Mastodon

Mastodon is open-source, decentralised microblogging. Instead of one company running one site, anyone can run a server - an instance - and those servers talk to each other over the ActivityPub protocol, so an account on one can follow, reply to, and boost accounts on any other. Collectively that network is the fediverse. The design decision that follows from this is the one that matters. There is no global algorithmic feed. Timelines are chronological, there is no advertising, and moderation policy is set by whoever runs your instance rather than by a single global trust-and-safety team. That makes moderation local and legible - you can read your server's rules and know who enforces them - and it means the experience varies by server, which is genuinely a trade-off rather than a pure win. Choosing an instance is a real onboarding cost that centralised platforms do not impose, and it remains the single biggest reason people bounce. For a founder or an organisation, the practical appeal is ownership. You can run your own instance on your own domain, verify your identity through a link on your own website, and keep an audience that no acquisition or policy change can take away. Account migration is built in: you can move to a different server and bring your followers with you, which structurally limits how much leverage any one operator holds over its users. The numbers are worth stating plainly rather than optimistically. Mastodon peaked at roughly 2.6 million monthly active users in November 2022, immediately after Twitter's acquisition, and has settled to somewhere between 750,000 and one million monthly actives in 2026, spread across thousands of instances. The wider fediverse has passed 11 million registered accounts with one to two million active. It is a real, durable network, and it is not a mass-market replacement for a large social platform. Governance changed in 2025 and 2026. Founder Eugen Rochko stepped down as CEO after ten years and the project completed a transition to a non-profit structure with more than 3 million euros in funding and a board that includes Twitter co-founder Biz Stone, explicitly to make the platform, in its own phrasing, hard for any single wealthy owner to capture. Funding comes from donations and grants rather than advertising. How it compares: Bluesky is the closest peer and is also protocol-based, but is easier to join and more centralised in practice; Threads is federating slowly and is owned by Meta; X is the incumbent it was built to be an alternative to. Mastodon's distinguishing claims are no ads, no algorithm, and no owner. It suits communities and individuals who want portability and local moderation. It is a poor fit for anyone whose goal is maximum reach.