The drop at the beginning of June is likely due to a change in the way we counted “Created an ID”.
We found we were counting automatically-updated IDs as “activity” for the “Active Users” stats. So for example, if user X added an ID in 2023 and never came back to iNat, and that ID was updated by the system due to a taxon change in June 2025, that updated ID being added to the observation would count as “activity” for the account. And the account would be considered an “active user”. So the number of active users in the count were higher than the number of people actively contributing to the site.
We added a change around the beginning of June that no longer considers those types of ID updates as “activity”, which likely accounts for the steep drop-off around that time. That jump at the end of May after a bit of a dip was what caught our eye and I believe it coincided with a taxon change or changes that affected a lot of IDs.