What is Error 37?

I keep seeing people talking about this error.

There are even some memes already talking about "Error 37"

What is it and where does it come from ?

Error 37 is "Servers are Busy", please try again later. It starts popping up when too many people try to log onto the Diablo 3 servers at once.

It's notable because Blizzard specifically warned users that they might run into it at launch, and told them to ignore it and try again.

Bottom line is that the problem is not with your PC or your internet connection, but an error on Blizzard's end.

It's a generic error that indicates that there's no server availiable on the other end, and thus, you can't log in to play Diablo 3.

Error 37 is basically a "Server is busy" error which was causing people to not be able to log into the game early Tuesday morning, and obviously whenever servers get bogged down.