Platforms — Mastodon
Schedule Mastodon posts
Connect any Mastodon instance — postfast registers itself with the server on first connect — and schedule posts and threads to it.
Mastodon is not one service, and postfast treats it that way
Mastodon is software that thousands of servers run, and each server issues its own client credentials. There is no developer portal to register in once.
postfast registers an application with your instance the first time anybody connects to it, then reuses that registration for everyone else on the same server — one app per instance, exactly as Mastodon intends, rather than an abandoned registration on somebody else’s server for every workspace that ever tried.
That also means the character limit on this page is a default rather than a promise. 500 is what Mastodon ships with; plenty of instances run 1,000 or more and a few run less, and the instance itself has the final say. So the character rule on Mastodon is a warning rather than a block: postfast tells you that you are over the common default and lets your server decide.
What Mastodon accepts in one post
Read from the same capability table the composer warns from and the publisher builds payloads from. postfast's own bound of 5,000 characters and 4 media items applies on top, whichever is tighter.
- Characters
- 500 per post.
- Media items
- 4 per post on Mastodon's side; postfast accepts 4.
- Media required
- No. A text-only post publishes fine.
- Threads
- Native. Mastodon sets no limit of its own; postfast accepts up to 25 replies in one composed thread.
- Cost per post
- Nothing. The platform charges no API fee for publishing.
- Scheduling
- postfast holds the post and hands it over at the moment it is due, so a post can be scheduled a minute out or a year out.
How connecting works
- You give it your instance. Type the host you are on. postfast normalises it, registers with it if it has not met it before, and sends you there to approve.
- Per-instance OAuth. You approve on your own server’s consent screen. postfast never sees a password, and your instance can revoke the app at any time.
- Credentials are sealed at rest. The client secret your instance issues is treated as secret material in exactly the same way tokens are: encrypted under the application secret and opened only in memory to sign an exchange.
- Profile links carry the instance. A Mastodon profile lives at your own server, so postfast builds the link from the instance and the handle together rather than assuming one host for everybody.
What you get
Native threads
A status replying to your own status chains, so a composed thread publishes as a real thread on Mastodon.
Any instance, including your own
Self-hosted, niche, or one of the large public servers — the connection path is identical.
Free per post
Mastodon charges no API fee, and postfast meters nothing here.
A warning, not a veto
Over 500 characters is a caution rather than a refusal, because your instance sets the real limit and postfast will not overrule it from a static table.
Common questions
- Which Mastodon instances does postfast support?
- All of them. postfast registers an application with whichever instance you name the first time somebody connects to it, so no server has to be added to a list first.
- My instance allows 1,000 characters. Why does postfast warn at 500?
- 500 is Mastodon’s default, and it is what a static table can honestly claim. Because your instance may allow more or less, the rule is a warning rather than a block — you can schedule the post and your server decides.
- Does postfast support Mastodon threads?
- Yes. Self-replies chain natively, and a thread is published in order and resumed rather than restarted if a part fails.
Scheduling to Mastodon, and six other networks
postfast is pre-launch. Join the waitlist and you will hear from us when early access opens.