What Is React Strict Mode? Complete Example Tutorial Guide

What Is React Strict Mode?

React Strict Mode is a tool for highlighting potential problems in an application.
It does not render any visible UI, but it activates additional checks and warnings for development mode only.

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Using Strict Mode

import React from "react";
import ReactDOM from "react-dom/client";
import App from "./App";

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>
);

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Key Features

• Identifies unsafe lifecycle methods
• Detects legacy string ref usage
• Warns about deprecated findDOMNode usage
• Helps detect unexpected side effects

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Example: Wrapping Components

function Child() {
  return <h2>Hello Strict Mode</h2>;
}

function App() {
  return (
    <React.StrictMode>
      <Child />
    </React.StrictMode>
  );
}

✅ React will double-invoke some functions in development to check for side effects.

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Conclusion

React Strict Mode is a development tool that helps catch potential issues early and ensures your app is future-proof.

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Citations

https://savanka.com/category/learn/react/
https://www.w3schools.com/REACT/DEFAULT.ASP