Deprecation notice: ReactDOM.render is no longer supported in React 18

I get this error every time I create a new React app:

> Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot

How can I fix it?

I created my React app using:

npx create-react-app my-app

In your file index.js, change to:

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

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

reportWebVitals();

React 18 shipped March 29th, 2022. ReactDOM.render has been deprecated in React 18 and currently issues a warning and runs in a compatible mode.

Deprecations

Deprecations

• react-dom: ReactDOM.render has been deprecated. Using it will warn and run your app in React 17 mode.
• react-dom: ReactDOM.hydrate has been deprecated. Using it will warn and run your app in React 17 mode.
• react-dom: ReactDOM.unmountComponentAtNode has been deprecated.
• react-dom: ReactDOM.renderSubtreeIntoContainer has been deprecated.
• react-dom/server: ReactDOMServer.renderToNodeStream has been deprecated.

To resolve it, you can either revert to a previous version of React or update your index.js file to align with the React 18 syntax.

Example:

import { StrictMode } from "react";
import { createRoot } from "react-dom/client";

import App from "./App";

const rootElement = document.getElementById("root");
const root = createRoot(rootElement);

root.render(
  <StrictMode>
    <App />
  </StrictMode>
);

Before

import { render } from 'react-dom';
const container = document.getElementById('app');
render(<App tab="home" />, container);

After

import { createRoot } from 'react-dom/client';
const container = document.getElementById('app');
const root = createRoot(container);
root.render(<App tab="home" />);

Before in your index.js file:

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);


reportWebVitals();

Change it like below into your index.js file:

import React from 'react';

import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

import { createRoot } from 'react-dom/client';
const container = document.getElementById('root');
const root = createRoot(container);
root.render(<React.StrictMode>
  <App />
</React.StrictMode>);


reportWebVitals();

As you said, you created your React app using: npx create-react-app my-app.

• Your index.js must look like this after the command executes.

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);

reportWebVitals();

• Your code after edits mentioned in the console

import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

const container = document.getElementById('root');
const root = ReactDOM.createRoot(container);
root.render(<App />);

reportWebVitals();

As your error states, ReactDOM.render is no longer supported. So use the new createRoot.

As you can see from the code below, (which was pulled from the documentation) all you have to do is replace ReactDOM.render with createRoot.

// Before
import { render } from 'react-dom';
const container = document.getElementById('app');
render(<App tab="home" />, container);

// After
import { createRoot } from 'react-dom/client';
const container = document.getElementById('app');
const root = createRoot(container);
root.render(<App tab="home" />);

To provide more or less an equivalent to prior versions of React, I use this slightly condensed version of the above, still surrounding the <App> with the <React.StrictMode>.

Another reason I condense this is I never need access to a root variable, as the result, chaining statements together, and the whole file is just five lines of code:

import React from 'react';
import ReactDOM from "react-dom/client";

import './index.css';
import App from './App';

    ReactDOM.createRoot(document.querySelector("#root")).render(<React.StrictMode><App /></React.StrictMode>);

(P.S.: Don't forget if you need the webvitals functionality to also add to the above code)

If your application is using React-Router, then the following code will work fine:

import { createRoot } from "react-dom/client";
const container = document.getElementById("root");
const root = createRoot(container);
root.render(
  <BrowserRouter>
    <App />
  </BrowserRouter>
);

It will work perfectly (with react-router).

In your index.js file:

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

Use this before React version 18

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

Use this in React version 18

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

This should do it:

import React from 'react';
import {createRoot}  from 'react-dom/client';
import App from './App';

const root = createRoot(document.getElementById("root"))
root.render
  (
    <App />
  )

Instead of:

import ReactDOM from 'react-dom'
ReactDom.render(<h1>Your App</h1>, document.getElementById('root'))

Use:

import { createRoot } from 'react-dom/client'
createRoot(document.getElementById('root')).render(<h1>Your App</h1>)

More details here