Today, we are releasing React 17!

Learn more about React 17 and how to update to it on the official React blog.

React

• Add react/jsx-runtime and react/jsx-dev-runtime for the new JSX transform. (@lunaruan in #18299)
• Build component stacks from native error frames. (@sebmarkbage in #18561)
• Allow to specify displayName on context for improved stacks. (@eps1lon in #18224)
• Prevent 'use strict' from leaking in the UMD bundles. (@koba04 in #19614)
• Stop using fb.me for redirects. (@cylim in #19598)

React DOM

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

React DOM Server

• Make useCallback behavior consistent with useMemo for the server renderer. (@alexmckenley in #18783)
• Fix state leaking when a function component throws. (@pmaccart in #19212)

React Test Renderer

• Improve findByType error message. (@henryqdineen in #17439)

Concurrent Mode (Experimental)

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

Artifacts

• react: https://unpkg.com/react@17.0.1/umd/
• react-art: https://unpkg.com/react-art@17.0.1/umd/
• react-dom: https://unpkg.com/react-dom@17.0.1/umd/
• react-is: https://unpkg.com/react-is@17.0.1/umd/
• react-test-renderer: https://unpkg.com/react-test-renderer@17.0.1/umd/
• scheduler: https://unpkg.com/scheduler@0.20.1/umd/