robots.txt

Place a robots.txt file in /app/ to tell search engine crawlers which URLs they can access on your site.

Alternatively, generate the file programmatically in robots.(js|ts).

robots.js is a special Route Handler that is cached by default unless it relies on a dynamic API or a dynamic configuration option.
robots.ts:
import type { MetadataRoute } from 'next'
 
export default function robots(): MetadataRoute.Robots {
  return {
    rules: [
      {
        userAgent: 'Googlebot',    // * for all agents
        allow: ['/'],
        disallow: '/private/',
      },
      {
        userAgent: ['Applebot', 'Bingbot'],
        disallow: ['/'],
      },
    ],
    sitemap: 'https://acme.com/sitemap.xml',
  }
}

robots.txt:
User-Agent: Googlebot
Allow: /
Disallow: /private/
User-Agent: Applebot
Disallow: /
User-Agent: Bingbot
Disallow: /
Sitemap: https://acme.com/sitemap.xml