not-found.jsThe not-found file is used to render UI when the notFound function is thrown within a route segment. Along with serving a custom UI, Next.js will also return a 404 HTTP status code.
app/blog/not-found.tsx import Link from 'next/link'
 
export default function NotFound() {
  return (
    <div>
      <h2>Not Found</h2>
      <p>Could not find requested resource</p>
      <p>
        View <Link href="/blog">all posts</Link>
      </p>
    </div>
  )
}
Good to know: In addition to catching expected notFound() errors, the root app/not-found.js file also handles any unmatched URLs for your whole application. This means users that visit a URL that is not handled by your app will be shown the UI exported by the app/not-found.js file.
Props