When Facebook says it has 1.55 billion monthly active users, the first thought you may have is holy hell, that’s an insane amount of users. In which case you’d be right.

The second thought you may have is well, what do they mean by user?

Now, what Facebook means by “user” is anyone who logged on to Facebook (via app or desktop) or Messenger directly. This wasn’t always the case.

Josh Constine at TechCrunch spotted a change in Facebook’s 10-Q update to its SEC filing that makes its 1.55 billion MAU number even more impressive.

Before, Facebook could technically count people to used Facebook to log in via third-party apps as “users”, even if they were a small part of the total pie.

But now that’s not the case.

Previously, Facebook said:

We define a monthly active user as a registered Facebook user who logged in and visited Facebook through our website or a mobile device, used our Messenger app (and is also a registered Facebook user), or took an action to share content or activity with his or her Facebook friends or connections via a third-party website or application that is integrated with Facebook, in the last 30 days as of the date of measurement.

And here’s what it says now:

We define a monthly active user as a registered Facebook user who logged in and visited Facebook through our website or a mobile device, or used our Messenger app (and is also a registered Facebook user), in the last 30 days as of the date of measurement.

Facebook is just massive. The whole Facebook empire. Facebook proper leads the way with 1.55 billion MAUs, but WhatsApp isn’t far behind with 900 million. Messenger alone has 700 million, and Instagram topped 400 million.

If you’re reading this, it’s highly unlikely that you’re not inside Facebook’s garden.