Mastodon is a free, open-source social network server software. It is essentially a micro-blogging system, very similar to Twitter, however, the network is decentralized in the sense that anyone can host and manage a Mastodon community, which are called "instances". Each Mastodon instance is independent but networked, and thousands of independent communities running Mastodon form a coherent network.
Comity integrates with Mastodon. You can connect any Mastodon account from any Mastodon instance to Comity and publish posts to these accounts from a single place.
Authorizing Mastodon accounts requires one extra step compared to the authorization of other social networks. You will be prompted with the screen below first, where you need to type your identifier, which is your username and the domain of the Mastodon instance in the following format: username@domain
Upon submitting the identifier, the process is as usual. You will be asked to log in your Mastodon instance account and authorize Comity.