What is Mastodon?

Welcome to the Mastodon documentation!

What is a microblog?

Similar to how blogging is the act of publishing updates to a website, microblogging is the act of publishing small updates to a stream of updates on your profile. You can publish text posts and optionally attach media such as pictures, audio, video, or polls. Mastodon lets you follow friends and discover new ones.

What is federation?

Federation is a form of decentralization. Instead of a single central service that all people use, there are multiple services, that any number of people can use.

Grade of centralization	Examples
Centralized	Twitter, Facebook, Instagram
Federated	Email, XMPP, phone networks, physical mail
Distributed	BitTorrent, IPFS, Scuttlebutt

A Mastodon website can operate alone. Just like a traditional website, people sign up on it, post messages, upload pictures and talk to each other. Unlike a traditional website, Mastodon websites can interoperate, letting their users communicate with each other; just like you can send an email from your Gmail account to someone from Outlook, Fastmail, Protonmail, or any other email provider, as long as you know their email address, you can mention or message anyone on any website using their address.

From left to right: Centralized, Federated, Distributed

What is ActivityPub?

Mastodon uses a standardized, open protocol to implement federation. It is called ActivityPub. Any software that likewise implements federation via ActivityPub can seamlessly communicate with Mastodon, just like Mastodon websites communicate with one another.

The fediverse (“federated universe”) is the name for all websites that can communicate with each other over ActivityPub and the World Wide Web. That includes all Mastodon servers, but also other implementations:

Pleroma, a modular microblogging engine,
Pixelfed, federated image sharing platform, which lets you share and consume media posts,
Misskey, which includes microblogging alongside a customizable dashboard,
PeerTube, which lets you upload videos to channels,
Plume, which lets you publish longer-form articles,
and many more, including individual and personal websites!

The fediverse does not have its own brand, so you might more often hear “follow me on Mastodon” than “follow me on the fediverse”, but technically the latter is more correct.

Practical implications

Choice of service provider and policy

Because Mastodon is just software that can be used to power any website, potential users of Mastodon have the option of choosing a service provider from already-existing Mastodon websites, or to create their own Mastodon website if they wish. The Mastodon project maintains a list of recommended service providers at joinmastodon.org, sortable by category and/or language. Some websites may have moderation policies that go beyond this, such as requiring the use of certain tags on potentially sensitive content, and some websites may have more relaxed moderation policies, but websites listed in the picker all agree to adopt the Mastodon Server Covenant, meaning that they pledge to actively moderate against hate speech, to take daily backups, to have at least one emergency admin, and to provide at least 3 months advance notice in case of shutdown.

Maintaining communities that feel safe for all of its members is not easy. Mastodon provides a lot of foundational framework and tools for doing it, and shifts the power to effect change from one commercial entity to the communities themselves.
– Eugen Rochko, Jul 6 2018, “Cage the Mastodon”

A centralized social media platform has a hierarchical structure where rules and their enforcement, as well as the development and direction of the platform, are decided by the CEO […] A decentralized network deliberately relinquishes control of the platform owner, by essentially not having one.
– Eugen Rochko, Dec 30 2018, “Why does decentralization matter?”

Funding and monetization

Mastodon websites are operated by different people or organizations completely independently. Mastodon does not implement any monetization strategies in the software.

Some server operators choose to offer paid accounts, some server operators are companies who can utilize their existing infrastructure, some server operators rely on crowdfunding from their users via Patreon and similar services, and some server operators are just paying out-of-pocket for a personal server for themselves and maybe some friends. So if you want to support the server hosting your account, check if it offers a way to donate.

Mastodon development is likewise crowdfunded via Patreon and via OpenCollective. No venture capital is involved.

In my opinion, “instant, public, global messaging and conversation” should, in fact, be global. Distributed between independent organizations and actors who can self-govern. A public utility, without incentives to exploit the conversations for profit.
– Eugen Rochko, Mar 3 2018, “Twitter is not a public utility”

Interoperability between different software

In practical terms: Imagine if you could follow an Instagram user from your Twitter account and comment on their photos without leaving your account. If Twitter and Instagram were federated services that used the same protocol, that would be possible. With a Mastodon account, you can communicate with any other compatible website, even if it is not running on Mastodon. All that is necessary is that the software support the same subset of the ActivityPub protocol that allows for creating and interacting with status updates. To find out more about the technical specifications required to interoperate with Mastodon, see ActivityPub, WebFinger, and Security. To read more about what ActivityPub allows us to do, see Why ActivityPub is the future.

All of these platforms are different and they focus on different needs. And yet, the foundation is all the same: people subscribing to receive posts from other people. And so, they are all compatible.
– Eugen Rochko, Jun 27 2018, “Why ActivityPub is the future”

Free/libre software

Unlike proprietary services, anyone has the complete freedom to run, examine, inspect, copy, modify, distribute, and reuse the Mastodon source code, provided they guarantee the same freedoms for any derivative work. Just like how users of Mastodon can choose their service provider, you as an individual are free to contribute features to Mastodon or publish a modified version of Mastodon that includes different features. These modified versions, also known as software forks, are required to also uphold the same freedoms as the original Mastodon project. For example, glitch-soc is a software distribution that adds various experimental features. Many individual forks exist as well, perhaps themed slightly differently or including small modifications to the codebase. Because Mastodon is libre software that respects your freedom, personalizations like this are not only allowed but encouraged.

The ultimate power is in giving people the ability to create their own spaces, their own communities, to modify the software as they see fit, but without sacrificing the ability of people from different communities to interact with each other.
– Eugen Rochko, Feb 20 2017, “The power to build communities: A response to Mark Zuckerberg”

Decentralization is biodiversity of the digital world, the hallmark of a healthy ecosystem. A decentralized network like the fediverse allows different user interfaces, different software, different forms of government to co-exist and cooperate.
– Eugen Rochko, Dec 30 2018, “Why does decentralization matter?”