From the checkup catalog
The launch-day checklist
Social tags, a real 404, robots, sitemap, legal pages, and Core Web Vitals when PageSpeed answers.
People check these every time they ship, then forget them. The launch meter looks for a viewport, a favicon, Open Graph title and image, a 404 that is actually a 404, robots.txt, a sitemap, and links to privacy and terms.
It also samples a few same-site links and times the first byte. If the URL is public and PageSpeed Insights answers, LCP, CLS, and INP replace the guess. Localhost keeps the timing checklist because Google cannot see your laptop.
The meter is separate from the A–F security grade. An app can be fast and still be leaking a key.