OpenGraph Sniffer MHL by Marcin Orlowski

A small browser extension that tells you at a glance whether the page you are looking at ships OpenGraph or Twitter Card metadata, and lets you grab these tags with one click, including page thumbnail.
Features:
- Shows an icon on the address bar whenever the page declares OpenGraph or Twitter Card tags.
- Allows you to see and copy out all the tags page uses, incl. thumbnail images.
- Automatically fetch the page in anonymous crawler mode (as i.e. Slack or Signal does) for complete tags set.