@marqle Yes, it is compatible because it uses the ActivityPub protocol under the hood, which is what makes Mastodon's federation work :).

There are also many other projects compatible with Mastodon: Pixelfed, Misskey, etc. All these applications are referred to as "the fediverse", so you can search for that if you're interested in learning more.

Personally I've only had experience with Mastodon, though.