Upgrade to React 19

React 19 is a recommended upgrade for most apps already on React 18. The risk is concentrated in removed legacy APIs (string refs, legacy context, function-component propTypes/defaultProps, findDOMNode) and test tooling.

Version upgradeDifficulty: moderateEffort: 0.5–3 days for a typical appmedium risk

Last verified May 20, 2026 · Updated May 22, 2026

React 19 is a recommended upgrade for apps already on React 18. Most breakage comes from removed legacy APIs and incompatible test tooling — not from rewriting your components. Budget half a day to three days depending on enzyme/string-ref usage.

Who should upgrade

Apps on React 18 wanting Actions, form hooks, and improved hydration error messages.
Libraries that want to drop forwardRef boilerplate.
Teams on React 16/17 should first reach React 18, then 19.

Who should wait

Apps with heavy enzyme test suites until those are migrated to React Testing Library.
Apps blocked by a critical third-party library without a React 19-compatible release.

What changed

Actions: async transitions with built-in pending/error state.
New hooks: useActionState, useFormStatus, useOptimistic, and use().
ref is a regular prop; forwardRef is being deprecated.
Removed: string refs, legacy context, function-component propTypes/defaultProps, findDOMNode, and the shallow renderer.
Improved hydration error diffs.

Breaking changes concentrate in legacy APIs

The upgrade rarely touches modern function components. It touches code using string refs, legacy context, findDOMNode, and propTypes/defaultProps on function components. Inspect for those first.

Recommended upgrade paths

Fast path for apps already on React 18

# 1. Bump React$ npm install react@19 react-dom@19# 2. Run the official migration codemod recipe$ npx codemod@latest react/19/migration-recipe# 3. Typecheck + test$ npm run typecheck && npm test -- --watch=false

Compatibility matrix

Concern	React 18	React 19
forwardRef	Required for ref forwarding	Optional — ref is a prop
propTypes (function comps)	Runtime-checked	Ignored / removed
String refs	Deprecated	Removed
Enzyme	Unsupported	Unsupported
Server Components	Experimental	Stable (framework-dependent)

Migration executionAI-assisted migration workflow

Upgrade this app to React 19. First inspect for removed APIs (string refs, legacy context, function-component propTypes/defaultProps, findDOMNode, shallow renderer). Then bump react/react-dom, run `npx codemod@latest react/19/migration-recipe`, fix the inspection findings, and resolve type errors. Run typecheck, lint, and tests after each step and report before continuing.

Safety: Incremental edits only. Pause for review after the codemod and after each API replacement.

PR review checklist

react and react-dom are on the same 19.x version
No string refs, legacy context, or findDOMNode remain
forwardRef wrappers were only removed where the codemod is safe
Tests no longer use the shallow renderer or enzyme
No new React console warnings in test output

Rollback strategy

Keep the version bump, codemod, and manual fixes in separate commits.
Revert to react@18 react-dom@18 and reinstall if a blocking third-party incompatibility appears.
Hold the upgrade behind a release branch until the full test suite is green.

Common errors

'X is not a function' after findDOMNode removal — switch to a ref.
Hydration mismatch warnings — see the fix-react-hydration-errors workflow.
Type errors on ref props after dropping forwardRef.

Official sources

Official docsReact v19react.devreliability 98%
Backs the breaking-change and migration-step claims.
GitHub releaseReact 19.0.0 releasefacebook/reactreliability 92%
Backs the breaking-change and migration-step claims.
Migration guideReact 19 Upgrade Guidereact.devreliability 98%
Backs the breaking-change and migration-step claims.

Frequently asked questions

Is React 19 a hard upgrade?

For modern React 18 apps it is usually straightforward — the official codemod handles most mechanical changes. The effort scales with how much legacy API surface (string refs, enzyme, findDOMNode) your codebase still uses.

Do I need to rewrite components to use Actions?

No. Actions and the new form hooks are opt-in. You can upgrade to React 19 without adopting them and migrate forms incrementally.