next.js/examples/api-routes-cors/pages/index.tsx

export default function Index() {
  return (
    <p>
      To test the CORS route, open the console in a new tab on a different
      domain and make a POST / GET / OPTIONS request to <b>/api/cors</b>. Using
      a different method from those mentioned will be blocked by CORS
    </p>
  );
}