Simple Update Protocol, or
SUP, was a protocol developed by
FriendFeed to simplify and speed up
RSS and
Atom. A few websites supported SUP for a while, meaning that updates from their services appeared in FriendFeed within seconds, until support was dropped, and eventually FriendFeed itself shutdown 2015-04-09.
[1]These sites include
Disqus,
Identi.ca,
reddit.