Misskey

Misskey is a decentralized, app-like microblogging server and social networking service for the Fediverse that uses the ActivityPub protocol. It is for Fediverse users who want an ActivityPub-based SNS. GNU social and Mastodon use ActivityPub too. Users can thus compare all three in the same protocol and social networking context. Misskey's main limitation is its narrow focus on microblogging through ActivityPub. It serves as a Fediverse server and SNS, not as a general-purpose program for unrelated tasks. People who want a different kind of program would need another option. For those focused on decentralized microblogging, Misskey shares both its Fediverse setting and its protocol with GNU social and Mastodon. That makes the comparison direct, but it does not turn Misskey into a broader tool.