• Export act from react f1338f

This release is identical to 18.2 but adds warnings for deprecated APIs and other changes that are needed for React 19.

Read the React 19 Upgrade Guide for more info.

React

• Allow writing to this.refs to support string ref codemod 909071
• Warn for deprecated findDOMNode outside StrictMode c3b283
• Warn for deprecated test-utils methods d4ea75
• Warn for deprecated Legacy Context outside StrictMode 415ee0
• Warn for deprecated string refs outside StrictMode #25383
• Warn for deprecated defaultProps for function componen...

React DOM

• Provide a component stack as a second argument to onRecoverableError. (@gnoff in #24591)
• Fix hydrating into document causing a blank page on mismatch. (@gnoff in #24523)
• Fix false positive hydration errors with Suspense. (@gnoff in #24480 and @acdlite in #24532)
• Fix ignored setState in Safari when adding an iframe. (@gaearon in #24459)

React DOM Server

• Pass information about server errors to the client. (@salazarm and @gnoff in #24551 and [#24591](https://gi...

React DOM

• Fix the false positive warning about react-dom/client when using UMD bundle. (@alireza-molaee in #24274)
• Fix suppressHydrationWarning to work in production too. (@gaearon in #24271)
• Fix componentWillUnmount firing twice inside of Suspense. (@acdlite in #24308)
• Fix some transition updates being ignored. (@acdlite in #24353)
• Fix useDeferredValue causing an infinite loop when passed an unmemoized value. (@acdlite in #24247)
• Fix throttling of revealing Suspense fallbacks. (@sunderls in [#24253](https://github.com/facebook/react/...

Below is a list of all new features, APIs, deprecations, and breaking changes. Read React 18 release post and React 18 upgrade guide for more information.

New Features

React

• 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...

React DOM

• Remove an unused dependency to address the SharedArrayBuffer cross-origin isolation warning. (@koba04 and @bvaughn in #20831, #20832, and #20840)

Artifacts

• react: https://unpkg.com/react@17.0.2/umd/
• react-art: https://unpkg.com/react-art@17.0.2/umd/
• react-dom: https://unpkg.com/react-dom@17.0.2/umd/
• react-is: https://unpkg.com/react-is@17.0.2/umd/
• react-test-renderer: https://unpkg.com/react-test-renderer@17.0.2/umd/
• scheduler: https://unpkg.com/scheduler@0.20.2/umd/