mastodonUnicode code points
Mastodon post limits and media specs
Every number below is the one our publishing engine enforces before a Mastodon post goes out, with the source it came from and the date we last read it.
Text[text]
| Max length | 500 Unicode code points |
|---|---|
| Counting | Counted in Unicode code points: one plain character is one, and a link costs its full length. |
Media
| Constraint | Images[image] | Video |
|---|---|---|
| Per post | 4 | 1 |
| Formats | .png, .jpg, .jpeg, .gif, .webp | .mp4 |
| Max size | not published | not published |
| Max length | - | - |
| We publish it | yes | not yet |
We publish text and images here; video and PDF documents we do not deliver to Mastodon yet. A PDF deck degrades here into up to 4 slide images.
Mentions
| Syntax | @user@instance |
|---|
Full @user@instance links natively.
The guidance our own agent carries for Mastodon, verbatim.
How our publisher handles it
The notes our publishing engine carries for Mastodon, verbatim - what our adapter does, not only what the platform allows.
- 500 is the mastodon.social default - self-hosted instances may differ.
Questions
- How long can a Mastodon post be?
- 500 characters. Counted in Unicode code points: one plain character is one, and a link costs its full length.
- How many images can one Mastodon post have?
- Up to 4: .png, .jpg, .jpeg, .gif, .webp.
- What video does Mastodon accept?
- 1 video per post: .mp4.
- How do you tag an account on Mastodon?
- Write @user@instance. Full @user@instance links natively.
Sources, verified 2026-07-14
Each citation names where the number came from. Anything we could not confirm in an official document is marked, because a number nobody will stand behind should look different from one that is.
- [text]docs.joinmastodon.org defaultdocs.joinmastodon.orgverified 2026-07-14
- [image]sameverified 2026-07-14