Mastodon is the decentralized social network that showed the world there’s another way to do social media. Created by Eugen Rochko in 2016, it’s built on the ActivityPub protocol and runs as a federation of independently operated servers (called instances) that can all talk to each other. Nobody owns Mastodon — it’s free, open-source software that anyone can host.
The platform saw massive growth in late 2022 when Elon Musk’s acquisition of Twitter drove waves of users looking for alternatives. Mastodon went from about 300,000 monthly active users to over 2.5 million in a matter of weeks. The interface looks familiar to Twitter users — short posts (called toots, later renamed to posts), boosts instead of retweets, and favorites instead of likes.
What makes Mastodon fundamentally different is its architecture. Each instance has its own rules, moderation policies, and community culture. Users on mastodon.social (the flagship instance) can follow and interact with users on any other Mastodon instance, or even other ActivityPub-compatible platforms like Pixelfed or PeerTube. This interoperability is part of what’s called the Fediverse.
Mastodon doesn’t have an algorithm pushing content, doesn’t show ads, and doesn’t track users for advertising. Timelines are chronological. There’s no quote-posting by default (a deliberate design choice to reduce pile-ons). Content warnings are a built-in feature that the community actively uses.
The trade-off is complexity. Choosing an instance, understanding federation, and finding people to follow all require more effort than signing up for a centralized service. Rochko has worked to simplify onboarding, but the learning curve remains Mastodon’s biggest barrier to mainstream adoption.
