Mastodon review 2026: the open-source, decentralized social network. Learn how federation works, key features, pros, cons, and Twitter/X alternatives.
Mastodon is free, open-source software for running decentralized social networks, created by developer Eugen Rochko and publicly released in October 2016. Rather than a single company operating one platform, Mastodon lets anyone run their own server, or instance, with its own community rules, while still interoperating with other instances through the ActivityPub protocol.
This federated structure, often called the Fediverse, means Mastodon functions more like email than a traditional social network: users on different servers can follow and interact with each other, and no single entity controls the entire network.
Mastodon offers familiar social networking features, including posts (called toots or statuses), replies, boosts (similar to reposts), favorites, and direct messages, along with chronological, non-algorithmic timelines by default and granular content warnings.
Because each instance sets its own moderation policy, users can choose communities aligned with their interests or values, while cross-instance federation via ActivityPub still allows a global, interconnected timeline across the wider Fediverse, including compatible apps like Pixelfed and PeerTube.
Mastodon the software is free and open source, and joining most public instances, including the flagship mastodon.social, costs nothing. There are no subscription fees for using the core social network.
Running your own instance is free of software licensing costs, but administrators must cover their own hosting, storage, and moderation costs, which scale with the size of the community they host.
Mastodon is free, open-source software for running decentralized, federated social networks, created by Eugen Rochko and released in October 2016.
Yes, Mastodon is free and open source; joining most public instances costs nothing, though self-hosting a private instance requires paying for infrastructure.
Mastodon is decentralized, with independent servers called instances that interoperate via the ActivityPub protocol, rather than being run by a single company, and it uses chronological rather than algorithmic timelines.
Mastodon was created by German software developer Eugen Rochko, who began building it in 2016 and publicly released it in October of that year.
Mastodon has over 10.5 million registered accounts, though monthly active users are considerably smaller, estimated at roughly 750,000 to 1 million as of 2026.
The Fediverse is the broader network of interoperable, ActivityPub-based platforms that includes Mastodon along with apps like Pixelfed and PeerTube.