mastodon.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
The original server operated by the Mastodon gGmbH non-profit

Administered by:

Server stats:

360K
active users

Mastodon bumps up the active user count when a user logs on, including right after sign up. I’m not surprised the monthly active user number is coming down a bit, there’s no service out there that has 100% retention on new sign ups.