On Apr 2, 2015 10:05 PM, "Daniel Friesen" daniel@nadir-seen-fire.com wrote:
Twitter exclusively uses their proprietary Twitter cards markup ( <meta name="twitter:card" content="summary" /> ...) and requires you to validate and submit your site for approval before they'll display cards.
This isn't quite correct. They have their own thing, which allows you to give some Twitter-specific data, but attributes that are pretty standard (like thumbnail image) will fall back to open graph.
https://dev.twitter.com/cards/markup
You do have to submit a request, though, for cards to be shown. I think it's a pretty painless process, but I wasn't the one handling it when we implemented card support.
Reddit uses embed.ly, which is supposed to support a variety of Open Graph, oEmbed, etc...
Depending on what embedly tells us it can embed given certain conditions (for instance, the embed needs to support https if the requested page was https), we sometimes use embedly for thumbnails, and sometimes use our own scraper, with the code I linked to in my first email. It will currently pick up on opengraph tags, but if you decide to implement another standard we don't currently support, I will gladly build it in (pending some project scheduling, so perhaps not immediately).
From what I've seen, the various web-chat irc-replacements support open
graph as well, if they do any auto-link-embedding.