This site currently measures the concentration of user data for active users: in the Fediverse, this data is on servers (also known as instances); in the Atmosphere, it is on the PDSes that host users’ data repos. All PDSes run by the company Bluesky Social PBC are aggregated in this dataset, since they are under the control of a single entity. Similarly, mastodon.social and mastodon.online are combined as they are run by the same company.