Mark Zuckerburg announced via a Facebook post that the company recently had 1 billion people use Facebook in a single day. It’s an impressive feat when you consider that’s about 1 in 7 people on the entire planet.
I, like many people, wanted to know how they were counting active users in this case. I didn’t find anything authoritative, but this thread on Hacker News had a few details from current and former Facebook employees. Basically that number seems to include users who viewed their logged-in account on web or mobile, and anybody who posted a like or comment on third-party content and sites. However you count them, engineering and supporting a platform that can support those kinds of numbers is an amazing feat indeed.