How can I count monthly active users?

Community Building Data & reporting
3

(For myself, I recently needed Monthly Active Users as a calibration of how “large” my forum is, for legal compliance reasons. I was able to read it from forum.example.com/about.json - I very much hope this remains available, and is not ‘decluttered’ as the about page was.)

Edit: for this meta forum, I see these stats in the about.json:

      "users_30_days": 1224,
      "active_users_30_days": 3259,
      "participating_users_30_days": 1031,
      "visitors_30_days": 6980,
      "eu_visitors_30_days": 1399,

I don’t know precisely what all of those mean.