React Strict Mode

Strict Mode helps find problems in development.

Usage

import { StrictMode } from 'react';

function App() {
  return (
    <StrictMode>
      <MyComponent />
    </StrictMode>
  );
}

What It Does

• Warns about deprecated APIs
• Detects unsafe lifecycles
• Warns about legacy string refs
• Detects unexpected side effects
• Ensures reusable state

Double Rendering

In development, renders components twice to catch bugs:

useEffect(() => {
  console.log('Effect runs');  // Runs twice in StrictMode
}, []);

Remember

• Only in development
• No visual output
• Helps catch bugs early
• Applies to children only

Next: Learn code splitting strategies!