From 2,997 active users across all lemmy instances at the beginning of June, the number increased to 52,797 by June 30th. Source.
An active user on Lemmy is "someone who has posted or commented on our instance or community within the last given time frame.” Source. That means lurkers are not counted as active users. There are currently almost 200k total users spread across the top 10 non-bot lemmy instances.
We're really building something here!
EDIT: Looking for a lemmy app? Here's a whole list: https://lemmy.world/post/465785
I'm not sure it was all warm blooded. Active, warm blooded users are probably the real metric.
Using 'Active Users' as the metric of growth is much more reliable than the total user count since there have been rashes of instances started up just for spam accounts.
It even mentions this as a note on the fedidb site:
https://fedidb.org/current-events/threadiverse