npm / react

react

What changed in react 19, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-17.

2 breaking7 security1 deprecations12 new APIs and options7 performance5 behavior and defaults2 tooling15 fixes and other

See which of these apply to your code, ranked, in your agent:

npx @unstale/cli init

react 1951 changes

Moves react-server-dom-webpack/*.unbundled to the private react-server-dom-unbundled package.
19.3.0release notes
Types were hardened in React Server Components, which may affect developer-written type usage.
19.2.6release notes

Adds nonce to rendered import maps.
19.3.0release notes
Added more DoS mitigations to Server Actions to improve application security.
19.2.4release notes
Hardened Server Components to improve application security.
19.2.4release notes
Added more DoS mitigations to Server Actions.
19.1.5release notes
Hardened Server Components against security threats.
19.1.5release notes
Added more DoS mitigations to Server Actions.
19.0.4release notes
Server Components were hardened against security threats.
19.0.4release notes

Development builds warn when a component appears to have been unblocked by calling use() conditionally.
19.3.0release notes

Adds an API for assigning transition types to React View Transition animations.
19.3.0release notes
Adds a react-dom API that marks a Suspense subtree as browser-only when used with use().
19.3.0release notes
Adds fetchPriority support for module resources.
19.3.0release notes
Adds refs to Fragment components to support composable platform behavior.
19.3.0release notes
Adds support for the maskType SVG prop.
19.3.0release notes
Adds support for the onFullscreenChange event.
19.3.0release notes
Adds support for the onFullscreenError event.
19.3.0release notes
Allows overriding request.timeOrigin through options.startTime.
19.3.0release notes
Adds an option to observe when a subtree defers rendering to the browser.
19.3.0release notes
Enables React integration with the Trusted Types API.
19.3.0release notes
Adds an option to allow partial streams in the Flight Client.
19.3.0release notes
Adds the ViewTransition component to power View Transition animations in React.
19.3.0release notes

Improves the transport protocol used by React Server Components.
19.1.10, 19.2.9, 19.3.1release notes release notes release notes
Avoids setting innerHTML when its value has not changed.
19.3.0release notes
Batches updates from resize events until the next frame.
19.3.0release notes
Performance improvements when decoding React Server Components.
19.0.8, 19.1.9, 19.2.8release notes release notes release notes
React Server Components received performance improvements that may improve application runtime behavior.
19.2.6release notes
React Server Components received performance improvements that may improve application runtime behavior.
19.1.7release notes
Performance improvements make React Server Components more efficient.
19.0.6release notes

Adds support for transporting Error.cause through Flight replies.
19.3.0release notes
Allows Server Components to render context providers from client modules.
19.3.0release notes
Includes submitter in submit events and uses the FormData submitter parameter.
19.3.0release notes
Transitions render independently, so a slow transition no longer holds up unrelated transitions.
19.3.0release notes
Transitions render independently instead of being entangled into one render.
19.3.0release notes

Types were hardened for React Server Components, improving type safety for developers using them.
19.1.7release notes
Type hardening improves the type surface for React Server Components.
19.0.6release notes

Adds support for transporting AggregateError.errors through Flight replies.
19.3.0release notes
Recognizes credentialless as a boolean iframe attribute and suggests its correct casing.
19.3.0release notes
Updates defaultValue handling for number inputs to match other input types.
19.3.0release notes
Fires onReset when forms are automatically reset.
19.3.0release notes
Forwards the nonce option when preloading modules.
19.3.0release notes
Fixed missing FormData entries in Server Actions.
19.0.7, 19.1.8, 19.2.7release notes release notes release notes
React Server Components add more cycle protections.
19.2.5release notes
Adds extra loop protection to React Server Functions.
19.2.3release notes
Promise cycles and toString behavior on Server Functions were patched.
19.0.2, 19.1.3, 19.2.2release notes release notes release notes
React Server Component fixes were brought to Server Actions.
19.2.1release notes
Adds extra loop protection to React Server Functions, helping prevent excessive or infinite execution loops.
19.1.4release notes
React Server Component fixes are now included in Server Actions.
19.1.2release notes
React Server Components add more cycle protections.
19.0.5release notes
React Server Functions add extra loop protection to prevent problematic execution loops.
19.0.3release notes
React Server Component fixes were brought to Server Actions.
19.0.1release notes