Mastodon Server (Instance)

A Mastodon server (people also call it an instance) is one website running the Mastodon software. Mastodon's documentation compares picking one to picking an email provider. The server you sign up on hosts your account, your profile and your home feed. Servers talk to each other, so you can follow people on any other server and they can follow you. Together with other software that speaks the same protocol, they make up the fediverse.

Your Address and Your Server

Mastodon's documentation explains that a username has two parts, the local username and the domain of the server, just like an email address. For an account named alice on example.com:

How you share it	Works for people on other servers?
@alice	No, it leaves out the server
@alice@example.com	Yes
https://example.com/@alice	Yes, Mastodon's search finds a profile link too

People on your own server can address you without the domain. Share the full address with everyone else, or they won't find you as easily. The same username can belong to different people on different servers, the way alice@outlook.com and alice@gmail.com can.

What Each Server Decides

• Who can join. A server's admins pick one of three signup modes: open signups, invites only, or approval by a moderator.
• Its rules. Each server has its own policies and moderation. Servers listed on joinmastodon.org agree to the Mastodon Server Covenant, which asks them to moderate against hate speech, take daily backups, have at least one emergency admin and give at least 3 months' notice before shutting down.
• Its limits. A post can have 500 characters on a default server, and each server reports its own maximum in its instance settings (max_characters), along with how many media attachments a post can have and how many characters each link counts as.

Moving to Another Server

If your server shuts down or stops suiting you, Mastodon lets you move your account. You create an account on another server, export the list of people you follow from the old one and import it into the new one, link the two accounts with an alias, then redirect the old account. Your followers are switched to follow the new account automatically. After the move you can no longer use the old account, and Mastodon can't import your old posts or media, although you can download an archive of them.

Example

An illustrative case (the person and the servers are made up): Alice signs up on example.social, a server that allows 500 characters per post. Her address is @alice@example.social. A year later she moves to writers.example, which allows more. Her followers move with her, and her new address is @alice@writers.example.

In Postopus

When you connect Mastodon to Postopus, you type the server you sign in at, such as mastodon.social, or your full handle. You sign in on that server and approve Postopus there. The editor then counts your posts against that server's own character limit.

Sources

Checked on October 27, 2026.

• Mastodon documentation, Signing up for an account: choosing a server like an email provider, signup modes, the username and domain table, the same username on different servers.
• Mastodon documentation, What is Mastodon?: servers, federation and the Mastodon Server Covenant.
• Mastodon documentation, Posting to your profile: the default limit of 500 characters.
• Mastodon documentation, Instance: configuration.statuses.max_characters, max_media_attachments and characters_reserved_per_url.
• Mastodon documentation, Moving or leaving accounts: the steps to move, followers moving with you, and post archives.

Last reviewed: October 27, 2026