))
* Fix a bug caused by overwriting `window.event` in development. ([@sergei-startsev](https://github.com/sergei-startsev) in [#13697](https://github.com/facebook/react/pull/13697))

### React DOM Server

* Add support for `React.memo()`. ([@alexmckenley](https://github.com/alexmckenley) in [#13855](https://github.com/facebook/react/pull/13855))
* Add support for `contextType`. ([@alexmckenley](https://github.com/alexmckenley) and [@sebmarkbage](https://github.com/sebmarkbage) in [#13889](https://github.com/facebook/react/pull/13889))

### Scheduler (Experimental)

* Rename the package to `scheduler`. ([@gaearon](https://github.com/gaearon) in [#13683](https://github.com/facebook/react/pull/13683))
* Support priority levels, continuations, and wrapped callbacks. ([@acdlite](https://github.com/acdlite) in [#13720](https://github.com/facebook/react/pull/13720) and [#13842](https://github.com/facebook/react/pull/13842))
* Improve the fallback mechanism in non-DOM environments. ([@acdlite](https://github.com/acdlite) in [#13740](https://github.com/facebook/react/pull/13740))
* Schedule `requestAnimationFrame` earlier. ([@acdlite](https://github.com/acdlite) in [#13785](https://github.com/facebook/react/pull/13785))
* Fix the DOM detection to be more thorough. ([@trueadm](https://github.com/trueadm) in [#13731](https://github.com/facebook/react/pull/13731))
* Fix bugs with interaction tracing. ([@bvaughn](https://github.com/bvaughn) in [#13590](https://github.com/facebook/react/pull/13590))
* Add the `envify` transform to the package. ([@mridgway](https://github.com/mridgway) in [#13766](https://github.com/facebook/react/pull/13766))

## 16.5.2 (September 18, 2018)

### React DOM

* Fixed a recent `<iframe>` regression ([@JSteunou](https://github.com/JSteunou) in [#13650](https://github.com/facebook/react/pull/13650))
* Fix `updateWrapper` so that `<textarea>`s no longer re-render when data is unchanged ([@joelbarbosa](https://github.com/joelbarbosa) in [#13643](https://github.com/facebook/react/pull/13643))

### Schedule (Experimental)

* Renaming "tracking" API to "tracing" ([@bvaughn](https://github.com/bvaughn) in [#13641](https://github.com/facebook/react/pull/13641))
* Add UMD production+profiling entry points ([@bvaughn](https://github.com/bvaughn) in [#13642](https://github.com/facebook/react/pull/13642))
* Refactored `schedule` to remove some React-isms and improve performance for when deferred updates time out ([@acdlite](https://github.com/acdlite) in [#13582](https://github.com/facebook/react/pull/13582))

## 16.5.1 (September 13, 2018)

### React

* Improve the warning when `React.forwardRef` receives an unexpected number of arguments. ([@andresroberto](https://github.com/andresroberto) in [#13636](https://github.com/facebook/react/issues/13636))

### React DOM

* Fix a regression in unstable exports used by React Native Web. ([@aweary](https://github.com/aweary) in [#13598](https://github.com/facebook/react/issues/13598))
* Fix a crash when component defines a method called `isReactComponent`. ([@gaearon](https://github.com/gaearon) in [#13608](https://github.com/facebook/react/issues/13608))
* Fix a crash in development mode in IE9 when printing a warning. ([@link-alex](https://github.com/link-alex) in [#13620](https://github.com/facebook/react/issues/13620))
* Provide a better error message when running `react-dom/profiling` with `schedule/tracking`. ([@bvaughn](https://github.com/bvaughn) in [#13605](https://github.com/facebook/react/issues/13605))
* If a `ForwardRef` component defines a `displayName`, use it in warnings. ([@probablyup](https://github.com/probablyup) in [#13615](https://github.com/facebook/react/issues/13615))

### Schedule (Experimental)

* Add a separate profiling entry point at `schedule/tracking-profiling`. ([@bvaughn](https://github.com/bvaughn) in [#13605](https://github.com/facebook/react/issues/13605))

## 16.5.0 (September 5, 2018)

### React

* Add a warning if `React.forwardRef` render function doesn't take exactly two arguments ([@bvaughn](https://github.com/bvaughn) in [#13168](https://github.com/facebook/react/issues/13168))
* Improve the error message when passing an element to `createElement` by mistake ([@DCtheTall](https://github.com/DCtheTall) in [#13131](https://github.com/facebook/react/issues/13131))
* Don't call profiler `onRender` until after mutations ([@bvaughn](https://github.com/bvaughn) in [#13572](https://github.com/facebook/react/issues/13572))

### React DOM

* Add support for React DevTools Profiler ([@bvaughn](https://github.com/bvaughn) in [#13058](https://github.com/facebook/react/issues/13058))
* Add `react-dom/profiling` entry point alias for profiling in production ([@bvaughn](https://github.com/bvaughn) in [#13570](https://github.com/facebook/react/issues/13570))
* Add `onAuxClick` event for browsers that support it ([@jquense](https://github.com/jquense) in [#11571](https://github.com/facebook/react/issues/11571))
* Add `movementX` and `movementY` fields to mouse events ([@jasonwilliams](https://github.com/jasonwilliams) in [#9018](https://github.com/facebook/react/issues/9018))
* Add `tangentialPressure` and `twist` fields to pointer events ([@motiz88](https://github.com/motiz88) in [#13374](https://github.com/facebook/react/issues/13374))
* Minimally support iframes (nested browsing contexts) in selection event handling ([@acusti](https://github.com/acusti) in [#12037](https://github.com/facebook/react/issues/12037))
* Support passing booleans to the `focusable` SVG attribute ([@gaearon](https://github.com/gaearon) in [#13339](https://github.com/facebook/react/issues/13339))
* Ignore `<noscript>` on the client when hydrating ([@Ephem](https://github.com/Ephem) in [#13537](https://github.com/facebook/react/issues/13537))
* Fix `gridArea` to be treated as a unitless CSS property ([@mgol](https://github.com/mgol) in [#13550](https://github.com/facebook/react/issues/13550))
* Fix incorrect data in `compositionend` event when typing Korean on IE11 ([@crux153](https://github.com/crux153) in [#12563](https://github.com/facebook/react/issues/12563))
* Fix a crash when using dynamic `children` in the `<option>` tag ([@Slowyn](https://github.com/Slowyn) in [#13261](https://github.com/facebook/react/issues/13261), [@gaearon](https://github.com/gaearon) in [#13465](https://github.com/facebook/react/pull/13465))
* Fix the `checked` attribute not getting initially set on the `input` ([@dilidili](https://github.com/dilidili) in [#13114](https://github.com/facebook/react/issues/13114))
* Fix hydration of `dangerouslySetInnerHTML` when `__html` is not a string ([@gaearon](https://github.com/gaearon) in [#13353](https://github.com/facebook/react/issues/13353))
* Fix a warning about missing controlled `onChange` to fire on falsy values too ([@nicolevy](https://github.com/nicolevy) in [#12628](https://github.com/facebook/react/issues/12628))
* Fix `submit` and `reset` buttons getting an empty label ([@ellsclytn](https://github.com/ellsclytn) in [#12780](https://github.com/facebook/react/issues/12780))
* Fix the `onSelect` event not being triggered after drag and drop ([@gaearon](https://github.com/gaearon) in [#13422](https://github.com/facebook/react/issues/13422))
* Fix the `onClick` event not working inside a portal on iOS ([@aweary](https://github.com/aweary) in [#11927](https://github.com/facebook/react/issues/11927))
* Fix a performance issue when thousands of roots are re-rendered ([@gaearon](https://github.com/gaearon) in [#13335](https://github.com/facebook/react/issues/13335))
* Fix a performance regression that also caused `onChange` to not fire in some cases ([@gaearon](https://github.com/gaearon) in [#13423](https://github.com/facebook/react/issues/13423))
* Handle errors in more edge cases gracefully ([@gaearon](https://github.com/gaearon) in [#13237](https://github.com/facebook/react/issues/13237) and [@acdlite](https://github.com/acdlite) in [#13269](https://github.com/facebook/react/issues/13269))
* Don't use proxies for synthetic events in development ([@gaearon](https://github.com/gaearon) in [#12171](https://github.com/facebook/react/issues/12171))
* Warn when `"false"` or `"true"` is the value of a boolean DOM prop ([@motiz88](https://github.com/motiz88) in [#13372](https://github.com/facebook/react/issues/13372))
* Warn when `this.state` is initialized to `props` ([@veekas](https://github.com/veekas) in [#11658](https://github.com/facebook/react/issues/11658))
* Don't compare `style` on hydration in IE due to noisy false positives ([@mgol](https://github.com/mgol) in [#13534](https://github.com/facebook/react/issues/13534))
* Include `StrictMode` in the component stack ([@gaearon](https://github.com/gaearon) in [#13240](https://github.com/facebook/react/issues/13240))
* Don't overwrite `window.event` in IE ([@ConradIrwin](https://github.com/ConradIrwin) in [#11696](https://github.com/facebook/react/issues/11696))
* Improve component stack for the `folder/index.js` naming convention ([@gaearon](https://github.com/gaearon) in [#12059](https://github.com/facebook/react/issues/12059))
* Improve a warning when using `getDerivedStateFromProps` without initialized state ([@flxwu](https://github.com/flxwu) in [#13317](https://github.com/facebook/react/issues/13317))
* Improve a warning about invalid textarea usage ([@raunofreiberg](https://github.com/raunofreiberg) in [#13361](https://github.com/facebook/react/issues/13361))
* Treat invalid Symbol and function values more consistently ([@raunofreiberg](https://github.com/raunofreiberg) in [#13362](https://github.com/facebook/react/issues/13362) and [#13389](https://github.com/facebook/react/issues/13389))
* Allow Electron `<webview>` tag without warnings ([@philipp-spiess](https://github.com/philipp-spiess) in [#13301](https://github.com/facebook/react/issues/13301))
* Don't show the uncaught error addendum if `e.preventDefault()` was called ([@gaearon](https://github.com/gaearon) in [#13384](https://github.com/facebook/react/issues/13384))
* Warn about rendering Generators ([@gaearon](https://github.com/gaearon) in [#13312](https://github.com/facebook/react/issues/13312))
* Remove irrelevant suggestion of a legacy method from a warning ([@zx6658](https://github.com/zx6658) in [#13169](https://github.com/facebook/react/issues/13169))
* Remove `unstable_deferredUpdates` in favor of `unstable_scheduleWork` from `schedule` ([@gaearon](https://github.com/gaearon) in [#13488](https://github.com/facebook/react/issues/13488))
* Fix unstable asynchronous mode from doing unnecessary work when an update takes too long ([@acdlite](https://github.com/acdlite) in [#13503](https://github.com/facebook/react/issues/13503))

### React DOM Server

* Fix crash with nullish children when using `dangerouslySetInnerHtml` in a selected `<option>` ([@mridgway](https://github.com/mridgway) in [#13078](https://github.com/facebook/react/issues/13078))
* Fix crash when `setTimeout` is missing ([@dustinsoftware](https://github.com/dustinsoftware) in [#13088](https://github.com/facebook/react/issues/13088))

### React Test Renderer and Test Utils

* Fix `this` in a functional component for shallow renderer to be `undefined` ([@koba04](https://github.com/koba04) in [#13144](https://github.com/facebook/react/issues/13144))
* Deprecate a Jest-specific `ReactTestUtils.mockComponent()` helper ([@bvaughn](https://github.com/bvaughn) in [#13193](https://github.com/facebook/react/issues/13193))
* Warn about `ReactDOM.createPortal` usage within the test renderer ([@bvaughn](https://github.com/bvaughn) in [#12895](https://github.com/facebook/react/issues/12895))
* Improve a confusing error message ([@gaearon](https://github.com/gaearon) in [#13351](https://github.com/facebook/react/issues/13351))

### React ART

* Add support for DevTools ([@yunchancho](https://github.com/yunchancho) in [#13173](https://github.com/facebook/react/issues/13173))

### Schedule (Experimental)

* New package for cooperatively scheduling work in a browser environment. It's used by React internally, but its public API is not finalized yet. ([@flarnie](https://github.com/flarnie) in [#12624](https://github.com/facebook/react/pull/12624))

## 16.4.2 (August 1, 2018)

### React DOM Server

* Fix a [potential XSS vulnerability when the attacker controls an attribute name](https://reactjs.org/blog/2018/08/01/react-v-16-4-2.html) (`CVE-2018-6341`). This fix is available in the latest `react-dom@16.4.2`, as well as in previous affected minor versions: `react-dom@16.0.1`, `react-dom@16.1.2`, `react-dom@16.2.1`, and `react-dom@16.3.3`. ([@gaearon](https://github.com/gaearon) in [#13302](https://github.com/facebook/react/pull/13302))

* Fix a crash in the server renderer when an attribute is called `hasOwnProperty`. This fix is only available in `react-dom@16.4.2`. ([@gaearon](https://github.com/gaearon) in [#13303](https://github.com/facebook/react/pull/13303))

## 16.4.1 (June 13, 2018)

### React

* You can now assign `propTypes` to components returned by `React.ForwardRef`. ([@bvaughn](https://github.com/bvaughn) in [#12911](https://github.com/facebook/react/pull/12911))

### React DOM

* Fix a crash when the input `type` changes from some other types to `text`. ([@spirosikmd](https://github.com/spirosikmd) in [#12135](https://github.com/facebook/react/pull/12135))
* Fix a crash in IE11 when restoring focus to an SVG element. ([@ThaddeusJiang](https://github.com/ThaddeusJiang) in [#12996](https://github.com/facebook/react/pull/12996))
* Fix a range input not updating in some cases. ([@Illu](https://github.com/Illu) in [#12939](https://github.com/facebook/react/pull/12939))
* Fix input validation triggering unnecessarily in Firefox. ([@nhunzaker](https://github.com/nhunzaker) in [#12925](https://github.com/facebook/react/pull/12925))
* Fix an incorrect `event.target` value for the `onChange` event in IE9. ([@nhunzaker](https://github.com/nhunzaker) in [#12976](https://github.com/facebook/react/pull/12976))
* Fix a false positive error when returning an empty `<React.Fragment />` from a component. ([@philipp-spiess](https://github.com/philipp-spiess) in [#12966](https://github.com/facebook/react/pull/12966))

### React DOM Server

* Fix an incorrect value being provided by new context API. ([@ericsoderberghp](https://github.com/ericsoderberghp) in [#12985](https://github.com/facebook/react/pull/12985), [@gaearon](https://github.com/gaearon) in [#13019](https://github.com/facebook/react/pull/13019))

### React Test Renderer

* Allow multiple root children in test renderer traversal API. ([@gaearon](https://github.com/gaearon) in [#13017](https://github.com/facebook/react/pull/13017))
* Fix `getDerivedStateFromProps()` in the shallow renderer to not discard the pending state. ([@fatfisz](https://github.com/fatfisz) in [#13030](https://github.com/facebook/react/pull/13030))

## 16.4.0 (May 23, 2018)

### React

* Add a new [experimental](https://github.com/reactjs/rfcs/pull/51) `React.unstable_Profiler` component for measuring performance. ([@bvaughn](https://github.com/bvaughn) in [#12745](https://github.com/facebook/react/pull/12745))

### React DOM

* Add support for the Pointer Events specification. ([@philipp-spiess](https://github.com/philipp-spiess) in [#12507](https://github.com/facebook/react/pull/12507))
* Properly call `getDerivedStateFromProps()` regardless of the reason for re-rendering. ([@acdlite](https://github.com/acdlite) in [#12600](https://github.com/facebook/react/pull/12600) and [#12802](https://github.com/facebook/react/pull/12802))
* Fix a bug that prevented context propagation in some cases. ([@gaearon](https://github.com/gaearon) in [#12708](https://github.com/facebook/react/pull/12708))
* Fix re-rendering of components using `forwardRef()` on a deeper `setState()`. ([@gaearon](https://github.com/gaearon) in [#12690](https://github.com/facebook/react/pull/12690))
* Fix some attributes incorrectly getting removed from custom element nodes. ([@airamrguez](https://github.com/airamrguez) in [#12702](https://github.com/facebook/react/pull/12702))
* Fix context providers to not bail out on children if there's a legacy context provider above. ([@gaearon](https://github.com/gaearon) in [#12586](https://github.com/facebook/react/pull/12586))
* Add the ability to specify `propTypes` on a context provider component. ([@nicolevy](https://github.com/nicolevy) in [#12658](https://github.com/facebook/react/pull/12658))
* Fix a false positive warning when using `react-lifecycles-compat` in `<StrictMode>`. ([@bvaughn](https://github.com/bvaughn) in [#12644](https://github.com/facebook/react/pull/12644))
* Warn when the `forwardRef()` render function has `propTypes` or `defaultProps`. ([@bvaughn](https://github.com/bvaughn) in [#12644](https://github.com/facebook/react/pull/12644))
* Improve how `forwardRef()` and context consumers are displayed in the component stack. ([@sophiebits](https://github.com/sophiebits) in [#12777](https://github.com/facebook/react/pull/12777))
* Change internal event names. This can break third-party packages that rely on React internals in unsupported ways. ([@philipp-spiess](https://github.com/philipp-spiess) in [#12629](https://github.com/facebook/react/pull/12629))

### React Test Renderer

* Fix the `getDerivedStateFromProps()` support to match the new React DOM behavior. ([@koba04](https://github.com/koba04) in [#12676](https://github.com/facebook/react/pull/12676))
* Fix a `testInstance.parent` crash when the parent is a fragment or another special node. ([@gaearon](https://github.com/gaearon) in [#12813](https://github.com/facebook/react/pull/12813))
* `forwardRef()` components are now discoverable by the test renderer traversal methods. ([@gaearon](https://github.com/gaearon) in [#12725](https://github.com/facebook/react/pull/12725))
* Shallow renderer now ignores `setState()` updaters that return `null` or `undefined`. ([@koba04](https://github.com/koba04) in [#12756](https://github.com/facebook/react/pull/12756))

### React ART

* Fix reading context provided from the tree managed by React DOM. ([@acdlite](https://github.com/acdlite) in [#12779](https://github.com/facebook/react/pull/12779))

### React Call Return (Experimental)

* This experiment was deleted because it was affecting the bundle size and the API wasn't good enough. It's likely to come back in the future in some other form. ([@gaearon](https://github.com/gaearon) in [#12820](https://github.com/facebook/react/pull/12820))

### React Reconciler (Experimental)

* The [new host config shape](https://github.com/facebook/react/blob/c601f7a64640290af85c9f0e33c78480656b46bc/packages/react-noop-renderer/src/createReactNoop.js#L82-L285) is flat and doesn't use nested objects. ([@gaearon](https://github.com/gaearon) in [#12792](https://github.com/facebook/react/pull/12792))

## 16.3.3 (August 1, 2018)

### React DOM Server

* Fix a [potential XSS vulnerability when the attacker controls an attribute name](https://reactjs.org/blog/2018/08/01/react-v-16-4-2.html) (`CVE-2018-6341`). This fix is available in the latest `react-dom@16.4.2`, as well as in previous affected minor versions: `react-dom@16.0.1`, `react-dom@16.1.2`, `react-dom@16.2.1`, and `react-dom@16.3.3`. ([@gaearon](https://github.com/gaearon) in [#13302](https://github.com/facebook/react/pull/13302))

## 16.3.2 (April 16, 2018)

### React

* Improve the error message when passing `null` or `undefined` to `React.cloneElement`. ([@nicolevy](https://github.com/nicolevy) in [#12534](https://github.com/facebook/react/pull/12534))

### React DOM

* Fix an IE crash in development when using `<StrictMode>`. ([@bvaughn](https://github.com/bvaughn) in [#12546](https://github.com/facebook/react/pull/12546))
* Fix labels in User Timing measurements for new component types. ([@bvaughn](https://github.com/bvaughn) in [#12609](https://github.com/facebook/react/pull/12609))
* Improve the warning about wrong component type casing. ([@nicolevy](https://github.com/nicolevy) in [#12533](https://github.com/facebook/react/pull/12533))
* Improve general performance in development mode. ([@gaearon](https://github.com/gaearon) in [#12537](https://github.com/facebook/react/pull/12537))
* Improve performance of the experimental `unstable_observedBits` API with nesting. ([@gaearon](https://github.com/gaearon) in [#12543](https://github.com/facebook/react/pull/12543))

### React Test Renderer

* Add a UMD build. ([@bvaughn](https://github.com/bvaughn) in [#12594](https://github.com/facebook/react/pull/12594))

## 16.3.1 (April 3, 2018)

### React

* Fix a false positive warning in IE11 when using `Fragment`. ([@heikkilamarko](https://github.com/heikkilamarko) in [#12504](https://github.com/facebook/react/pull/12504))
* Prefix a private API. ([@Andarist](https://github.com/Andarist) in [#12501](https://github.com/facebook/react/pull/12501))
* Improve the warning when calling `setState()` in constructor. ([@gaearon](https://github.com/gaearon) in [#12532](https://github.com/facebook/react/pull/12532))

### React DOM

* Fix `getDerivedStateFromProps()` not getting applied in some cases. ([@acdlite](https://github.com/acdlite) in [#12528](https://github.com/facebook/react/pull/12528))
* Fix a performance regression in development mode. ([@gaearon](https://github.com/gaearon) in [#12510](https://github.com/facebook/react/pull/12510))
* Fix error handling bugs in development mode. ([@gaearon](https://github.com/gaearon) and [@acdlite](https://github.com/acdlite) in [#12508](https://github.com/facebook/react/pull/12508))
* Improve user timing API messages for profiling. ([@flarnie](https://github.com/flarnie) in [#12384](https://github.com/facebook/react/pull/12384))

### Create Subscription

* Set the package version to be in sync with React releases. ([@bvaughn](https://github.com/bvaughn) in [#12526](https://github.com/facebook/react/pull/12526))
* Add a peer dependency on React 16.3+. ([@NMinhNguyen](https://github.com/NMinhNguyen) in [#12496](https://github.com/facebook/react/pull/12496))

## 16.3.0 (March 29, 2018)

### React

* Add a new officially supported context API. ([@acdlite](https://github.com/acdlite) in [#11818](https://github.com/facebook/react/pull/11818))
* Add a new `React.createRef()` API as an ergonomic alternative to callback refs. ([@trueadm](https://github.com/trueadm) in [#12162](https://github.com/facebook/react/pull/12162))
* Add a new `React.forwardRef()` API to let components forward their refs to a child. ([@bvaughn](https://github.com/bvaughn) in [#12346](https://github.com/facebook/react/pull/12346))
* Fix a false positive warning in IE11 when using `React.Fragment`. ([@XaveScor](https://github.com/XaveScor) in [#11823](https://github.com/facebook/react/pull/11823))
* Replace `React.unstable_AsyncComponent` with `React.unstable_AsyncMode`. ([@acdlite](https://github.com/acdlite) in [#12117](https://github.com/facebook/react/pull/12117))
* Improve the error message when calling `setState()` on an unmounted component. ([@sophiebits](https://github.com/sophiebits) in [#12347](https://github.com/facebook/react/pull/12347))

### React DOM

* Add a new `getDerivedStateFromProps()` lifecycle and `UNSAFE_` aliases for the legacy lifecycles. ([@bvaughn](https://github.com/bvaughn) in [#12028](https://github.com/facebook/react/pull/12028))
* Add a new `getSnapshotBeforeUpdate()` lifecycle. ([@bvaughn](https://github.com/bvaughn) in [#12404](https://github.com/facebook/react/pull/12404))
* Add a new `<React.StrictMode>` wrapper to help prepare apps for async rendering. ([@bvaughn](https://github.com/bvaughn) in [#12083](https://github.com/facebook/react/pull/12083))
* Add support for `onLoad` and `onError` events on the `<link>` tag. ([@roderickhsiao](https://github.com/roderickhsiao) in [#11825](https://github.com/facebook/react/pull/11825))
* Add support for `noModule` boolean attribute on the `<script>` tag. ([@aweary](https://github.com/aweary) in [#11900](https://github.com/facebook/react/pull/11900))
* Fix minor DOM input bugs in IE and Safari. ([@nhunzaker](https://github.com/nhunzaker) in [#11534](https://github.com/facebook/react/pull/11534))
* Correctly detect Ctrl + Enter in `onKeyPress` in more browsers. ([@nstraub](https://github.com/nstraub) in [#10514](https://github.com/facebook/react/pull/10514))
* Fix containing elements getting focused on SSR markup mismatch. ([@koba04](https://github.com/koba04) in [#11737](https://github.com/facebook/react/pull/11737))
* Fix `value` and `defaultValue` to ignore Symbol values. ([@nhunzaker](https://github.com/nhunzaker) in [#11741](https://github.com/facebook/react/pull/11741))
* Fix refs to class components not getting cleaned up when the attribute is removed. ([@bvaughn](https://github.com/bvaughn) in [#12178](https://github.com/facebook/react/pull/12178))
* Fix an IE/Edge issue when rendering inputs into a different window. ([@M-ZubairAhmed](https://github.com/M-ZubairAhmed) in [#11870](https://github.com/facebook/react/pull/11870))
* Throw with a meaningful message if the component runs after jsdom has been destroyed. ([@gaearon](https://github.com/gaearon) in [#11677](https://github.com/facebook/react/pull/11677))
* Don't crash if there is a global variable called `opera` with a `null` value. [@alisherdavronov](https://github.com/alisherdavronov) in [#11854](https://github.com/facebook/react/pull/11854))
* Don't check for old versions of Opera. ([@skiritsis](https://github.com/skiritsis) in [#11921](https://github.com/facebook/react/pull/11921))
* Deduplicate warning messages about `<option selected>`. ([@watadarkstar](https://github.com/watadarkstar) in [#11821](https://github.com/facebook/react/pull/11821))
* Deduplicate warning messages about invalid callback. ([@yenshih](https://github.com/yenshih) in [#11833](https://github.com/facebook/react/pull/11833))
* Deprecate `ReactDOM.unstable_createPortal()` in favor of `ReactDOM.createPortal()`. ([@prometheansacrifice](https://github.com/prometheansacrifice) in [#11747](https://github.com/facebook/react/pull/11747))
* Don't emit User Timing entries for context types. ([@abhaynikam](https://github.com/abhaynikam) in [#12250](https://github.com/facebook/react/pull/12250))
* Improve the error message when context consumer child isn't a function. ([@raunofreiberg](https://github.com/raunofreiberg) in [#12267](https://github.com/facebook/react/pull/12267))
* Improve the error message when adding a ref to a functional component. ([@skiritsis](https://github.com/skiritsis) in [#11782](https://github.com/facebook/react/pull/11782))

### React DOM Server

* Prevent an infinite loop when attempting to render portals with SSR. ([@gaearon](https://github.com/gaearon) in [#11709](https://github.com/facebook/react/pull/11709))
* Warn if a class doesn't extend `React.Component`. ([@wyze](https://github.com/wyze) in [#11993](https://github.com/facebook/react/pull/11993))
* Fix an issue with `this.state` of different components getting mixed up. ([@sophiebits](https://github.com/sophiebits) in [#12323](https://github.com/facebook/react/pull/12323))
* Provide a better message when component type is undefined. ([@HeroProtagonist](https://github.com/HeroProtagonist) in [#11966](https://github.com/facebook/react/pull/11966))

### React Test Renderer

* Fix handling of fragments in `toTree()`. ([@maciej-ka](https://github.com/maciej-ka) in [#12107](https://github.com/facebook/react/pull/12107) and [@gaearon](https://github.com/gaearon) in [#12154](https://github.com/facebook/react/pull/12154))
* Shallow renderer should assign state to `null` for components that don't set it. ([@jwbay](https://github.com/jwbay) in [#11965](https://github.com/facebook/react/pull/11965))
* Shallow renderer should filter legacy context according to `contextTypes`. ([@koba04](https://github.com/koba04) in [#11922](https://github.com/facebook/react/pull/11922))
* Add an unstable API for testing asynchronous rendering. ([@acdlite](https://github.com/acdlite) in [#12478](https://github.com/facebook/react/pull/12478))

### React Is (New)

* First release of the [new package](https://github.com/facebook/react/tree/main/packages/react-is) that libraries can use to detect different React node types. ([@bvaughn](https://github.com/bvaughn) in [#12199](https://github.com/facebook/react/pull/12199))
* Add `ReactIs.isValidElementType()` to help higher-order components validate their inputs. ([@jamesreggio](https://github.com/jamesreggio) in [#12483](https://github.com/facebook/react/pull/12483))

### React Lifecycles Compat (New)

* First release of the [new package](https://github.com/reactjs/react-lifecycles-compat) to help library developers target multiple versions of React. ([@bvaughn](https://github.com/bvaughn) in [#12105](https://github.com/facebook/react/pull/12105))

### Create Subscription (New)

* First release of the [new package](https://github.com/facebook/react/tree/main/packages/create-subscription) to subscribe to external data sources safely for async rendering. ([@bvaughn](https://github.com/bvaughn) in [#12325](https://github.com/facebook/react/pull/12325))

### React Reconciler (Experimental)

* Expose `react-reconciler/persistent` for building renderers that use persistent data structures. ([@gaearon](https://github.com/gaearon) in [#12156](https://github.com/facebook/react/pull/12156))
* Pass host context to `finalizeInitialChildren()`. ([@jquense](https://github.com/jquense) in [#11970](https://github.com/facebook/react/pull/11970))
* Remove `useSyncScheduling` from the host config. ([@acdlite](https://github.com/acdlite) in [#11771](https://github.com/facebook/react/pull/11771))

### React Call Return (Experimental)

* Fix a crash on updates. ([@rmhartog](https://github.com/rmhartog) in [#11955](https://github.com/facebook/react/pull/11955))

## 16.2.1 (August 1, 2018)

### React DOM Server

* Fix a [potential XSS vulnerability when the attacker controls an attribute name](https://reactjs.org/blog/2018/08/01/react-v-16-4-2.html) (`CVE-2018-6341`). This fix is available in the latest `react-dom@16.4.2`, as well as in previous affected minor versions: `react-dom@16.0.1`, `react-dom@16.1.2`, `react-dom@16.2.1`, and `react-dom@16.3.3`. ([@gaearon](https://github.com/gaearon) in [#13302](https://github.com/facebook/react/pull/13302))

## 16.2.0 (November 28, 2017)

### React

* Add `Fragment` as named export to React. ([@clemmy](https://github.com/clemmy) in [#10783](https://github.com/facebook/react/pull/10783))
* Support experimental Call/Return types in `React.Children` utilities. ([@MatteoVH](https://github.com/MatteoVH) in [#11422](https://github.com/facebook/react/pull/11422))

### React DOM

* Fix radio buttons not getting checked when using multiple lists of radios. ([@landvibe](https://github.com/landvibe) in [#11227](https://github.com/facebook/react/pull/11227))
* Fix radio buttons not receiving the `onChange` event in some cases. ([@jquense](https://github.com/jquense) in [#11028](https://github.com/facebook/react/pull/11028))

### React Test Renderer

* Fix `setState()` callback firing too early when called from `componentWillMount`. ([@accordeiro](https://github.com/accordeiro) in [#11507](https://github.com/facebook/react/pull/11507))

### React Reconciler

* Expose `react-reconciler/reflection` with utilities useful to custom renderers. ([@rivenhk](https://github.com/rivenhk) in [#11683](https://github.com/facebook/react/pull/11683))

### Internal Changes

* Many tests were rewritten against the public API. Big thanks to [everyone who contributed](https://github.com/facebook/react/issues/11299)!

## 16.1.2 (August 1, 2018)

### React DOM Server

* Fix a [potential XSS vulnerability when the attacker controls an attribute name](https://reactjs.org/blog/2018/08/01/react-v-16-4-2.html) (`CVE-2018-6341`). This fix is available in the latest `react-dom@16.4.2`, as well as in previous affected minor versions: `react-dom@16.0.1`, `react-dom@16.1.2`, `react-dom@16.2.1`, and `react-dom@16.3.3`. ([@gaearon](https://github.com/gaearon) in [#13302](https://github.com/facebook/react/pull/13302))

## 16.1.1 (November 13, 2017)

### React

* Improve the warning about undefined component type. ([@selbekk](https://github.com/selbekk) in [#11505](https://github.com/facebook/react/pull/11505))

### React DOM

* Support string values for the `capture` attribute. ([@maxschmeling](https://github.com/maxschmeling) in [#11424](https://github.com/facebook/react/pull/11424))

### React DOM Server

* Don't freeze the `ReactDOMServer` public API. ([@travi](https://github.com/travi) in [#11531](https://github.com/facebook/react/pull/11531))
* Don't emit `autoFocus={false}` attribute on the server. ([@gaearon](https://github.com/gaearon) in [#11543](https://github.com/facebook/react/pull/11543))

### React Reconciler

* Change the hydration API for better Flow typing. ([@sebmarkbage](https://github.com/sebmarkbage) in [#11493](https://github.com/facebook/react/pull/11493))

## 16.1.0 (November 9, 2017)

### Discontinuing Bower Releases

Starting with 16.1.0, we will no longer be publishing new releases on Bower. You can continue using Bower for old releases, or point your Bower configs to the [React UMD builds hosted on unpkg](https://reactjs.org/docs/installation.html#using-a-cdn) that mirror npm releases and will continue to be updated.

### All Packages

* Fix an accidental extra global variable in the UMD builds. ([@gaearon](https://github.com/gaearon) in [#10935](https://github.com/facebook/react/pull/10935))

### React

* Add support for portals in `React.Children` utilities. ([@MatteoVH](https://github.com/MatteoVH) in [#11378](https://github.com/facebook/react/pull/11378))
* Warn when a class has a `render` method but doesn't extend a known base class. ([@sw-yx](https://github.com/sw-yx) in [#11168](https://github.com/facebook/react/pull/11168))
* Improve the warning when accidentally returning an object from constructor. ([@deanbrophy](https://github.com/deanbrophy) in [#11395](https://github.com/facebook/react/pull/11395))

### React DOM

* Allow `on` as a custom attribute for AMP. ([@nuc](https://github.com/nuc) in [#11153](https://github.com/facebook/react/pull/11153))
* Fix `onMouseEnter` and `onMouseLeave` firing on wrong elements. ([@gaearon](https://github.com/gaearon) in [#11164](https://github.com/facebook/react/pull/11164))
* Fix `null` showing up in a warning instead of the component stack. ([@gaearon](https://github.com/gaearon) in [#10915](https://github.com/facebook/react/pull/10915))
* Fix IE11 crash in development mode. ([@leidegre](https://github.com/leidegre) in [#10921](https://github.com/facebook/react/pull/10921))
* Fix `tabIndex` not getting applied to SVG elements. ([@gaearon](https://github.com/gaearon) in [#11034](https://github.com/facebook/react/pull/11034))
* Fix SVG children not getting cleaned up on `dangerouslySetInnerHTML` in IE. ([@OriR](https://github.com/OriR) in [#11108](https://github.com/facebook/react/pull/11108))
* Fix false positive text mismatch warning caused by newline normalization. ([@gaearon](https://github.com/gaearon) in [#11119](https://github.com/facebook/react/pull/11119))
* Fix `form.reset()` to respect `defaultValue` on uncontrolled `<select>`. ([@aweary](https://github.com/aweary) in [#11057](https://github.com/facebook/react/pull/11057))
* Fix `<textarea>` placeholder not rendering on IE11. ([@gaearon](https://github.com/gaearon) in [#11177](https://github.com/facebook/react/pull/11177))
* Fix a crash rendering into shadow root. ([@gaearon](https://github.com/gaearon) in [#11037](https://github.com/facebook/react/pull/11037))
* Fix false positive warning about hydrating mixed case SVG tags. ([@gaearon](https://github.com/gaearon) in [#11174](https://github.com/facebook/react/pull/11174))
* Suppress the new unknown tag warning for `<dialog>` element. ([@gaearon](https://github.com/gaearon) in [#11035](https://github.com/facebook/react/pull/11035))
* Warn when defining a non-existent `componentDidReceiveProps` method. ([@iamtommcc](https://github.com/iamtommcc) in [#11479](https://github.com/facebook/react/pull/11479))
* Warn about function child no more than once. ([@andreysaleba](https://github.com/andreysaleba) in [#11120](https://github.com/facebook/react/pull/11120))
* Warn about nested updates no more than once. ([@anushreesubramani](https://github.com/anushreesubramani) in [#11113](https://github.com/facebook/react/pull/11113))
* Deduplicate other warnings about updates. ([@anushreesubramani](https://github.com/anushreesubramani) in [#11216](https://github.com/facebook/react/pull/11216))
* Include component stack into the warning about `contentEditable` and `children`. ([@Ethan-Arrowood](https://github.com/Ethan-Arrowood) in [#11208](https://github.com/facebook/react/pull/11208))
* Improve the warning about booleans passed to event handlers. ([@NicBonetto](https://github.com/NicBonetto) in [#11308](https://github.com/facebook/react/pull/11308))
* Improve the warning when a multiple `select` gets null `value`. ([@Hendeca](https://github.com/Hendeca) in [#11141](https://github.com/facebook/react/pull/11141))
* Move link in the warning message to avoid redirect. ([@marciovicente](https://github.com/marciovicente) in [#11400](https://github.com/facebook/react/pull/11400))
* Add a way to suppress the React DevTools installation prompt. ([@gaearon](https://github.com/gaearon) in [#11448](https://github.com/facebook/react/pull/11448))
* Remove unused code. ([@gaearon](https://github.com/gaearon) in [#10802](https://github.com/facebook/react/pull/10802), [#10803](https://github.com/facebook/react/pull/10803))

### React DOM Server

* Add a new `suppressHydrationWarning` attribute for intentional client/server text mismatches. ([@sebmarkbage](https://github.com/sebmarkbage) in [#11126](https://github.com/facebook/react/pull/11126))
* Fix markup generation when components return strings. ([@gaearon](https://github.com/gaearon) in [#11109](https://github.com/facebook/react/pull/11109))
* Fix obscure error message when passing an invalid style value. ([@iamdustan](https://github.com/iamdustan) in [#11173](https://github.com/facebook/react/pull/11173))
* Include the `autoFocus` attribute into SSR markup. ([@gaearon](https://github.com/gaearon) in [#11192](https://github.com/facebook/react/pull/11192))
* Include the component stack into more warnings. ([@gaearon](https://github.com/gaearon) in [#11284](https://github.com/facebook/react/pull/11284))

### React Test Renderer and Test Utils

* Fix multiple `setState()` calls in `componentWillMount()` in shallow renderer. ([@Hypnosphi](https://github.com/Hypnosphi) in [#11167](https://github.com/facebook/react/pull/11167))
* Fix shallow renderer to ignore `shouldComponentUpdate()` after `forceUpdate()`. ([@d4rky-pl](https://github.com/d4rky-pl) in [#11239](https://github.com/facebook/react/pull/11239) and [#11439](https://github.com/facebook/react/pull/11439))
* Handle `forceUpdate()` and `React.PureComponent` correctly. ([@koba04](https://github.com/koba04) in [#11440](https://github.com/facebook/react/pull/11440))
* Add back support for running in production mode. ([@gaearon](https://github.com/gaearon) in [#11112](https://github.com/facebook/react/pull/11112))
* Add a missing `package.json` dependency. ([@gaearon](https://github.com/gaearon) in [#11340](https://github.com/facebook/react/pull/11340))

### React ART

* Add a missing `package.json` dependency. ([@gaearon](https://github.com/gaearon) in [#11341](https://github.com/facebook/react/pull/11341))
* Expose `react-art/Circle`, `react-art/Rectangle`, and `react-art/Wedge`. ([@gaearon](https://github.com/gaearon) in [#11343](https://github.com/facebook/react/pull/11343))

### React Reconciler (Experimental)

* First release of the [new experimental package](https://github.com/facebook/react/blob/main/packages/react-reconciler/README.md) for creating custom renderers. ([@iamdustan](https://github.com/iamdustan) in [#10758](https://github.com/facebook/react/pull/10758))
* Add support for React DevTools. ([@gaearon](https://github.com/gaearon) in [#11463](https://github.com/facebook/react/pull/11463))

### React Call Return (Experimental)

* First release of the [new experimental package](https://github.com/facebook/react/tree/main/packages/react-call-return) for parent-child communication. ([@gaearon](https://github.com/gaearon) in [#11364](https://github.com/facebook/react/pull/11364))

## 16.0.1 (August 1, 2018)

### React DOM Server

* Fix a [potential XSS vulnerability when the attacker controls an attribute name](https://reactjs.org/blog/2018/08/01/react-v-16-4-2.html) (`CVE-2018-6341`). This fix is available in the latest `react-dom@16.4.2`, as well as in previous affected minor versions: `react-dom@16.0.1`, `react-dom@16.1.2`, `react-dom@16.2.1`, and `react-dom@16.3.3`. ([@gaearon](https://github.com/gaearon) in [#13302](https://github.com/facebook/react/pull/13302))

## 16.0.0 (September 26, 2017)

### New JS Environment Requirements

 * React 16 depends on the collection types [Map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) and [Set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set), as well as [requestAnimationFrame](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame). If you support older browsers and devices which may not yet provide these natively (e.g. <IE11), [you may want to include a polyfill](https://gist.github.com/gaearon/9a4d54653ae9c50af6c54b4e0e56b583).

### New Features
* Components can now return arrays and strings from `render`. (Docs coming soon!)
* Improved error handling with introduction of "error boundaries". [Error boundaries](https://reactjs.org/blog/2017/07/26/error-handling-in-react-16.html) are React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI instead of the component tree that crashed.
* First-class support for declaratively rendering a subtree into another DOM node with `ReactDOM.createPortal()`. (Docs coming soon!)
* Streaming mode for server side rendering is enabled with `ReactDOMServer.renderToNodeStream()` and `ReactDOMServer.renderToStaticNodeStream()`. ([@aickin](https://github.com/aickin) in [#10425](https://github.com/facebook/react/pull/10425), [#10044](https://github.com/facebook/react/pull/10044), [#10039](https://github.com/facebook/react/pull/10039), [#10024](https://github.com/facebook/react/pull/10024), [#9264](https://github.com/facebook/react/pull/9264), and others.)
* [React DOM now allows passing non-standard attributes](https://reactjs.org/blog/2017/09/08/dom-attributes-in-react-16.html). ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)

### Breaking Changes
- There are several changes to the behavior of scheduling and lifecycle methods:
  * `ReactDOM.render()` and `ReactDOM.unstable_renderIntoContainer()` now return `null` if called from inside a lifecycle method.
    * To work around this, you can either use [the new portal API](https://github.com/facebook/react/issues/10309#issuecomment-318433235) or [refs](https://github.com/facebook/react/issues/10309#issuecomment-318434635).
  * Minor changes to `setState` behavior:
    * Calling `setState` with null no longer triggers an update. This allows you to decide in an updater function if you want to re-render.
    * Calling `setState` directly in render always causes an update. This was not previously the case. Regardless, you should not be calling `setState` from render.
    * `setState` callback (second argument) now fires immediately after `componentDidMount` / `componentDidUpdate` instead of after all components have rendered.
  * When replacing `<A />` with `<B />`,  `B.componentWillMount` now always happens before  `A.componentWillUnmount`. Previously, `A.componentWillUnmount` could fire first in some cases.
  * Previously, changing the `ref` to a component would always detach the ref before that component's render is called. Now, we change the `ref` later, when applying the changes to the DOM.
  * It is not safe to re-render into a container that was modified by something other than React. This worked previously in some cases but was never supported. We now emit a warning in this case. Instead you should clean up your component trees using `ReactDOM.unmountComponentAtNode`. [See this example.](https://github.com/facebook/react/issues/10294#issuecomment-318820987)
  * `componentDidUpdate` lifecycle no longer receives `prevContext` param. ([@bvaughn](https://github.com/bvaughn) in [#8631](https://github.com/facebook/react/pull/8631))
  * Non-unique keys may now cause children to be duplicated and/or omitted. Using non-unique keys is not (and has never been) supported, but previously it was a hard error.
  * Shallow renderer no longer calls `componentDidUpdate()` because DOM refs are not available. This also makes it consistent with `componentDidMount()` (which does not get called in previous versions either).
  * Shallow renderer does not implement `unstable_batchedUpdates()` anymore.
  * `ReactDOM.unstable_batchedUpdates` now only takes one extra argument after the callback.
- The names and paths to the single-file browser builds have changed to emphasize the difference between development and production builds. For example:
  - `react/dist/react.js` → `react/umd/react.development.js`
  - `react/dist/react.min.js` → `react/umd/react.production.min.js`
  - `react-dom/dist/react-dom.js` → `react-dom/umd/react-dom.development.js`
  - `react-dom/dist/react-dom.min.js` → `react-dom/umd/react-dom.production.min.js`
* The server renderer has been completely rewritten, with some improvements:
  * Server rendering does not use markup validation anymore, and instead tries its best to attach to existing DOM, warning about inconsistencies. It also doesn't use comments for empty components and data-reactid attributes on each node anymore.
  * Hydrating a server rendered container now has an explicit API. Use `ReactDOM.hydrate` instead of `ReactDOM.render` if you're reviving server rendered HTML. Keep using `ReactDOM.render` if you're just doing client-side rendering.
* When "unknown" props are passed to DOM components, for valid values, React will now render them in the DOM. [See this post for more details.](https://reactjs.org/blog/2017/09/08/dom-attributes-in-react-16.html) ([@nhunzaker](https://github.com/nhunzaker) in [#10385](https://github.com/facebook/react/pull/10385), [10564](https://github.com/facebook/react/pull/10564), [#10495](https://github.com/facebook/react/pull/10495) and others)
* Errors in the render and lifecycle methods now unmount the component tree by default. To prevent this, add [error boundaries](https://reactjs.org/blog/2017/07/26/error-handling-in-react-16.html) to the appropriate places in the UI.

### Removed Deprecations

- There is no `react-with-addons.js` build anymore. All compatible addons are published separately on npm, and have single-file browser versions if you need them.
- The deprecations introduced in 15.x have been removed from the core package. `React.createClass` is now available as create-react-class, `React.PropTypes` as prop-types, `React.DOM` as react-dom-factories, react-addons-test-utils as react-dom/test-utils, and shallow renderer as react-test-renderer/shallow. See [15.5.0](https://reactjs.org/blog/2017/04/07/react-v15.5.0.html) and [15.6.0](https://reactjs.org/blog/2017/06/13/react-v15.6.0.html) blog posts for instructions on migrating code and automated codemods.

## 15.7.0 (October 14, 2020)

### React

* Backport support for the [new JSX transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) to 15.x. ([@lunaruan](https://github.com/lunaruan) in [#18299](https://github.com/facebook/react/pull/18299) and [@gaearon](https://github.com/gaearon) in [#20024](https://github.com/facebook/react/pull/20024))

## 15.6.2 (September 25, 2017)

### All Packages
* Switch from BSD + Patents to MIT license

### React DOM

* Fix a bug where modifying `document.documentMode` would trigger IE detection in other browsers, breaking change events. ([@aweary](https://github.com/aweary) in [#10032](https://github.com/facebook/react/pull/10032))
* CSS Columns are treated as unitless numbers. ([@aweary](https://github.com/aweary) in [#10115](https://github.com/facebook/react/pull/10115))
* Fix bug in QtWebKit when wrapping synthetic events in proxies. ([@walrusfruitcake](https://github.com/walrusfruitcake) in [#10115](https://github.com/facebook/react/pull/10011))
* Prevent event handlers from receiving extra argument in development. ([@aweary](https://github.com/aweary) in [#10115](https://github.com/facebook/react/pull/8363))
* Fix cases where `onChange` would not fire with `defaultChecked` on radio inputs. ([@jquense](https://github.com/jquense) in [#10156](https://github.com/facebook/react/pull/10156))
* Add support for `controlList` attribute to allowed DOM properties ([@nhunzaker](https://github.com/nhunzaker) in [#9940](https://github.com/facebook/react/pull/9940))
* Fix a bug where creating an element with a ref in a constructor did not throw an error in development. ([@iansu](https://github.com/iansu) in [#10025](https://github.com/facebook/react/pull/10025))

## 15.6.1 (June 14, 2017)

### React DOM

* Fix a crash on iOS Safari. ([@jquense](https://github.com/jquense) in [#9960](https://github.com/facebook/react/pull/9960))
* Don't add `px` to custom CSS property values. ([@TrySound](https://github.com/TrySound) in [#9966](https://github.com/facebook/react/pull/9966))

## 15.6.0 (June 13, 2017)

### React

* Downgrade deprecation warnings to use `console.warn` instead of `console.error`. ([@flarnie](https://github.com/flarnie) in [#9753](https://github.com/facebook/react/pull/9753))
* Add a deprecation warning for `React.createClass`. Points users to `create-react-class` instead. ([@flarnie](https://github.com/flarnie) in [#9771](https://github.com/facebook/react/pull/9771))
* Add deprecation warnings and separate module for `React.DOM` factory helpers. ([@nhunzaker](https://github.com/nhunzaker) in [#8356](https://github.com/facebook/react/pull/8356))
* Warn for deprecation of `React.createMixin` helper, which was never used. ([@aweary](https://github.com/aweary) in [#8853](https://github.com/facebook/react/pull/8853))

### React DOM

* Add support for CSS variables in `style` attribute. ([@aweary](https://github.com/aweary) in [#9302](https://github.com/facebook/react/pull/9302))
* Add support for CSS Grid style properties. ([@ericsakmar](https://github.com/ericsakmar) in [#9185](https://github.com/facebook/react/pull/9185))
* Fix bug where inputs mutated value on type conversion. ([@nhunzaker](https://github.com/mhunzaker) in [#9806](https://github.com/facebook/react/pull/9806))
* Fix issues with `onChange` not firing properly for some inputs. ([@jquense](https://github.com/jquense) in [#8575](https://github.com/facebook/react/pull/8575))
* Fix bug where controlled number input mistakenly allowed period. ([@nhunzaker](https://github.com/nhunzaker) in [#9584](https://github.com/facebook/react/pull/9584))
* Fix bug where performance entries were being cleared. ([@chrisui](https://github.com/chrisui) in [#9451](https://github.com/facebook/react/pull/9451))

### React Addons

* Fix AMD support for addons depending on `react`. ([@flarnie](https://github.com/flarnie) in [#9919](https://github.com/facebook/react/issues/9919))
* Fix `isMounted()` to return `true` in `componentWillUnmount`. ([@mridgway](https://github.com/mridgway) in [#9638](https://github.com/facebook/react/issues/9638))
* Fix `react-addons-update` to not depend on native `Object.assign`. ([@gaearon](https://github.com/gaearon) in [#9937](https://github.com/facebook/react/pull/9937))
* Remove broken Google Closure Compiler annotation from `create-react-class`. ([@gaearon](https://github.com/gaearon) in [#9933](https://github.com/facebook/react/pull/9933))
* Remove unnecessary dependency from `react-linked-input`. ([@gaearon](https://github.com/gaearon) in [#9766](https://github.com/facebook/react/pull/9766))
* Point `react-addons-(css-)transition-group` to the new package. ([@gaearon](https://github.com/gaearon) in [#9937](https://github.com/facebook/react/pull/9937))

## 15.5.4 (April 11, 2017)

### React Addons
* **Critical Bugfix:** Update the version of `prop-types` to fix critical bug.  ([@gaearon](https://github.com/gaearon) in [545c87f](https://github.com/facebook/react/commit/545c87fdc348f82eb0c3830bef715ed180785390))
* Fix `react-addons-create-fragment` package to include `loose-envify` transform for Browserify users. ([@mridgway](https://github.com/mridgway) in [#9642](https://github.com/facebook/react/pull/9642))

### React Test Renderer
* Fix compatibility with Enzyme by exposing `batchedUpdates` on shallow renderer. ([@gaearon](https://github.com/gaearon) in [9382](https://github.com/facebook/react/commit/69933e25c37cf5453a9ef132177241203ee8d2fd))

## 15.5.3 (April 7, 2017)

**Note: this release has a critical issue and was deprecated. Please update to 15.5.4 or higher.**

### React Addons
* Fix `react-addons-create-fragment` package to export correct thing. ([@gaearon](https://github.com/gaearon) in [#9385](https://github.com/facebook/react/pull/9383))
* Fix `create-react-class` package to include `loose-envify` transform for Browserify users. ([@mridgway](https://github.com/mridgway) in [#9642](https://github.com/facebook/react/pull/9642))

## 15.5.2 (April 7, 2017)

**Note: this release has a critical issue and was deprecated. Please update to 15.5.4 or higher.**

### React Addons
* Fix the production single-file builds to not include the development code. ([@gaearon](https://github.com/gaearon) in [#9385](https://github.com/facebook/react/pull/9383))
* Apply better minification to production single-file builds. ([@gaearon](https://github.com/gaearon) in [#9385](https://github.com/facebook/react/pull/9383))
* Add missing and remove unnecessary dependencies to packages. ([@gaearon](https://github.com/gaearon) in [#9385](https://github.com/facebook/react/pull/9383))

## 15.5.1 (April 7, 2017)

**Note: this release has a critical issue and was deprecated. Please update to 15.5.4 or higher.**

### React
* Fix erroneous PropTypes access warning. ([@acdlite](https://github.com/acdlite) in ([ec97ebb](https://github.com/facebook/react/commit/ec97ebbe7f15b58ae2f1323df39d06f119873344))

## 15.5.0 (April 7, 2017)

**Note: this release has a critical issue and was deprecated. Please update to 15.5.4 or higher.**

### React
* <s>Added a deprecation warning for `React.createClass`. Points users to create-react-class instead. ([@acdlite](https://github.com/acdlite) in [#d9a4fa4](https://github.com/facebook/react/commit/d9a4fa4f51c6da895e1655f32255cf72c0fe620e))</s>
* Added a deprecation warning for `React.PropTypes`. Points users to prop-types instead. ([@acdlite](https://github.com/acdlite) in [#043845c](https://github.com/facebook/react/commit/043845ce75ea0812286bbbd9d34994bb7e01eb28))
* Fixed an issue when using `ReactDOM` together with `ReactDOMServer`. ([@wacii](https://github.com/wacii) in [#9005](https://github.com/facebook/react/pull/9005))
* Fixed issue with Closure Compiler. ([@anmonteiro](https://github.com/anmonteiro) in [#8895](https://github.com/facebook/react/pull/8895))
* Another fix for Closure Compiler. ([@Shastel](https://github.com/Shastel) in [#8882](https://github.com/facebook/react/pull/8882))
* Added component stack info to invalid element type warning. ([@n3tr](https://github.com/n3tr) in [#8495](https://github.com/facebook/react/pull/8495))

### React DOM
* Fixed Chrome bug when backspacing in number inputs. ([@nhunzaker](https://github.com/nhunzaker) in [#7359](https://github.com/facebook/react/pull/7359))
* Added `react-dom/test-utils`, which exports the React Test Utils. ([@bvaughn](https://github.com/bvaughn))

### React Test Renderer
* Fixed bug where `componentWillUnmount` was not called for children. ([@gre](https://github.com/gre) in [#8512](https://github.com/facebook/react/pull/8512))
* Added `react-test-renderer/shallow`, which exports the shallow renderer. ([@bvaughn](https://github.com/bvaughn))

### React Addons
* Last release for addons; they will no longer be actively maintained.
* Removed `peerDependencies` so that addons continue to work indefinitely. ([@acdlite](https://github.com/acdlite) and [@bvaughn](https://github.com/bvaughn) in [8a06cd7](https://github.com/facebook/react/commit/8a06cd7a786822fce229197cac8125a551e8abfa) and [67a8db3](https://github.com/facebook/react/commit/67a8db3650d724a51e70be130e9008806402678a))
* Updated to remove references to `React.createClass` and `React.PropTypes` ([@acdlite](https://github.com/acdlite) in [12a96b9](https://github.com/facebook/react/commit/12a96b94823d6b6de6b1ac13bd576864abd50175))
* `react-addons-test-utils` is deprecated. Use `react-dom/test-utils` and `react-test-renderer/shallow` instead. ([@bvaughn](https://github.com/bvaughn))

## 15.4.2 (January 6, 2017)

### React
* Fixed build issues with the Brunch bundler. ([@gaearon](https://github.com/gaearon) in [#8686](https://github.com/facebook/react/pull/8686))
* Improved error messages for invalid element types. ([@sophiebits](https://github.com/sophiebits) in [#8612](https://github.com/facebook/react/pull/8612))
* Removed a warning about `getInitialState` when `this.state` is set. ([@bvaughn](https://github.com/bvaughn) in [#8594](https://github.com/facebook/react/pull/8594))
* Removed some dead code. ([@diegomura](https://github.com/diegomura) in [#8050](https://github.com/facebook/react/pull/8050), [@dfrownfelter](https://github.com/dfrownfelter) in [#8597](https://github.com/facebook/react/pull/8597))

### React DOM
* Fixed a decimal point issue on uncontrolled number inputs. ([@nhunzaker](https://github.com/nhunzaker) in [#7750](https://github.com/facebook/react/pull/7750))
* Fixed rendering of textarea placeholder in IE11. ([@aweary](https://github.com/aweary) in [#8020](https://github.com/facebook/react/pull/8020))
* Worked around a script engine bug in IE9. ([@eoin](https://github.com/eoin) in [#8018](https://github.com/facebook/react/pull/8018))

### React Addons
* Fixed build issues in RequireJS and SystemJS environments. ([@gaearon](https://github.com/gaearon) in [#8686](https://github.com/facebook/react/pull/8686))
* Added missing package dependencies. ([@kweiberth](https://github.com/kweiberth) in [#8467](https://github.com/facebook/react/pull/8467))

## 15.4.1 (November 22, 2016)

### React
* Restructure variable assignment to work around a Rollup bug ([@gaearon](https://github.com/gaearon) in [#8384](https://github.com/facebook/react/pull/8384))

### React DOM
* Fixed event handling on disabled button elements ([@sophiebits](https://github.com/sophiebits) in [#8387](https://github.com/facebook/react/pull/8387))
* Fixed compatibility of browser build with AMD environments ([@zpao](https://github.com/zpao) in [#8374](https://github.com/facebook/react/pull/8374))

## 15.4.0 (November 16, 2016)

### React
* React package and browser build no longer "secretly" includes React DOM. ([@sebmarkbage](https://github.com/sebmarkbage) in [#7164](https://github.com/facebook/react/pull/7164) and [#7168](https://github.com/facebook/react/pull/7168))
* Required PropTypes now fail with specific messages for null and undefined. ([@chenglou](https://github.com/chenglou) in [#7291](https://github.com/facebook/react/pull/7291))
* Improved development performance by freezing children instead of copying. ([@keyanzhang](https://github.com/keyanzhang) in [#7455](https://github.com/facebook/react/pull/7455))

### React DOM
* Fixed occasional test failures when React DOM is used together with shallow renderer. ([@goatslacker](https://github.com/goatslacker) in [#8097](https://github.com/facebook/react/pull/8097))
* Added a warning for invalid `aria-` attributes. ([@jessebeach](https://github.com/jessebeach) in [#7744](https://github.com/facebook/react/pull/7744))
* Added a warning for using `autofocus` rather than `autoFocus`. ([@hkal](https://github.com/hkal) in [#7694](https://github.com/facebook/react/pull/7694))
* Removed an unnecessary warning about polyfilling `String.prototype.split`. ([@nhunzaker](https://github.com/nhunzaker) in [#7629](https://github.com/facebook/react/pull/7629))
* Clarified the warning about not calling PropTypes manually. ([@jedwards1211](https://github.com/jedwards1211) in [#7777](https://github.com/facebook/react/pull/7777))
* The unstable `batchedUpdates` API now passes the wrapped function's return value through. ([@bgnorlov](https://github.com/bgnorlov) in [#7444](https://github.com/facebook/react/pull/7444))
* Fixed a bug with updating text in IE 8. ([@mnpenner](https://github.com/mnpenner) in [#7832](https://github.com/facebook/react/pull/7832))

### React Perf
* When ReactPerf is started, you can now view the relative time spent in components as a chart in Chrome Timeline. ([@gaearon](https://github.com/gaearon) in [#7549](https://github.com/facebook/react/pull/7549))

### React Test Utils
* If you call `Simulate.click()` on a `<input disabled onClick={foo} />` then `foo` will get called whereas it didn't before. ([@nhunzaker](https://github.com/nhunzaker) in [#7642](https://github.com/facebook/react/pull/7642))

### React Test Renderer
* Due to packaging changes, it no longer crashes when imported together with React DOM in the same file. ([@sebmarkbage](https://github.com/sebmarkbage) in [#7164](https://github.com/facebook/react/pull/7164) and [#7168](https://github.com/facebook/react/pull/7168))
* `ReactTestRenderer.create()` now accepts `{createNodeMock: element => mock}` as an optional argument so you can mock refs with snapshot testing. ([@Aweary](https://github.com/Aweary) in [#7649](https://github.com/facebook/react/pull/7649), [#8261](https://github.com/facebook/react/pull/8261))


## 15.3.2 (September 19, 2016)

### React
- Remove plain object warning from React.createElement & React.cloneElement. ([@spudly](https://github.com/spudly) in [#7724](https://github.com/facebook/react/pull/7724))

### React DOM
- Add `playsInline` to supported HTML attributes. ([@reaperhulk](https://github.com/reaperhulk) in [#7519](https://github.com/facebook/react/pull/7519))
- Add `as` to supported HTML attributes. ([@kevinslin](https://github.com/kevinslin) in [#7582](https://github.com/facebook/react/pull/7582))
- Improve DOM nesting validation warning about whitespace. ([@sophiebits](https://github.com/sophiebits) in [#7515](https://github.com/facebook/react/pull/7515))
- Avoid "Member not found" exception in IE10 when calling `preventDefault()` in Synthetic Events. ([@g-palmer](https://github.com/g-palmer) in [#7411](https://github.com/facebook/react/pull/7411))
- Fix memory leak in `onSelect` implementation. ([@AgtLucas](https://github.com/AgtLucas) in [#7533](https://github.com/facebook/react/pull/7533))
- Improve robustness of `document.documentMode` checks to handle Google Tag Manager. ([@SchleyB](https://github.com/SchleyB) in [#7594](https://github.com/facebook/react/pull/7594))
- Add more cases to controlled inputs warning. ([@marcin-mazurek](https://github.com/marcin-mazurek) in [#7544](https://github.com/facebook/react/pull/7544))
- Handle case of popup blockers overriding `document.createEvent`. ([@Andarist](https://github.com/Andarist) in [#7621](https://github.com/facebook/react/pull/7621))
- Fix issue with `dangerouslySetInnerHTML` and SVG in Internet Explorer. ([@zpao](https://github.com/zpao) in [#7618](https://github.com/facebook/react/pull/7618))
- Improve handling of Japanese IME on Internet Explorer. ([@msmania](https://github.com/msmania) in [#7107](https://github.com/facebook/react/pull/7107))

### React Test Renderer
- Support error boundaries. ([@millermedeiros](https://github.com/millermedeiros) in [#7558](https://github.com/facebook/react/pull/7558), [#7569](https://github.com/facebook/react/pull/7569), [#7619](https://github.com/facebook/react/pull/7619))
- Skip null ref warning. ([@Aweary](https://github.com/Aweary) in [#7658](https://github.com/facebook/react/pull/7658))

### React Perf Add-on
- Ensure lifecycle timers are stopped on errors. ([@gaearon](https://github.com/gaearon) in [#7548](https://github.com/facebook/react/pull/7548))


## 15.3.1 (August 19, 2016)

### React

- Improve performance of development builds in various ways. ([@gaearon](https://github.com/gaearon) in [#7461](https://github.com/facebook/react/pull/7461), [#7463](https://github.com/facebook/react/pull/7463), [#7483](https://github.com/facebook/react/pull/7483), [#7488](https://github.com/facebook/react/pull/7488), [#7491](https://github.com/facebook/react/pull/7491), [#7510](https://github.com/facebook/react/pull/7510))
- Cleanup internal hooks to improve performance of development builds. ([@gaearon](https://github.com/gaearon) in [#7464](https://github.com/facebook/react/pull/7464), [#7472](https://github.com/facebook/react/pull/7472), [#7481](https://github.com/facebook/react/pull/7481), [#7496](https://github.com/facebook/react/pull/7496))
- Upgrade fbjs to pick up another performance improvement from [@gaearon](https://github.com/gaearon) for development builds. ([@zpao](https://github.com/zpao) in [#7532](https://github.com/facebook/react/pull/7532))
- Improve startup time of React in Node. ([@zertosh](https://github.com/zertosh) in [#7493](https://github.com/facebook/react/pull/7493))
- Improve error message of `React.Children.only`. ([@sophiebits](https://github.com/sophiebits) in [#7514](https://github.com/facebook/react/pull/7514))

### React DOM
- Avoid `<input>` validation warning from browsers when changing `type`. ([@nhunzaker](https://github.com/nhunzaker) in [#7333](https://github.com/facebook/react/pull/7333))
- Avoid "Member not found" exception in IE10 when calling `stopPropagation()` in Synthetic Events. ([@nhunzaker](https://github.com/nhunzaker) in [#7343](https://github.com/facebook/react/pull/7343))
- Fix issue resulting in inability to update some `<input>` elements in mobile browsers. ([@keyanzhang](https://github.com/keyanzhang) in [#7397](https://github.com/facebook/react/pull/7397))
- Fix memory leak in server rendering. ([@keyanzhang](https://github.com/keyanzhang) in [#7410](https://github.com/facebook/react/pull/7410))
- Fix issue resulting in `<input type="range">` values not updating when changing `min` or `max`. ([@troydemonbreun](https://github.com/troydemonbreun) in [#7486](https://github.com/facebook/react/pull/7486))
- Add new warning for rare case of attempting to unmount a container owned by a different copy of React. ([@ventuno](https://github.com/ventuno) in [#7456](https://github.com/facebook/react/pull/7456))

### React Test Renderer
- Fix ReactTestInstance::toJSON() with empty top-level components. ([@Morhaus](https://github.com/Morhaus) in [#7523](https://github.com/facebook/react/pull/7523))

### React Native Renderer
- Change `trackedTouchCount` invariant into a console.error for better reliability. ([@yungsters](https://github.com/yungsters) in [#7400](https://github.com/facebook/react/pull/7400))


## 15.3.0 (July 29, 2016)

### React
- Add `React.PureComponent` - a new base class to extend, replacing `react-addons-pure-render-mixin` now that mixins don't work with ES2015 classes. ([@sophiebits](https://github.com/sophiebits) in [#7195](https://github.com/facebook/react/pull/7195))
- Add new warning when modifying `this.props.children`. ([@jimfb](https://github.com/jimfb) in [#7001](https://github.com/facebook/react/pull/7001))
- Fixed issue with ref resolution order. ([@gaearon](https://github.com/gaearon) in [#7101](https://github.com/facebook/react/pull/7101))
- Warn when mixin is undefined. ([@swaroopsm](https://github.com/swaroopsm) in [#6158](https://github.com/facebook/react/pull/6158))
- Downgrade "unexpected batch number" invariant to a warning. ([@sophiebits](https://github.com/sophiebits) in [#7133](https://github.com/facebook/react/pull/7133))
- Validate arguments to `oneOf` and `oneOfType` PropTypes sooner. ([@troydemonbreun](https://github.com/troydemonbreun) in [#6316](https://github.com/facebook/react/pull/6316))
- Warn when calling PropTypes directly. ([@Aweary](https://github.com/Aweary) in [#7132](https://github.com/facebook/react/pull/7132), [#7194](https://github.com/facebook/react/pull/7194))
- Improve warning when using Maps as children. ([@keyanzhang](https://github.com/keyanzhang) in [#7260](https://github.com/facebook/react/pull/7260))
- Add additional type information to the `PropTypes.element` warning. ([@alexzherdev](https://github.com/alexzherdev) in [#7319](https://github.com/facebook/react/pull/7319))
- Improve component identification in no-op `setState` warning. ([@keyanzhang](https://github.com/keyanzhang) in [#7326](https://github.com/facebook/react/pull/7326))

### React DOM
- Fix issue with nested server rendering. ([@Aweary](https://github.com/Aweary) in [#7033](https://github.com/facebook/react/pull/7033))
- Add `xmlns`, `xmlnsXlink` to supported SVG attributes. ([@salzhrani](https://github.com/salzhrani) in [#6471](https://github.com/facebook/react/pull/6471))
- Add `referrerPolicy` to supported HTML attributes. ([@Aweary](https://github.com/Aweary) in [#7274](https://github.com/facebook/react/pull/7274))
- Fix issue resulting in `<input type="range">` initial value being rounded. ([@troydemonbreun](https://github.com/troydemonbreun) in [#7251](https://github.com/facebook/react/pull/7251))

### React Test Renderer
- Initial public release of package allowing more focused testing. Install with `npm install react-test-renderer`. ([@sophiebits](https://github.com/sophiebits) in [#6944](https://github.com/facebook/react/pull/6944), [#7258](https://github.com/facebook/react/pull/7258), [@iamdustan](https://github.com/iamdustan) in [#7362](https://github.com/facebook/react/pull/7362))

### React Perf Add-on
- Fix issue resulting in excessive warnings when encountering an internal measurement error. ([@sassanh](https://github.com/sassanh) in [#7299](https://github.com/facebook/react/pull/7299))

### React TestUtils Add-on
- Implement `type` property on for events created via `TestUtils.Simulate.*`. ([@yaycmyk](https://github.com/yaycmyk) in [#6154](https://github.com/facebook/react/pull/6154))
- Fix crash when running TestUtils with the production build of React. ([@gaearon](https://github.com/gaearon) in [#7246](https://github.com/facebook/react/pull/7246))


## 15.2.1 (July 8, 2016)

### React
- Fix errant warning about missing React element. ([@gaearon](https://github.com/gaearon) in [#7193](https://github.com/facebook/react/pull/7193))
- Better removal of dev-only code, leading to a small reduction in the minified production bundle size. ([@gaearon](https://github.com/gaearon) in [#7188](https://github.com/facebook/react/pull/7188), [#7189](https://github.com/facebook/react/pull/7189))

### React DOM
- Add stack trace to null input value warning. ([@jimfb](https://github.com/jimfb) in [#7040](https://github.com/facebook/react/pull/7040))
- Fix webcomponents example. ([@jalexanderfox](https://github.com/jalexanderfox) in [#7057](https://github.com/facebook/react/pull/7057))
- Fix `unstable_renderSubtreeIntoContainer` so that context properly updates when linked to state. ([@gaearon](https://github.com/gaearon) in [#7125](https://github.com/facebook/react/pull/7125))
- Improve invariant wording for void elements. ([@starkch](https://github.com/starkch) in [#7066](https://github.com/facebook/react/pull/7066))
- Ensure no errors are thrown due to event handlers in server rendering. ([@rricard](https://github.com/rricard) in [#7127](https://github.com/facebook/react/pull/7127))
- Fix regression resulting in `value`-less submit and reset inputs removing the browser-default text. ([@zpao](https://github.com/zpao) in [#7197](https://github.com/facebook/react/pull/7197))
- Fix regression resulting in empty `name` attribute being added to inputs when not provided. ([@okonet](https://github.com/okonet) in [#7199](https://github.com/facebook/react/pull/7199))
- Fix issue with nested server rendering. ([@Aweary](https://github.com/Aweary) in [#7033](https://github.com/facebook/react/pull/7033))

### React Perf Add-on
- Make `ReactPerf.start()` work properly during lifecycle methods. ([@gaearon](https://github.com/gaearon) in [#7208](https://github.com/facebook/react/pull/7208)).

### React CSSTransitionGroup Add-on
- Fix issue resulting in spurious unknown property warnings. ([@batusai513](https://github.com/batusai513) in [#7165](https://github.com/facebook/react/pull/7165))

### React Native Renderer
- Improve error handling in cross-platform touch event handling. ([@yungsters](https://github.com/yungsters) in [#7143](https://github.com/facebook/react/pull/7143))


## 15.2.0 (July 1, 2016)

### React
- Add error codes to production invariants, with links to the view the full error text. ([@keyanzhang](https://github.com/keyanzhang) in [#6948](https://github.com/facebook/react/pull/6948))
- Include component stack information in PropType validation warnings. ([@troydemonbreun](https://github.com/troydemonbreun) in [#6398](https://github.com/facebook/react/pull/6398), [@sophiebits](https://github.com/sophiebits) in [#6771](https://github.com/facebook/react/pull/6771))
- Include component stack information in key warnings. ([@keyanzhang](https://github.com/keyanzhang) in [#6799](https://github.com/facebook/react/pull/6799))
- Stop validating props at mount time, only validate at element creation. ([@keyanzhang](https://github.com/keyanzhang) in [#6824](https://github.com/facebook/react/pull/6824))
- New invariant providing actionable error in missing instance case. ([@yungsters](https://github.com/yungsters) in [#6990](https://github.com/facebook/react/pull/6990))
- Add `React.PropTypes.symbol` to support ES2015 Symbols as props. ([@puradox](https://github.com/puradox) in [#6377](https://github.com/facebook/react/pull/6377))
- Fix incorrect coercion of ref or key that are undefined in development ([@gaearon](https://github.com/gaearon) in [#6880](https://github.com/facebook/react/pull/6880))
- Fix a false positive when passing other element’s props to cloneElement ([@ericmatthys](https://github.com/ericmatthys) in [#6268](https://github.com/facebook/react/pull/6268))
- Warn if you attempt to define `childContextTypes` on a functional component ([@Aweary](https://github.com/Aweary) in [#6933](https://github.com/facebook/react/pull/6933))

### React DOM
- Add warning for unknown properties on DOM elements. ([@jimfb](https://github.com/jimfb) in [#6800](https://github.com/facebook/react/pull/6800), [@gm758](https://github.com/gm758) in [#7152](https://github.com/facebook/react/pull/7152))
- Properly remove attributes from custom elements. ([@grassator](https://github.com/grassator) in [#6748](https://github.com/facebook/react/pull/6748))
- Fix invalid unicode escape in attribute name regular expression. ([@nbjahan](https://github.com/nbjahan) in [#6772](https://github.com/facebook/react/pull/6772))
- Add `onLoad` handling to `<link>` element. ([@roderickhsiao](https://github.com/roderickhsiao) in [#6815](https://github.com/facebook/react/pull/6815))
- Add `onError` handling to `<source>` element. ([@wadahiro](https://github.com/wadahiro) in [#6941](https://github.com/facebook/react/pull/6941))
- Handle `value` and `defaultValue` more accurately in the DOM. ([@jimfb](https://github.com/jimfb) in [#6406](https://github.com/facebook/react/pull/6406))
- Fix events issue in environments with mutated `Object.prototype`. ([@Weizenlol](https://github.com/Weizenlol) in [#6886](https://github.com/facebook/react/pull/6886))
- Fix issue where `is="null"` ended up in the DOM in Firefox. ([@darobin](https://github.com/darobin) in [#6896](https://github.com/facebook/react/pull/6896))
- Improved performance of text escaping by using [escape-html](https://github.com/component/escape-html). ([@aickin](https://github.com/aickin) in [#6862](https://github.com/facebook/react/pull/6862))
- Fix issue with `dangerouslySetInnerHTML` and SVG in Internet Explorer. ([@joshhunt](https://github.com/joshhunt) in [#6982](https://github.com/facebook/react/pull/6982))
- Fix issue with `<textarea>` placeholders. ([@jimfb](https://github.com/jimfb) in [#7002](https://github.com/facebook/react/pull/7002))
- Fix controlled vs uncontrolled detection of `<input type="radio"/>`. ([@jimfb](https://github.com/jimfb) in [#7003](https://github.com/facebook/react/pull/7003))
- Improve performance of updating text content. ([@trueadm](https://github.com/trueadm) in [#7005](https://github.com/facebook/react/pull/7005))
- Ensure controlled `<select>` components behave the same on initial render as they do on updates. ([@yiminghe](https://github.com/yiminghe) in [#5362](https://github.com/facebook/react/pull/5362))

### React Perf Add-on
- Add `isRunning()` API. ([@nfcampos](https://github.com/nfcampos) in [#6763](https://github.com/facebook/react/pull/6763))
- Improve accuracy of lifecycle hook timing. ([@gaearon](https://github.com/gaearon) in [#6858](https://github.com/facebook/react/pull/6858))
- Fix internal errors when using ReactPerf with portal components. ([@gaearon](https://github.com/gaearon) in [#6860](https://github.com/facebook/react/pull/6860))
- Fix performance regression. ([@sophiebits](https://github.com/sophiebits) in [#6770](https://github.com/facebook/react/pull/6770))
- Add warning that ReactPerf is not enabled in production. ([@sashashakun](https://github.com/sashashakun) in [#6884](https://github.com/facebook/react/pull/6884))

### React CSSTransitionGroup Add-on
- Fix timing issue with `null` node. ([@keyanzhang](https://github.com/keyanzhang) in [#6958](https://github.com/facebook/react/pull/6958))

### React Native Renderer
- Dependencies on React Native modules use CommonJS requires instead of providesModule. ([@davidaurelio](https://github.com/davidaurelio) in [#6715](https://github.com/facebook/react/pull/6715))


## 15.1.0 (May 20, 2016)

### React
- Ensure we're using the latest `object-assign`, which has protection against a non-spec-compliant native `Object.assign`. ([@zpao](https://github.com/zpao) in [#6681](https://github.com/facebook/react/pull/6681))
- Add a new warning to communicate that `props` objects passed to `createElement` must be plain objects. ([@richardscarrott](https://github.com/richardscarrott) in [#6134](https://github.com/facebook/react/pull/6134))
- Fix a batching bug resulting in some lifecycle methods incorrectly being called multiple times. ([@sophiebits](https://github.com/sophiebits) in [#6650](https://github.com/facebook/react/pull/6650))

### React DOM
- Fix regression in custom elements support. ([@jscissr](https://github.com/jscissr) in [#6570](https://github.com/facebook/react/pull/6570))
- Stop incorrectly warning about using `onScroll` event handler with server rendering. ([@Aweary](https://github.com/Aweary) in [#6678](https://github.com/facebook/react/pull/6678))
- Fix grammar in the controlled input warning. ([@jakeboone02](https://github.com/jakeboone02) in [#6657](https://github.com/facebook/react/pull/6657))
- Fix issue preventing `<object>` nodes from being able to read `<param>` nodes in IE. ([@syranide](https://github.com/syranide) in [#6691](https://github.com/facebook/react/pull/6691))
- Fix issue resulting in crash when using experimental error boundaries with server rendering. ([@jimfb](https://github.com/jimfb) in [#6694](https://github.com/facebook/react/pull/6694))
- Add additional information to the controlled input warning. ([@borisyankov](https://github.com/borisyankov) in [#6341](https://github.com/facebook/react/pull/6341))

### React Perf Add-on
- Completely rewritten to collect data more accurately and to be easier to maintain. ([@gaearon](https://github.com/gaearon) in [#6647](https://github.com/facebook/react/pull/6647), [#6046](https://github.com/facebook/react/pull/6046))

### React Native Renderer
- Remove some special cases for platform specific branching. ([@sebmarkbage](https://github.com/sebmarkbage) in [#6660](https://github.com/facebook/react/pull/6660))
- Remove use of `merge` utility. ([@sebmarkbage](https://github.com/sebmarkbage) in [#6634](https://github.com/facebook/react/pull/6634))
- Renamed some modules to better indicate usage ([@javache](https://github.com/javache) in [#6643](https://github.com/facebook/react/pull/6643))


## 15.0.2 (April 29, 2016)

### React
- Removed extraneous files from npm package. ([@gaearon](https://github.com/gaearon) in [#6388](https://github.com/facebook/react/pull/6388))
- Ensure `componentWillUnmount` is only called once. ([@jimfb](https://github.com/jimfb) in [#6613](https://github.com/facebook/react/pull/6613))

### ReactDOM
- Fixed bug resulting in disabled buttons responding to mouse events in IE. ([@nhunzaker](https://github.com/nhunzaker) in [#6215](https://github.com/facebook/react/pull/6215))
- Ensure `<option>`s are correctly selected when inside `<optgroup>`. ([@trevorsmith](https://github.com/trevorsmith) in [#6442](https://github.com/facebook/react/pull/6442))
- Restore support for rendering into a shadow root. ([@Wildhoney](https://github.com/Wildhoney) in [#6462](https://github.com/facebook/react/pull/6462))
- Ensure nested `<body>` elements are caught when warning for invalid markup. ([@keyanzhang](https://github.com/keyanzhang) in [#6469](https://github.com/facebook/react/pull/6469))
- Improve warning when encountering multiple elements with the same key. ([@hkal](https://github.com/hkal) in [#6500](https://github.com/facebook/react/pull/6500))

### React TestUtils Add-on
- Ensure that functional components do not have an owner. ([@gaearon](https://github.com/gaearon) in [#6362](https://github.com/facebook/react/pull/6362))
- Handle invalid arguments to `scryRenderedDOMComponentsWithClass` better. ([@ipeters90](https://github.com/ipeters90) in [#6529](https://github.com/facebook/react/pull/6529))

### React Perf Add-on
- Ignore DOM operations that occur outside the batch operation. ([@gaearon](https://github.com/gaearon) in [#6516](https://github.com/facebook/react/pull/6516))

### React Native Renderer
- These files are now shipped inside the React npm package. They have no impact on React core or ReactDOM.


## 15.0.1 (April 8, 2016)

### React
- Restore `React.__spread` API to unbreak code compiled with some tools making use of this undocumented API. It is now officially deprecated. ([@zpao](https://github.com/zpao) in [#6444](https://github.com/facebook/react/pull/6444))

### ReactDOM
- Fixed issue resulting in loss of cursor position in controlled inputs. ([@sophiebits](https://github.com/sophiebits) in [#6449](https://github.com/facebook/react/pull/6449))


## 15.0.0 (April 7, 2016)

### Major changes

- **Initial render now uses `document.createElement` instead of generating HTML.** Previously we would generate a large string of HTML and then set `node.innerHTML`. At the time, this was decided to be faster than using `document.createElement` for the majority of cases and browsers that we supported. Browsers have continued to improve and so overwhelmingly this is no longer true. By using `createElement` we can make other parts of React faster. ([@sophiebits](https://github.com/sophiebits) in [#5205](https://github.com/facebook/react/pull/5205))
- **`data-reactid` is no longer on every node.** As a result of using `document.createElement`, we can prime the node cache as we create DOM nodes, allowing us to skip a potential lookup (which used the `data-reactid` attribute). Root nodes will have a `data-reactroot` attribute and server generated markup will still contain `data-reactid`. ([@sophiebits](https://github.com/sophiebits) in [#5205](https://github.com/facebook/react/pull/5205))
- **No more extra `<span>`s.** ReactDOM will now render plain text nodes interspersed with comment nodes that are used for demarcation. This gives us the same ability to update individual pieces of text, without creating extra nested nodes. If you were targeting these `<span>`s in your CSS, you will need to adjust accordingly. You can always render them explicitly in your components. ([@mwiencek](https://github.com/mwiencek) in [#5753](https://github.com/facebook/react/pull/5753))
- **Rendering `null` now uses comment nodes.** Previously `null` would render to `<noscript>` elements. We now use comment nodes. This may cause issues if making use of `:nth-child` CSS selectors. While we consider this rendering behavior an implementation detail of React, it's worth noting the potential problem. ([@sophiebits](https://github.com/sophiebits) in [#5451](https://github.com/facebook/react/pull/5451))
- **Functional components can now return `null`.** We added support for [defining stateless components as functions](/react/blog/2015/09/10/react-v0.14-rc1.html#stateless-function-components) in React 0.14. However, React 0.14 still allowed you to define a class component without extending `React.Component` or using `React.createClass()`, so [we couldn’t reliably tell if your component is a function or a class](https://github.com/facebook/react/issues/5355), and did not allow returning `null` from it. This issue is solved in React 15, and you can now return `null` from any component, whether it is a class or a function. ([@jimfb](https://github.com/jimfb) in [#5884](https://github.com/facebook/react/pull/5884))
- **Improved SVG support.** All SVG tags are now fully supported. (Uncommon SVG tags are not present on the `React.DOM` element helper, but JSX and `React.createElement` work on all tag names.) All SVG attributes that are implemented by the browsers should be supported too. If you find any attributes that we have missed, please [let us know in this issue](https://github.com/facebook/react/issues/1657). ([@zpao](https://github.com/zpao) in [#6243](https://github.com/facebook/react/pull/6243))

### Breaking changes

- **No more extra `<span>`s.**
- **`React.cloneElement()` now resolves `defaultProps`.** We fixed a bug in `React.cloneElement()` that some components may rely on. If some of the `props` received by `cloneElement()` are `undefined`, it used to return an element with `undefined` values for those props. We’re changing it to be consistent with `createElement()`. Now any `undefined` props passed to `cloneElement()` are resolved to the corresponding component’s `defaultProps`. ([@truongduy134](https://github.com/truongduy134) in [#5997](https://github.com/facebook/react/pull/5997))
- **`ReactPerf.getLastMeasurements()` is opaque.** This change won’t affect applications but may break some third-party tools. We are [revamping `ReactPerf` implementation](https://github.com/facebook/react/pull/6046) and plan to release it during the 15.x cycle. The internal performance measurement format is subject to change so, for the time being, we consider the return value of `ReactPerf.getLastMeasurements()` an opaque data structure that should not be relied upon. ([@gaearon](https://github.com/gaearon) in [#6286](https://github.com/facebook/react/pull/6286))

#### Removed deprecations

These deprecations were introduced nine months ago in v0.14 with a warning and are removed:

- Deprecated APIs are removed from the `React` top-level export: `findDOMNode`, `render`, `renderToString`, `renderToStaticMarkup`, and `unmountComponentAtNode`. As a reminder, they are now available on `ReactDOM` and `ReactDOMServer`. ([@jimfb](https://github.com/jimfb) in [#5832](https://github.com/facebook/react/pull/5832))
- Deprecated addons are removed: `batchedUpdates` and `cloneWithProps`. ([@jimfb](https://github.com/jimfb) in [#5859](https://github.com/facebook/react/pull/5859), [@zpao](https://github.com/zpao) in [#6016](https://github.com/facebook/react/pull/6016))
- Deprecated component instance methods are removed: `setProps`, `replaceProps`, and `getDOMNode`. ([@jimfb](https://github.com/jimfb) in [#5570](https://github.com/facebook/react/pull/5570))
- Deprecated CommonJS `react/addons` entry point is removed. As a reminder, you should use separate `react-addons-*` packages instead. This only applies if you use the CommonJS builds. ([@gaearon](https://github.com/gaearon) in [#6285](https://github.com/facebook/react/pull/6285))
- Passing `children` to void elements like `<input>` was deprecated, and now throws an error. ([@jonhester](https://github.com/jonhester) in [#3372](https://github.com/facebook/react/pull/3372))
- React-specific properties on DOM `refs` (e.g. `this.refs.div.props`) were deprecated, and are removed now. ([@jimfb](https://github.com/jimfb) in [#5495](https://github.com/facebook/react/pull/5495))

### New deprecations, introduced with a warning

Each of these changes will continue to work as before with a new warning until the release of React 16 so you can upgrade your code gradually.

- `LinkedStateMixin` and `valueLink` are now deprecated due to very low popularity. If you need this, you can use a wrapper component that implements the same behavior: [react-linked-input](https://www.npmjs.com/package/react-linked-input). ([@jimfb](https://github.com/jimfb) in [#6127](https://github.com/facebook/react/pull/6127))
- Future versions of React will treat `<input value={null}>` as a request to clear the input. However, React 0.14 has been ignoring `value={null}`. React 15 warns you on a `null` input value and offers you to clarify your intention. To fix the warning, you may explicitly pass an empty string to clear a controlled input, or pass `undefined` to make the input uncontrolled. ([@antoaravinth](https://github.com/antoaravinth) in [#5048](https://github.com/facebook/react/pull/5048))
- `ReactPerf.printDOM()` was renamed to `ReactPerf.printOperations()`, and `ReactPerf.getMeasurementsSummaryMap()` was renamed to `ReactPerf.getWasted()`. ([@gaearon](https://github.com/gaearon) in [#6287](https://github.com/facebook/react/pull/6287))

### New helpful warnings

- If you use a minified copy of the _development_ build, React DOM kindly encourages you to use the faster production build instead. ([@sophiebits](https://github.com/sophiebits) in [#5083](https://github.com/facebook/react/pull/5083))
- React DOM: When specifying a unit-less CSS value as a string, a future version will not add `px` automatically. This version now warns in this case (ex: writing `style={{width: '300'}}`. Unitless *number* values like `width: 300` are unchanged. ([@pluma](https://github.com/pluma) in [#5140](https://github.com/facebook/react/pull/5140))
- Synthetic Events will now warn when setting and accessing properties (which will not get cleared appropriately), as well as warn on access after an event has been returned to the pool. ([@kentcdodds](https://github.com/kentcdodds) in [#5940](https://github.com/facebook/react/pull/5940) and [@koba04](https://github.com/koba04) in [#5947](https://github.com/facebook/react/pull/5947))
- Elements will now warn when attempting to read `ref` and `key` from the props. ([@prometheansacrifice](https://github.com/prometheansacrifice) in [#5744](https://github.com/facebook/react/pull/5744))
- React will now warn if you pass a different `props` object to `super()` in the constructor. ([@prometheansacrifice](https://github.com/prometheansacrifice) in [#5346](https://github.com/facebook/react/pull/5346))
- React will now warn if you call `setState()` inside `getChildContext()`. ([@raineroviir](https://github.com/raineroviir) in [#6121](https://github.com/facebook/react/pull/6121))
- React DOM now attempts to warn for mistyped event handlers on DOM elements, such as `onclick` which should be `onClick`. ([@ali](https://github.com/ali) in [#5361](https://github.com/facebook/react/pull/5361))
- React DOM now warns about `NaN` values in `style`. ([@jontewks](https://github.com/jontewks) in [#5811](https://github.com/facebook/react/pull/5811))
- React DOM now warns if you specify both `value` and `defaultValue` for an input. ([@mgmcdermott](https://github.com/mgmcdermott) in [#5823](https://github.com/facebook/react/pull/5823))
- React DOM now warns if an input switches between being controlled and uncontrolled. ([@TheBlasfem](https://github.com/TheBlasfem) in [#5864](https://github.com/facebook/react/pull/5864))
- React DOM now warns if you specify `onFocusIn` or `onFocusOut` handlers as they are unnecessary in React. ([@jontewks](https://github.com/jontewks) in [#6296](https://github.com/facebook/react/pull/6296))
- React now prints a descriptive error message when you pass an invalid callback as the last argument to `ReactDOM.render()`, `this.setState()`, or `this.forceUpdate()`. ([@conorhastings](https://github.com/conorhastings) in [#5193](https://github.com/facebook/react/pull/5193) and [@gaearon](https://github.com/gaearon) in [#6310](https://github.com/facebook/react/pull/6310))
- Add-Ons: `TestUtils.Simulate()` now prints a helpful message if you attempt to use it with shallow rendering. ([@conorhastings](https://github.com/conorhastings) in [#5358](https://github.com/facebook/react/pull/5358))
- PropTypes: `arrayOf()` and `objectOf()` provide better error messages for invalid arguments. ([@chicoxyzzy](https://github.com/chicoxyzzy) in [#5390](https://github.com/facebook/react/pull/5390))

### Notable bug fixes

- Fixed multiple small memory leaks. ([@sophiebits](https://github.com/sophiebits) in [#4983](https://github.com/facebook/react/pull/4983) and [@victor-homyakov](https://github.com/victor-homyakov) in [#6309](https://github.com/facebook/react/pull/6309))
- Input events are handled more reliably in IE 10 and IE 11; spurious events no longer fire when using a placeholder. ([@jquense](https://github.com/jquense) in [#4051](https://github.com/facebook/react/pull/4051))
- The `componentWillReceiveProps()` lifecycle method is now consistently called when `context` changes. ([@milesj](https://github.com/milesj) in [#5787](https://github.com/facebook/react/pull/5787))
- `React.cloneElement()` doesn’t append slash to an existing `key` when used inside `React.Children.map()`. ([@ianobermiller](https://github.com/ianobermiller) in [#5892](https://github.com/facebook/react/pull/5892))
- React DOM now supports the `cite` and `profile` HTML attributes. ([@AprilArcus](https://github.com/AprilArcus) in [#6094](https://github.com/facebook/react/pull/6094) and [@saiichihashimoto](https://github.com/saiichihashimoto) in [#6032](https://github.com/facebook/react/pull/6032))
- React DOM now supports `cssFloat`, `gridRow` and `gridColumn` CSS properties. ([@stevenvachon](https://github.com/stevenvachon) in [#6133](https://github.com/facebook/react/pull/6133) and  [@mnordick](https://github.com/mnordick) in [#4779](https://github.com/facebook/react/pull/4779))
- React DOM now correctly handles `borderImageOutset`, `borderImageWidth`, `borderImageSlice`, `floodOpacity`, `strokeDasharray`, and `strokeMiterlimit` as unitless CSS properties. ([@rofrischmann](https://github.com/rofrischmann) in [#6210](https://github.com/facebook/react/pull/6210) and [#6270](https://github.com/facebook/react/pull/6270))
- React DOM now supports the `onAnimationStart`, `onAnimationEnd`, `onAnimationIteration`, `onTransitionEnd`, and `onInvalid` events. Support for `onLoad` has been added to `object` elements. ([@tomduncalf](https://github.com/tomduncalf) in [#5187](https://github.com/facebook/react/pull/5187),  [@milesj](https://github.com/milesj) in [#6005](https://github.com/facebook/react/pull/6005), and [@ara4n](https://github.com/ara4n) in [#5781](https://github.com/facebook/react/pull/5781))
- React DOM now defaults to using DOM attributes instead of properties, which fixes a few edge case bugs. Additionally the nullification of values (ex: `href={null}`) now results in the forceful removal, no longer trying to set to the default value used by browsers in the absence of a value. ([@syranide](https://github.com/syranide) in [#1510](https://github.com/facebook/react/pull/1510))
- React DOM does not mistakenly coerce `children` to strings for Web Components. ([@jimfb](https://github.com/jimfb) in [#5093](https://github.com/facebook/react/pull/5093))
- React DOM now correctly normalizes SVG `<use>` events. ([@edmellum](https://github.com/edmellum) in [#5720](https://github.com/facebook/react/pull/5720))
- React DOM does not throw if a `<select>` is unmounted while its `onChange` handler is executing. ([@sambev](https://github.com/sambev) in [#6028](https://github.com/facebook/react/pull/6028))
- React DOM does not throw in Windows 8 apps. ([@Andrew8xx8](https://github.com/Andrew8xx8) in [#6063](https://github.com/facebook/react/pull/6063))
- React DOM does not throw when asynchronously unmounting a child with a `ref`. ([@yiminghe](https://github.com/yiminghe) in [#6095](https://github.com/facebook/react/pull/6095))
- React DOM no longer forces synchronous layout because of scroll position tracking. ([@syranide](https://github.com/syranide) in [#2271](https://github.com/facebook/react/pull/2271))
- `Object.is` is used in a number of places to compare values, which leads to fewer false positives, especially involving `NaN`. In particular, this affects the `shallowCompare` add-on. ([@chicoxyzzy](https://github.com/chicoxyzzy) in [#6132](https://github.com/facebook/react/pull/6132))
- Add-Ons: ReactPerf no longer instruments adding or removing an event listener because they don’t really touch the DOM due to event delegation. ([@antoaravinth](https://github.com/antoaravinth) in [#5209](https://github.com/facebook/react/pull/5209))

### Other improvements

- React now uses `loose-envify` instead of `envify` so it installs fewer transitive dependencies. ([@qerub](https://github.com/qerub) in [#6303](https://github.com/facebook/react/pull/6303))
- Shallow renderer now exposes `getMountedInstance()`. ([@glenjamin](https://github.com/glenjamin) in [#4918](https://github.com/facebook/react/pull/4918))
- Shallow renderer now returns the rendered output from `render()`. ([@simonewebdesign](https://github.com/simonewebdesign) in [#5411](https://github.com/facebook/react/pull/5411))
- React no longer depends on ES5 *shams* for `Object.create` and `Object.freeze` in older environments. It still, however, requires ES5 *shims* in those environments. ([@dgreensp](https://github.com/dgreensp) in [#4959](https://github.com/facebook/react/pull/4959))
- React DOM now allows `data-` attributes with names that start with numbers. ([@nLight](https://github.com/nLight) in [#5216](https://github.com/facebook/react/pull/5216))
- React DOM adds a new `suppressContentEditableWarning` prop for components like [Draft.js](https://draftjs.org/) that intentionally manage `contentEditable` children with React. ([@mxstbr](https://github.com/mxstbr) in [#6112](https://github.com/facebook/react/pull/6112))
- React improves the performance for `createClass()` on complex specs. ([@sophiebits](https://github.com/sophiebits) in [#5550](https://github.com/facebook/react/pull/5550))

## 0.14.10 (October 14, 2020)

### React

* Backport support for the [new JSX transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) to 0.14.x. ([@lunaruan](https://github.com/lunaruan) in [#18299](https://github.com/facebook/react/pull/18299) and [@gaearon](https://github.com/gaearon) in [#20024](https://github.com/facebook/react/pull/20024))

## 0.14.8 (March 29, 2016)

### React
- Fixed memory leak when rendering on the server

## 0.14.7 (January 28, 2016)

### React
- Fixed bug with `<option>` tags when using `dangerouslySetInnerHTML`
- Fixed memory leak in synthetic event system

### React TestUtils Add-on
- Fixed bug with calling `setState` in `componentWillMount` when using shallow rendering


## 0.14.6 (January 6, 2016)

### React
- Updated `fbjs` dependency to pick up change affecting handling of undefined document.


## 0.14.5 (December 29, 2015)

### React
- More minor internal changes for better compatibility with React Native


## 0.14.4 (December 29, 2015)

### React
- Minor internal changes for better compatibility with React Native

### React DOM
- The `autoCapitalize` and `autoCorrect` props are now set as attributes in the DOM instead of properties to improve cross-browser compatibility
- Fixed bug with controlled `<select>` elements not handling updates properly

### React Perf Add-on
- Some DOM operation names have been updated for clarity in the output of `.printDOM()`


## 0.14.3 (November 18, 2015)

### React DOM
- Added support for `nonce` attribute for `<script>` and `<style>` elements
- Added support for `reversed` attribute for `<ol>` elements

### React TestUtils Add-on
- Fixed bug with shallow rendering and function refs

### React CSSTransitionGroup Add-on
- Fixed bug resulting in timeouts firing incorrectly when mounting and unmounting rapidly

### React on Bower
- Added `react-dom-server.js` to expose `renderToString` and `renderToStaticMarkup` for usage in the browser


## 0.14.2 (November 2, 2015)

### React DOM
- Fixed bug with development build preventing events from firing in some versions of Internet Explorer & Edge
- Fixed bug with development build when using es5-sham in older versions of Internet Explorer
- Added support for `integrity` attribute
- Fixed bug resulting in `children` prop being coerced to a string for custom elements, which was not the desired behavior
- Moved `react` from `dependencies` to `peerDependencies` to match expectations and align with `react-addons-*` packages


## 0.14.1 (October 28, 2015)

### React DOM
- Fixed bug where events wouldn't fire in old browsers when using React in development mode
- Fixed bug preventing use of `dangerouslySetInnerHTML` with Closure Compiler Advanced mode
- Added support for `srcLang`, `default`, and `kind` attributes for `<track>` elements
- Added support for `color` attribute
- Ensured legacy `.props` access on DOM nodes is updated on re-renders

### React TestUtils Add-on
- Fixed `scryRenderedDOMComponentsWithClass` so it works with SVG

### React CSSTransitionGroup Add-on
- Fix bug preventing `0` to be used as a timeout value

### React on Bower
- Added `react-dom.js` to `main` to improve compatibility with tooling


## 0.14.0 (October 7, 2015)

### Major changes

- Split the main `react` package into two: `react` and `react-dom`.  This paves the way to writing components that can be shared between the web version of React and React Native.  This means you will need to include both files and some functions have been moved from `React` to `ReactDOM`.
- Addons have been moved to separate packages (`react-addons-clone-with-props`, `react-addons-create-fragment`, `react-addons-css-transition-group`, `react-addons-linked-state-mixin`, `react-addons-perf`, `react-addons-pure-render-mixin`, `react-addons-shallow-compare`, `react-addons-test-utils`, `react-addons-transition-group`, `react-addons-update`, `ReactDOM.unstable_batchedUpdates`).
- Stateless functional components - React components were previously created using React.createClass or using ES6 classes.  This release adds a [new syntax](https://reactjs.org/docs/reusable-components.html#stateless-functions) where a user defines a single [stateless render function](https://reactjs.org/docs/reusable-components.html#stateless-functions) (with one parameter: `props`) which returns a JSX element, and this function may be used as a component.
- Refs to DOM components as the DOM node itself. Previously the only useful thing you can do with a DOM component is call `getDOMNode()` to get the underlying DOM node. Starting with this release, a ref to a DOM component _is_ the actual DOM node. **Note that refs to custom (user-defined) components work exactly as before; only the built-in DOM components are affected by this change.**


### Breaking changes

- `React.initializeTouchEvents` is no longer necessary and has been removed completely. Touch events now work automatically.
- Add-Ons: Due to the DOM node refs change mentioned above, `TestUtils.findAllInRenderedTree` and related helpers are no longer able to take a DOM component, only a custom component.
- The `props` object is now frozen, so mutating props after creating a component element is no longer supported. In most cases, [`React.cloneElement`](https://reactjs.org/docs/react-api.html#cloneelement) should be used instead. This change makes your components easier to reason about and enables the compiler optimizations mentioned above.
- Plain objects are no longer supported as React children; arrays should be used instead. You can use the [`createFragment`](https://reactjs.org/docs/create-fragment.html) helper to migrate, which now returns an array.
- Add-Ons: `classSet` has been removed. Use [classnames](https://github.com/JedWatson/classnames) instead.
- Web components (custom elements) now use native property names.  Eg: `class` instead of `className`.

### Deprecations

- `this.getDOMNode()` is now deprecated and `ReactDOM.findDOMNode(this)` can be used instead. Note that in the common case, `findDOMNode` is now unnecessary since a ref to the DOM component is now the actual DOM node.
- `setProps` and `replaceProps` are now deprecated. Instead, call ReactDOM.render again at the top level with the new props.
- ES6 component classes must now extend `React.Component` in order to enable stateless function components. The [ES3 module pattern](https://reactjs.org/blog/2015/01/27/react-v0.13.0-beta-1.html#other-languages) will continue to work.
- Reusing and mutating a `style` object between renders has been deprecated. This mirrors our change to freeze the `props` object.
- Add-Ons: `cloneWithProps` is now deprecated. Use [`React.cloneElement`](https://reactjs.org/docs/react-api.html#cloneelement) instead (unlike `cloneWithProps`, `cloneElement` does not merge `className` or `style` automatically; you can merge them manually if needed).
- Add-Ons: To improve reliability, `CSSTransitionGroup` will no longer listen to transition events. Instead, you should specify transition durations manually using props such as `transitionEnterTimeout={500}`.

### Notable enhancements

- Added `React.Children.toArray` which takes a nested children object and returns a flat array with keys assigned to each child. This helper makes it easier to manipulate collections of children in your `render` methods, especially if you want to reorder or slice `this.props.children` before passing it down. In addition, `React.Children.map` now returns plain arrays too.
- React uses `console.error` instead of `console.warn` for warnings so that browsers show a full stack trace in the console. (Our warnings appear when you use patterns that will break in future releases and for code that is likely to behave unexpectedly, so we do consider our warnings to be “must-fix” errors.)
- Previously, including untrusted objects as React children [could result in an XSS security vulnerability](http://danlec.com/blog/xss-via-a-spoofed-react-element). This problem should be avoided by properly validating input at the application layer and by never passing untrusted objects around your application code. As an additional layer of protection, [React now tags elements](https://github.com/facebook/react/pull/4832) with a specific [ES2015 (ES6) `Symbol`](http://www.2ality.com/2014/12/es6-symbols.html) in browsers that support it, in order to ensure that React never considers untrusted JSON to be a valid element. If this extra security protection is important to you, you should add a `Symbol` polyfill for older browsers, such as the one included by [Babel’s polyfill](https://babeljs.io/docs/usage/polyfill/).
- When possible, React DOM now generates XHTML-compatible markup.
- React DOM now supports these standard HTML attributes: `capture`, `challenge`, `inputMode`, `is`, `keyParams`, `keyType`, `minLength`, `summary`, `wrap`. It also now supports these non-standard attributes: `autoSave`, `results`, `security`.
- React DOM now supports these SVG attributes, which render into namespaced attributes: `xlinkActuate`, `xlinkArcrole`, `xlinkHref`, `xlinkRole`, `xlinkShow`, `xlinkTitle`, `xlinkType`, `xmlBase`, `xmlLang`, `xmlSpace`.
- The `image` SVG tag is now supported by React DOM.
- In React DOM, arbitrary attributes are supported on custom elements (those with a hyphen in the tag name or an `is="..."` attribute).
- React DOM now supports these media events on `audio` and `video` tags: `onAbort`, `onCanPlay`, `onCanPlayThrough`, `onDurationChange`, `onEmptied`, `onEncrypted`, `onEnded`, `onError`, `onLoadedData`, `onLoadedMetadata`, `onLoadStart`, `onPause`, `onPlay`, `onPlaying`, `onProgress`, `onRateChange`, `onSeeked`, `onSeeking`, `onStalled`, `onSuspend`, `onTimeUpdate`, `onVolumeChange`, `onWaiting`.
- Many small performance improvements have been made.
- Many warnings show more context than before.
- Add-Ons: A [`shallowCompare`](https://github.com/facebook/react/pull/3355) add-on has been added as a migration path for `PureRenderMixin` in ES6 classes.
- Add-Ons: `CSSTransitionGroup` can now use [custom class names](https://github.com/facebook/react/blob/48942b85/docs/docs/10.1-animation.md#custom-classes) instead of appending `-enter-active` or similar to the transition name.

### New helpful warnings

- React DOM now warns you when nesting HTML elements invalidly, which helps you avoid surprising errors during updates.
- Passing `document.body` directly as the container to `ReactDOM.render` now gives a warning as doing so can cause problems with browser extensions that modify the DOM.
- Using multiple instances of React together is not supported, so we now warn when we detect this case to help you avoid running into the resulting problems.

### Notable bug fixes

- Click events are handled by React DOM more reliably in mobile browsers, particularly in Mobile Safari.
- SVG elements are created with the correct namespace in more cases.
- React DOM now renders `<option>` elements with multiple text children properly and renders `<select>` elements on the server with the correct option selected.
- When two separate copies of React add nodes to the same document (including when a browser extension uses React), React DOM tries harder not to throw exceptions during event handling.
- Using non-lowercase HTML tag names in React DOM (e.g., `React.createElement('DIV')`) no longer causes problems, though we continue to recommend lowercase for consistency with the JSX tag name convention (lowercase names refer to built-in components, capitalized names refer to custom components).
- React DOM understands that these CSS properties are unitless and does not append “px” to their values: `animationIterationCount`, `boxOrdinalGroup`, `flexOrder`, `tabSize`, `stopOpacity`.
- Add-Ons: When using the test utils, `Simulate.mouseEnter` and `Simulate.mouseLeave` now work.
- Add-Ons: ReactTransitionGroup now correctly handles multiple nodes being removed simultaneously.


### React Tools / Babel

#### Breaking Changes

- The `react-tools` package and `JSXTransformer.js` browser file [have been deprecated](https://reactjs.org/blog/2015/06/12/deprecating-jstransform-and-react-tools.html). You can continue using version `0.13.3` of both, but we no longer support them and recommend migrating to [Babel](https://babeljs.io), which has built-in support for React and JSX.

#### New Features

- Babel 5.8.24 introduces **Inlining React elements:** The `optimisation.react.inlineElements` transform converts JSX elements to object literals like `{type: 'div', props: ...}` instead of calls to `React.createElement`.  This should only be enabled in production, since it disables some development warnings/checks.
- Babel 5.8.24 introduces **Constant hoisting for React elements:** The `optimisation.react.constantElements` transform hoists element creation to the top level for subtrees that are fully static, which reduces calls to `React.createElement` and the resulting allocations. More importantly, it tells React that the subtree hasn’t changed so React can completely skip it when reconciling.  This should only be enabled in production, since it disables some development warnings/checks.


## 0.13.3 (May 8, 2015)

### React Core

#### New Features

* Added `clipPath` element and attribute for SVG
* Improved warnings for deprecated methods in plain JS classes

#### Bug Fixes

* Loosened `dangerouslySetInnerHTML` restrictions so `{__html: undefined}` will no longer throw
* Fixed extraneous context warning with non-pure `getChildContext`
* Ensure `replaceState(obj)` retains prototype of `obj`

### React with Add-ons

### Bug Fixes

* Test Utils: Ensure that shallow rendering works when components define `contextTypes`


## 0.13.2 (April 18, 2015)

### React Core

#### New Features

* Added `strokeDashoffset`, `flexPositive`, `flexNegative` to the list of unitless CSS properties
* Added support for more DOM properties:
  * `scoped` - for `<style>` elements
  * `high`, `low`, `optimum` - for `<meter>` elements
  * `unselectable` - IE-specific property to prevent user selection

#### Bug Fixes

* Fixed a case where re-rendering after rendering null didn't properly pass context
* Fixed a case where re-rendering after rendering with `style={null}` didn't properly update `style`
* Update `uglify` dependency to prevent a bug in IE8
* Improved warnings

### React with Add-Ons

#### Bug Fixes

* Immutability Helpers: Ensure it supports `hasOwnProperty` as an object key

### React Tools

* Improve documentation for new options


## 0.13.1 (March 16, 2015)

### React Core

#### Bug Fixes

* Don't throw when rendering empty `<select>` elements
* Ensure updating `style` works when transitioning from `null`

### React with Add-Ons

#### Bug Fixes

* TestUtils: Don't warn about `getDOMNode` for ES6 classes
* TestUtils: Ensure wrapped full page components (`<html>`, `<head>`, `<body>`) are treated as DOM components
* Perf: Stop double-counting DOM components

### React Tools

#### Bug Fixes

* Fix option parsing for `--non-strict-es6module`


## 0.13.0 (March 10, 2015)

### React Core

#### Breaking Changes

* Deprecated patterns that warned in 0.12 no longer work: most prominently, calling component classes without using JSX or React.createElement and using non-component functions with JSX or createElement
* Mutating `props` after an element is created is deprecated and will cause warnings in development mode; future versions of React will incorporate performance optimizations assuming that props aren't mutated
* Static methods (defined in `statics`) are no longer autobound to the component class
* `ref` resolution order has changed slightly such that a ref to a component is available immediately after its `componentDidMount` method is called; this change should be observable only if your component calls a parent component's callback within your `componentDidMount`, which is an anti-pattern and should be avoided regardless
* Calls to `setState` in life-cycle methods are now always batched and therefore asynchronous. Previously the first call on the first mount was synchronous.
* `setState` and `forceUpdate` on an unmounted component now warns instead of throwing. That avoids a possible race condition with Promises.
* Access to most internal properties has been completely removed, including `this._pendingState` and `this._rootNodeID`.

#### New Features

* Support for using ES6 classes to build React components; see the [v0.13.0 beta 1 notes](https://reactjs.org/blog/2015/01/27/react-v0.13.0-beta-1.html) for details.
* Added new top-level API `React.findDOMNode(component)`, which should be used in place of `component.getDOMNode()`. The base class for ES6-based components will not have `getDOMNode`. This change will enable some more patterns moving forward.
* Added a new top-level API `React.cloneElement(el, props)` for making copies of React elements – see the [v0.13 RC2 notes](https://reactjs.org/blog/2015/03/03/react-v0.13-rc2.html#react.cloneelement) for more details.
* New `ref` style, allowing a callback to be used in place of a name: `<Photo ref={(c) => this._photo = c} />` allows you to reference the component with `this._photo` (as opposed to `ref="photo"` which gives `this.refs.photo`).
* `this.setState()` can now take a function as the first argument for transactional state updates, such as `this.setState((state, props) => ({count: state.count + 1}));` – this means that you no longer need to use `this._pendingState`, which is now gone.
* Support for iterators and immutable-js sequences as children.

#### Deprecations

* `ComponentClass.type` is deprecated. Just use `ComponentClass` (usually as `element.type === ComponentClass`).
* Some methods that are available on `createClass`-based components are removed or deprecated from ES6 classes (`getDOMNode`, `replaceState`, `isMounted`, `setProps`, `replaceProps`).

### React with Add-Ons

#### New Features

* [`React.addons.createFragment` was added](https://reactjs.org/docs/create-fragment.html) for adding keys to entire sets of children.

#### Deprecations

* `React.addons.classSet` is now deprecated. This functionality can be replaced with several freely available modules. [classnames](https://www.npmjs.com/package/classnames) is one such module.
* Calls to `React.addons.cloneWithProps` can be migrated to use `React.cloneElement` instead – make sure to merge `style` and `className` manually if desired.

### React Tools

#### Breaking Changes

* When transforming ES6 syntax, `class` methods are no longer enumerable by default, which requires `Object.defineProperty`; if you support browsers such as IE8, you can pass `--target es3` to mirror the old behavior

#### New Features

* `--target` option is available on the jsx command, allowing users to specify and ECMAScript version to target.
  * `es5` is the default.
  * `es3` restores the previous default behavior. An additional transform is added here to ensure the use of reserved words as properties is safe (eg `this.static` will become `this['static']` for IE8 compatibility).
* The transform for the call spread operator has also been enabled.

### JSXTransformer

#### Breaking Changes

* The return value of `transform` now contains `sourceMap` as a JS object already, not an instance of `SourceMapGenerator`.

### JSX

#### Breaking Changes
* A change was made to how some JSX was parsed, specifically around the use of `>` or `}` when inside an element. Previously it would be treated as a string but now it will be treated as a parse error. The [`jsx_orphaned_brackets_transformer`](https://www.npmjs.com/package/jsx_orphaned_brackets_transformer) package on npm can be used to find and fix potential issues in your JSX code.


## 0.12.2 (December 18, 2014)

### React Core

* Added support for more HTML attributes: `formAction`, `formEncType`, `formMethod`, `formTarget`, `marginHeight`, `marginWidth`
* Added `strokeOpacity` to the list of unitless CSS properties
* Removed trailing commas (allows npm module to be bundled and used in IE8)
* Fixed bug resulting in error when passing `undefined` to `React.createElement` - now there is a useful warning

### React Tools

* JSX-related transforms now always use double quotes for props and `displayName`


## 0.12.1 (November 18, 2014)

### React Tools

* Types transform updated with latest support
* jstransform version updated with improved ES6 transforms
* Explicit Esprima dependency removed in favor of using Esprima information exported by jstransform


## 0.12.0 (October 28, 2014)

### React Core

#### Breaking Changes

* `key` and `ref` moved off props object, now accessible on the element directly
* React is now BSD licensed with accompanying Patents grant
* Default prop resolution has moved to Element creation time instead of mount time, making them effectively static
* `React.__internals` is removed - it was exposed for DevTools which no longer needs access
* Composite Component functions can no longer be called directly - they must be wrapped with `React.createFactory` first. This is handled for you when using JSX.

#### New Features

* Spread operator (`{...}`) introduced to deprecate `this.transferPropsTo`
* Added support for more HTML attributes: `acceptCharset`, `classID`, `manifest`

#### Deprecations

* `React.renderComponent` --> `React.render`
* `React.renderComponentToString` --> `React.renderToString`
* `React.renderComponentToStaticMarkup` --> `React.renderToStaticMarkup`
* `React.isValidComponent` --> `React.isValidElement`
* `React.PropTypes.component` --> `React.PropTypes.element`
* `React.PropTypes.renderable` --> `React.PropTypes.node`
* **DEPRECATED** `React.isValidClass`
* **DEPRECATED** `instance.transferPropsTo`
* **DEPRECATED** Returning `false` from event handlers to preventDefault
* **DEPRECATED** Convenience Constructor usage as function, instead wrap with `React.createFactory`
* **DEPRECATED** use of `key={null}` to assign implicit keys

#### Bug Fixes

* Better handling of events and updates in nested results, fixing value restoration in "layered" controlled components
* Correctly treat `event.getModifierState` as case sensitive
* Improved normalization of `event.charCode`
* Better error stacks when involving autobound methods
* Removed DevTools message when the DevTools are installed
* Correctly detect required language features across browsers
* Fixed support for some HTML attributes:
  * `list` updates correctly now
  * `scrollLeft`, `scrollTop` removed, these should not be specified as props
* Improved error messages

### React With Addons

#### New Features

* `React.addons.batchedUpdates` added to API for hooking into update cycle

#### Breaking Changes

* `React.addons.update` uses `assign` instead of `copyProperties` which does `hasOwnProperty` checks. Properties on prototypes will no longer be updated correctly.

#### Bug Fixes

* Fixed some issues with CSS Transitions

### JSX

#### Breaking Changes

* Enforced convention: lower case tag names are always treated as HTML tags, upper case tag names are always treated as composite components
* JSX no longer transforms to simple function calls

#### New Features

* `@jsx React.DOM` no longer required
* spread (`{...}`) operator introduced to allow easier use of props

#### Bug Fixes

* JSXTransformer: Make sourcemaps an option when using APIs directly (eg, for react-rails)


## 0.11.2 (September 16, 2014)

### React Core

#### New Features

* Added support for `<dialog>` element and associated `open` attribute
* Added support for `<picture>` element and associated `media` and `sizes` attributes
* Added `React.createElement` API in preparation for React v0.12
  * `React.createDescriptor` has been deprecated as a result

### JSX

* `<picture>` is now parsed into `React.DOM.picture`

### React Tools

* Update `esprima` and `jstransform` for correctness fixes
* The `jsx` executable now exposes a `--strip-types` flag which can be used to remove TypeScript-like type annotations
  * This option is also exposed to `require('react-tools').transform` as `stripTypes`

## 0.11.1 (July 24, 2014)

### React Core

#### Bug Fixes
* `setState` can be called inside `componentWillMount` in non-DOM environments
* `SyntheticMouseEvent.getEventModifierState` correctly renamed to `getModifierState`
* `getModifierState` correctly returns a `boolean`
* `getModifierState` is now correctly case sensitive
* Empty Text node used in IE8 `innerHTML` workaround is now removed, fixing rerendering in certain cases

### JSX
* Fix duplicate variable declaration in JSXTransformer (caused issues in some browsers)


## 0.11.0 (July 17, 2014)

### React Core

#### Breaking Changes
* `getDefaultProps()` is now called once per class and shared across all instances
* `MyComponent()` now returns a descriptor, not an instance
* `React.isValidComponent` and `React.PropTypes.component` validate *descriptors*, not component instances
* Custom `propType` validators should return an `Error` instead of logging directly

#### New Features
* Rendering to `null`
* Keyboard events include normalized `e.key` and `e.getModifierState()` properties
* New normalized `onBeforeInput` event
* `React.Children.count` has been added as a helper for counting the number of children

#### Bug Fixes

* Re-renders are batched in more cases
* Events: `e.view` properly normalized
* Added Support for more HTML attributes (`coords`, `crossOrigin`, `download`, `hrefLang`, `mediaGroup`, `muted`, `scrolling`, `shape`, `srcSet`, `start`, `useMap`)
* Improved SVG support
  * Changing `className` on a mounted SVG component now works correctly
  * Added support for elements `mask` and `tspan`
  * Added support for attributes `dx`, `dy`, `fillOpacity`, `fontFamily`, `fontSize`, `markerEnd`, `markerMid`, `markerStart`, `opacity`, `patternContentUnits`, `patternUnits`, `preserveAspectRatio`, `strokeDasharray`, `strokeOpacity`
* CSS property names with vendor prefixes (`Webkit`, `ms`, `Moz`, `O`) are now handled properly
* Duplicate keys no longer cause a hard error; now a warning is logged (and only one of the children with the same key is shown)
* `img` event listeners are now unbound properly, preventing the error "Two valid but unequal nodes with the same `data-reactid`"
* Added explicit warning when missing polyfills

### React With Addons
* PureRenderMixin: a mixin which helps optimize "pure" components
* Perf: a new set of tools to help with performance analysis
* Update: New `$apply` command to transform values
* TransitionGroup bug fixes with null elements, Android

### React NPM Module
* Now includes the pre-built packages under `dist/`.
* `envify` is properly listed as a dependency instead of a peer dependency

### JSX
* Added support for namespaces, eg `<Components.Checkbox />`
* JSXTransformer
  * Enable the same `harmony` features available in the command line with `<script type="text/jsx;harmony=true">`
  * Scripts are downloaded in parallel for more speed. They are still executed in order (as you would expect with normal script tags)
  * Fixed a bug preventing sourcemaps from working in Firefox

### React Tools Module
* Improved readme with usage and API information
* Improved ES6 transforms available with `--harmony` option
* Added `--source-map-inline` option to the `jsx` executable
* New `transformWithDetails` API which gives access to the raw sourcemap data


## 0.10.0 (March 21, 2014)

### React Core

#### New Features
* Added warnings to help migrate towards descriptors
* Made it possible to server render without React-related markup (`data-reactid`, `data-react-checksum`). This DOM will not be mountable by React. [Read the docs for `React.renderComponentToStaticMarkup`](https://reactjs.org/docs/top-level-api.html#react.rendercomponenttostaticmarkup)
* Added support for more attributes:
  * `srcSet` for `<img>` to specify images at different pixel ratios
  * `textAnchor` for SVG

#### Bug Fixes
* Ensure all void elements don’t insert a closing tag into the markup.
* Ensure `className={false}` behaves consistently
* Ensure `this.refs` is defined, even if no refs are specified.

### Addons

* `update` function to deal with immutable data. [Read the docs](https://reactjs.org/docs/update.html)

### react-tools
* Added an option argument to `transform` function. The only option supported is `harmony`, which behaves the same as `jsx --harmony` on the command line. This uses the ES6 transforms from [jstransform](https://github.com/facebook/jstransform).


## 0.9.0 (February 20, 2014)

### React Core

#### Breaking Changes

- The lifecycle methods `componentDidMount` and `componentDidUpdate` no longer receive the root node as a parameter; use `this.getDOMNode()` instead
- Whenever a prop is equal to `undefined`, the default value returned by `getDefaultProps` will now be used instead
- `React.unmountAndReleaseReactRootNode` was previously deprecated and has now been removed
- `React.renderComponentToString` is now synchronous and returns the generated HTML string
- Full-page rendering (that is, rendering the `<html>` tag using React) is now supported only when starting with server-rendered markup
- On mouse wheel events, `deltaY` is no longer negated
- When prop types validation fails, a warning is logged instead of an error thrown (with the production build of React, type checks are now skipped for performance)
- On `input`, `select`, and `textarea` elements, `.getValue()` is no longer supported; use `.getDOMNode().value` instead
- `this.context` on components is now reserved for internal use by React

#### New Features

- React now never rethrows errors, so stack traces are more accurate and Chrome's purple break-on-error stop sign now works properly
- Added support for SVG tags `defs`, `linearGradient`, `polygon`, `radialGradient`, `stop`
- Added support for more attributes:
  - `crossOrigin` for CORS requests
  - `download` and `hrefLang` for `<a>` tags
  - `mediaGroup` and `muted` for `<audio>` and `<video>` tags
  - `noValidate` and `formNoValidate` for forms
  - `property` for Open Graph `<meta>` tags
  - `sandbox`, `seamless`, and `srcDoc` for `<iframe>` tags
  - `scope` for screen readers
  - `span` for `<colgroup>` tags
- Added support for defining `propTypes` in mixins
- Added `any`, `arrayOf`, `component`, `oneOfType`, `renderable`, `shape` to `React.PropTypes`
- Added support for `statics` on component spec for static component methods
- On all events, `.currentTarget` is now properly set
- On keyboard events, `.key` is now polyfilled in all browsers for special (non-printable) keys
- On clipboard events, `.clipboardData` is now polyfilled in IE
- On drag events, `.dragTransfer` is now present
- Added support for `onMouseOver` and `onMouseOut` in addition to the existing `onMouseEnter` and `onMouseLeave` events
- Added support for `onLoad` and `onError` on `<img>` elements
- Added support for `onReset` on `<form>` elements
- The `autoFocus` attribute is now polyfilled consistently on `input`, `select`, and `textarea`

#### Bug Fixes

- React no longer adds an `__owner__` property to each component's `props` object; passed-in props are now never mutated
- When nesting top-level components (e.g., calling `React.renderComponent` within `componentDidMount`), events now properly bubble to the parent component
- Fixed a case where nesting top-level components would throw an error when updating
- Passing an invalid or misspelled propTypes type now throws an error
- On mouse enter/leave events, `.target`, `.relatedTarget`, and `.type` are now set properly
- On composition events, `.data` is now properly normalized in IE9 and IE10
- CSS property values no longer have `px` appended for the unitless properties `columnCount`, `flex`, `flexGrow`, `flexShrink`, `lineClamp`, `order`, `widows`
- Fixed a memory leak when unmounting children with a `componentWillUnmount` handler
- Fixed a memory leak when `renderComponentToString` would store event handlers
- Fixed an error that could be thrown when removing form elements during a click handler
- Boolean attributes such as `disabled` are rendered without a value (previously `disabled="true"`, now simply `disabled`)
- `key` values containing `.` are now supported
- Shortened `data-reactid` values for performance
- Components now always remount when the `key` property changes
- Event handlers are attached to `document` only when necessary, improving performance in some cases
- Events no longer use `.returnValue` in modern browsers, eliminating a warning in Chrome
- `scrollLeft` and `scrollTop` are no longer accessed on document.body, eliminating a warning in Chrome
- General performance fixes, memory optimizations, improvements to warnings and error messages

### React with Addons

- `React.addons.TestUtils` was added to help write unit tests
- `React.addons.TransitionGroup` was renamed to `React.addons.CSSTransitionGroup`
- `React.addons.TransitionGroup` was added as a more general animation wrapper
- `React.addons.cloneWithProps` was added for cloning components and modifying their props
- Bug fix for adding back nodes during an exit transition for CSSTransitionGroup
- Bug fix for changing `transitionLeave` in CSSTransitionGroup
- Performance optimizations for CSSTransitionGroup
- On checkbox `<input>` elements, `checkedLink` is now supported for two-way binding

### JSX Compiler and react-tools Package

- Whitespace normalization has changed; now space between two tags on the same line will be preserved, while newlines between two tags will be removed
- The `react-tools` npm package no longer includes the React core libraries; use the `react` package instead.
- `displayName` is now added in more cases, improving error messages and names in the React Dev Tools
- Fixed an issue where an invalid token error was thrown after a JSX closing tag
- `JSXTransformer` now uses source maps automatically in modern browsers
- `JSXTransformer` error messages now include the filename and problematic line contents when a file fails to parse

## 0.8.0 (December 19, 2013)

### React

* Added support for more attributes:
  * `rows` & `cols` for `<textarea>`
  * `defer` & `async` for `<script>`
  * `loop` for `<audio>` & `<video>`
  * `autoCorrect` for form fields (a non-standard attribute only supported by mobile WebKit)
* Improved error messages
* Fixed Selection events in IE11
* Added `onContextMenu` events

### React with Addons

* Fixed bugs with TransitionGroup when children were undefined
* Added support for `onTransition`

### react-tools

* Upgraded `jstransform` and `esprima-fb`

### JSXTransformer

* Added support for use in IE8
* Upgraded browserify, which reduced file size by ~65KB (16KB gzipped)


## 0.5.2, 0.4.2 (December 18, 2013)

### React

* Fixed a potential XSS vulnerability when using user content as a `key`: [CVE-2013-7035](https://groups.google.com/forum/#!topic/reactjs/OIqxlB2aGfU)


## 0.5.1 (October 29, 2013)

### React

* Fixed bug with `<input type="range">` and selection events.
* Fixed bug with selection and focus.
* Made it possible to unmount components from the document root.
* Fixed bug for `disabled` attribute handling on non-`<input>` elements.

### React with Addons

* Fixed bug with transition and animation event detection.


## 0.5.0 (October 16, 2013)

### React

* Memory usage improvements - reduced allocations in core which will help with GC pauses
* Performance improvements - in addition to speeding things up, we made some tweaks to stay out of slow path code in V8 and Nitro.
* Standardized prop -> DOM attribute process. This previously resulting in additional type checking and overhead as well as confusing cases for users. Now we will always convert your value to a string before inserting it into the DOM.
* Support for Selection events.
* Support for [Composition events](https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent).
* Support for additional DOM properties (`charSet`, `content`, `form`, `httpEquiv`, `rowSpan`, `autoCapitalize`).
* Support for additional SVG properties (`rx`, `ry`).
* Support for using `getInitialState` and `getDefaultProps` in mixins.
* Support mounting into iframes.
* Bug fixes for controlled form components.
* Bug fixes for SVG element creation.
* Added `React.version`.
* Added `React.isValidClass` - Used to determine if a value is a valid component constructor.
* Removed `React.autoBind` - This was deprecated in v0.4 and now properly removed.
* Renamed  `React.unmountAndReleaseReactRootNode` to `React.unmountComponentAtNode`.
* Began laying down work for refined performance analysis.
* Better support for server-side rendering - [react-page](https://github.com/facebook/react-page) has helped improve the stability for server-side rendering.
* Made it possible to use React in environments enforcing a strict [Content Security Policy](https://developer.mozilla.org/en-US/docs/Security/CSP/Introducing_Content_Security_Policy). This also makes it possible to use React to build Chrome extensions.

### React with Addons (New!)

* Introduced a separate build with several "addons" which we think can help improve the React experience. We plan to deprecate this in the long-term, instead shipping each as standalone pieces. [Read more in the docs](https://reactjs.org/docs/addons.html).

### JSX

* No longer transform `class` to `className` as part of the transform! This is a breaking change - if you were using `class`, you *must* change this to `className` or your components will be visually broken.
* Added warnings to the in-browser transformer to make it clear it is not intended for production use.
* Improved compatibility for Windows
* Improved support for maintaining line numbers when transforming.


## 0.4.1 (July 26, 2013)

### React

* `setState` callbacks are now executed in the scope of your component.
* `click` events now work on Mobile Safari.
* Prevent a potential error in event handling if `Object.prototype` is extended.
* Don't set DOM attributes to the string `"undefined"` on update when previously defined.
* Improved support for `<iframe>` attributes.
* Added checksums to detect and correct cases where server-side rendering markup mismatches what React expects client-side.

### JSXTransformer

* Improved environment detection so it can be run in a non-browser environment.


## 0.4.0 (July 17, 2013)

### React

* Switch from using `id` attribute to `data-reactid` to track DOM nodes. This allows you to integrate with other JS and CSS libraries more easily.
* Support for more DOM elements and attributes (e.g., `<canvas>`)
* Improved server-side rendering APIs. `React.renderComponentToString(<component>, callback)` allows you to use React on the server and generate markup which can be sent down to the browser.
* `prop` improvements: validation and default values. [Read our blog post for details...](https://reactjs.org/blog/2013/07/11/react-v0-4-prop-validation-and-default-values.html)
* Support for the `key` prop, which allows for finer control over reconciliation. [Read the docs for details...](https://reactjs.org/docs/multiple-components.html)
* Removed `React.autoBind`. [Read our blog post for details...](https://reactjs.org/blog/2013/07/02/react-v0-4-autobind-by-default.html)
* Improvements to forms. We've written wrappers around `<input>`, `<textarea>`, `<option>`, and `<select>` in order to standardize many inconsistencies in browser implementations. This includes support for `defaultValue`, and improved implementation of the `onChange` event, and circuit completion. [Read the docs for details...](https://reactjs.org/docs/forms.html)
* We've implemented an improved synthetic event system that conforms to the W3C spec.
* Updates to your component are batched now, which may result in a significantly faster re-render of components. `this.setState` now takes an optional callback as it's second parameter. If you were using `onClick={this.setState.bind(this, state)}` previously, you'll want to make sure you add a third parameter so that the event is not treated as the callback.

### JSX

* Support for comment nodes `<div>{/* this is a comment and won't be rendered */}</div>`
* Children are now transformed directly into arguments instead of being wrapped in an array
  E.g. `<div><Component1/><Component2/></div>` is transformed into `React.DOM.div(null, Component1(null), Component2(null))`.
  Previously this would be transformed into `React.DOM.div(null, [Component1(null), Component2(null)])`.
  If you were using React without JSX previously, your code should still work.

### react-tools

* Fixed a number of bugs when transforming directories
* No longer re-write `require()`s to be relative unless specified


## 0.3.3 (June 20, 2013)

### React

* Allow reusing the same DOM node to render different components. e.g. `React.renderComponent(<div/>, domNode); React.renderComponent(<span/>, domNode);` will work now.

### JSX

* Improved the in-browser transformer so that transformed scripts will execute in the expected scope. The allows components to be defined and used from separate files.

### react-tools

* Upgrade Commoner so `require` statements are no longer relativized when passing through the transformer. This was a feature needed when building React, but doesn't translate well for other consumers of `bin/jsx`.
* Upgraded our dependencies on Commoner and Recast so they use a different directory for their cache.
* Freeze our Esprima dependency.


## 0.3.2 (May 31, 2013)

### JSX

* Improved compatibility with other coding styles (specifically, multiple assignments with a single `var`).

### react-tools

* Switch from using the browserified build to shipping individual modules. This allows react-tools to be used with [browserify](https://github.com/substack/node-browserify).


## 0.3.1 (May 30, 2013)

### react-tools

* Fix bug in packaging resulting in broken module.


## 0.3.0 (May 29, 2013)

* Initial public release