React and react-router-dom operate entirely on the client side, so they don’t have the ability to set HTTP status codes like 404, which are a server-side concept. You can certainly display a “Not Found” page in React when a user tries to access a route that doesn’t exist, but the HTTP status code will still be 200 because the server successfully sent the HTML and JavaScript to the client. If you want to return a 404 status code, you’d need to handle that on the server side. For example, in Express.js, you could add a catch-all route handler after all your other routes that sends a 404 status. If you’re using server-side rendering or static site generation (like Next.js), you could potentially return a 404 status code along with a “Not Found” page. But with a purely client-side React app, it’s not possible.