React 18 provides a new method for managing roots. ReactDOM.render is deprecated and superseded by createRoot. To make the features of the new root API available to custom components, the <Scrivito.Extensions /> component should be initialized as shown in the example above.
If an app doesn’t use <Scrivito.Extensions />, custom components will be rendered with the deprecated ReactDOM.render method. In React 18 this produces a warning in the browser console: