Setup Preview

2. Creates/Updates Files

vercel.json (All Frameworks)

{
  "headers": [
    {
      "source": "/(.*)",
      "has": [
        {
          "type": "host",
          "value": "{repo-name}-preview.jbcloud.app"
        }
      ],
      "headers": [
        {
          "key": "X-Robots-Tag",
          "value": "noindex, nofollow"
        }
      ]
    }
  ]
}

robots.txt Handler

Next.js (app/robots.ts):

import type { MetadataRoute } from 'next'

export default function robots(): MetadataRoute.Robots {
  const isProduction = process.env.VERCEL_GIT_COMMIT_REF === 'main'

  return isProduction
    ? { rules: { userAgent: '*', allow: '/' } }
    : { rules: { userAgent: '*', disallow: '/' } }
}

Astro (src/pages/robots.txt.ts):

import type { APIRoute } from 'astro';

export const GET: APIRoute = () => {
  const isProduction = process.env.VERCEL_GIT_COMMIT_REF === 'main';

  const robotsTxt = isProduction
    ? `User-agent: *\nAllow: /`
    : `User-agent: *\nDisallow: /`;

  return new Response(robotsTxt, {
    headers: { 'Content-Type': 'text/plain; charset=utf-8' },
  });
};

GitHub Actions Workflow (.github/workflows/preview.yml)