Custom 404 page is present and helpful

The default framework 404 page exposes the framework name, version, and sometimes internal routing details — information an attacker uses to target known vulnerabilities (CWE-756). Beyond security, every user who hits a 404 without navigation options bounces permanently. A custom 404 page with a link back to the homepage recovers a portion of those users who arrived at a broken or moved URL, directly reducing churn from mislinked campaigns, renamed routes, and user typos.

Create app/not-found.tsx in Next.js App Router (or pages/404.tsx in Pages Router) with a clear message and a link back to the homepage.

// app/not-found.tsx
import Link from 'next/link'

export default function NotFound() {
  return (
    <main>
      <h1>Page Not Found</h1>
      <p>This page doesn't exist or has been moved.</p>
      <Link href="/">Return home</Link>
    </main>
  )
}

Include your site's normal navigation header so users can recover without the back button. Optionally add links to popular sections or a search bar. The page should match your brand styling — a bare white error screen signals a broken product.