Same instinct, different architecture. All three exist because people are tired of a handful of companies owning the social graph. But "decentralized" means something different in each case, and it's worth knowing which kind you're getting.
Mastodon runs on ActivityPub, an open protocol federating independently run servers called instances. You join a specific instance — @[email protected] — and while you can interact across the wider Fediverse, your account has historically lived on that one server. It's open source, non-profit, funded by donations, defaults to a chronological feed with no algorithm, and skews toward tech workers, journalists and privacy-conscious users.
Bluesky runs on AT Protocol, built by a team that spun out of Twitter specifically to make identity and posts genuinely portable — your account isn't tied to any one server, and your history moves with you if you switch providers. It's grown faster than Mastodon, is far easier to onboard into since there's no instance to choose, supports swappable custom algorithmic feeds, and is funded by venture capital rather than donations.
Where ATRIUM sits relative to both. Mastodon and Bluesky decentralize the network — no single company owns the whole graph, but you're still a member of somebody else's server or protocol instance. ATRIUM decentralizes ownership of the whole platform itself. You're not joining a community, you're operating one, with your own branding, your own storage provider, your own payment gateway, and 100% of the revenue, for a flat one cent per user per month rather than a revenue share.
The honest trade-off. Mastodon and Bluesky already have large, active audiences you can reach today. An ATRIUM network starts with zero members, because you're building your own community rather than joining an existing one. If your goal is to reach an existing audience, Mastodon or Bluesky get you there faster. If your goal is to own and monetize a community you build yourself, ATRIUM is solving a different problem than either.
Can they connect? This help center doesn't currently describe ActivityPub or AT Protocol bridging for ATRIUM networks. If cross-posting into the wider Fediverse matters to you, write to [email protected] and tell us — it helps us prioritize.