Social preview & crawler emulator
Requests your page with a crawler’s User-Agent and shows the metadata that came back — title, canonical, robots directives, Open Graph and Twitter card tags.
Why the User-Agent matters
Plenty of sites serve different markup to crawlers than to browsers — sometimes deliberately, often as an accident of a CDN rule, a bot-protection product, or a framework that only renders metadata for requests it considers real. Viewing source in your browser cannot show you that difference. Asking as Facebook can.
An emulation, not a reproduction
This sends the crawler’s User-Agent and reports the response. It is not Facebook: each platform applies its own caching, rendering and allow-list rules that no third party can reproduce. What it does show is what your server returned, which is where most broken previews actually originate.