React 19 Source Migration Patterns
Reference for every source-file migration required for React 19.
Quick Reference Table
| Pattern | Action | Reference |
|---|---|---|
ReactDOM.render(...) |
→ createRoot().render() |
See references/api-migrations.md |
ReactDOM.hydrate(...) |
→ hydrateRoot(...) |
See references/api-migrations.md |
unmountComponentAtNode |
→ root.unmount() |
Inline fix |
ReactDOM.findDOMNode |
→ direct ref | Inline fix |
forwardRef(...) wrapper |
→ ref as direct prop | See references/api-migrations.md |
Component.defaultProps = {} |
→ ES6 default params | See references/api-migrations.md |
useRef() no arg |
→ useRef(null) |
Inline fix add null |
| Legacy Context | → createContext |
→ api-migrations.md#legacy-context |
String refs this.refs.x |
→ createRef() |
→ api-migrations.md#string-refs |
import React from 'react' (unused) |
Remove | Only if no React. usage in file |
PropTypes Rule
Do not remove .propTypes assignments. The prop-types package still works as a standalone validator. React 19 only removes the built-in runtime checking from the React package the package itself remains valid.
Add this comment above any .propTypes block:
// NOTE: React 19 no longer runs propTypes validation at runtime.
// PropTypes kept for documentation and IDE tooling only.
Read the Reference
For full before/after code for each migration, read references/api-migrations.md. It contains the complete patterns including edge cases for forwardRef with useImperativeHandle, defaultProps null vs undefined behavior, and legacy context provider/consumer cross-file migrations.