Mastodon

Mastodon is the most widely used implementation of ActivityPub, the open protocol that underlies the federated social web — the "Fediverse." Founded by Eugen Rochko in 2016, the project builds on the idea that social networking infrastructure should not be owned by a single company: instead of one platform, Mastodon is a network of thousands of independently operated servers called instances, each run by different administrators, each with its own community rules, and each capable of communicating with the others. A user on mastodon.social can follow and interact with users on infosec.exchange, fosstodon.org, or any other Mastodon instance through federation.

The technical architecture means that "Mastodon" is not a single service with a single status — it is a protocol and a reference implementation that runs on thousands of independent servers globally. Mastodon.social, the flagship instance run by Mastodon gGmbH, is the largest single instance and the one most often treated as a proxy for the health of Mastodon broadly. Individual instances can be down while the rest of the network continues operating. Federation between instances can degrade — where posts from one instance stop appearing in the timelines of followers on another — when the job queues that handle ActivityPub delivery back up or fail. The Mastodon web interface, iOS apps (official and third-party), and Android apps connect to specific instance servers, not to a central Mastodon infrastructure.

Mastodon service problems surface differently from centralised platforms. Instance downtime affects all users of that specific server — the web interface returns 502 or 503 errors, apps fail to load the home timeline, and notifications stop delivering. Federation delivery failures cause a more subtle problem: posts appear on the author's instance normally but fail to appear in followers' timelines on other instances, because the ActivityPub job that should deliver the post to remote instances fails silently or backs up. Media upload failures occur when the instance's object storage backend — often Wasabi, Backblaze, or S3 — has connectivity issues, preventing images and videos from attaching to posts. Full-text search failures affect instances running Elasticsearch or Meilisearch when those services are unavailable.

Outage.gg tracks Mastodon instance status using real-time community reports from users across major instances. If your Mastodon server is down, federation is broken, or posts are not delivering to followers, the live status page shows current impact from the Fediverse community.