The notFound function allows you to render the not-found file within a route segment as well as inject a <meta name="robots" content="noindex" /> tag for search engines.

notFound()

Invoking the notFound() function throws a NEXT_HTTP_ERROR_FALLBACK;404 error and terminates rendering of the route segment in which it was thrown. Specifying a not-found file allows you to gracefully handle such errors by rendering a Not Found UI within the segment.

filename="app/user//page.js"

async function fetchUser(id) {
  const res = await fetch('https://...')
  if (!res.ok) return undefined
  return res.json()
}

export default async function Profile({ params }) {
  const { id } = await params
  const user = await fetchUser(id)

  if (!user) {
    notFound()
  }

  // ...
}

Good to know: notFound() does not require you to use return notFound() due to using the TypeScript never type.

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