Why your Mastodon server's character limit isn't 500

500 is the default, not the rule. Here is how Mastodon counts, which servers change it, and what happens when you post across several.

Mastodon's character limit is 500 — except when it is not. Unlike a centralised network, where one company sets one number, every Mastodon server chooses its own. 500 is what the software ships with, and plenty of admins raise it.

That is fine until you post to more than one server, or use a tool that assumes a single limit. Then it becomes the reason a post that looked fine gets rejected.

How Mastodon actually counts

Two rules make Mastodon more generous than a plain character count suggests, and both are worth knowing because they change how you write.

Every link counts as 23 characters. It does not matter whether the URL is 20 characters or 200 — it costs you 23. Shortening a link before posting to Mastodon achieves nothing except making it uglier and harder to trust.

The domain part of a mention does not count. Writing @someone@a-very-long-instance.example costs the same as @someone. Conversations across servers would be unusable otherwise.

So a post packed with links and mentions has far more room than any naive counter will tell you. If a tool is counting raw characters, it is under-reporting how much you can say.

The content warning is separate

The content warning field has its own allowance and does not eat into the post body. Which is a small kindness, and one reason CWs are used so freely on Mastodon compared to how content notes work elsewhere.

Servers that change the limit

Admins can raise the limit, and some do — a few substantially. There is no central list, but every server publishes its own numbers through its API, so you can look yours up in seconds. Know your own server's number, and treat 500 as the safe floor when posting anywhere else.

"If you post to one server, use its limit. If you post to several, write to 500 and you will never be surprised."

Most scheduling tools hold every Mastodon post to 500 rather than ask each server. PostDaily reads your server's own limit when you connect and checks it daily, so a post is held to what your server actually allows, and falls back to 500 only when a server doesn't say.

What happens if you go over

Your server rejects the post. It is not truncated, not posted partially, not queued — refused. If it happened through a scheduling tool, whether you find out depends entirely on whether that tool surfaces the error or swallows it, which is worth testing before you rely on one.

Writing longer

• Thread it. A reply chain is native to Mastodon and reads better than a wall of text anyway.
• Put the detail behind a link. A blog post with a link costs you 23 characters and gives readers the option.
• Use the content warning as a headline. A short CW plus a longer body is a well-established Mastodon pattern, not a workaround.

How to find your own server's limit

The reliable way is to look: open the compose box and start typing. The counter reflects your server's actual configured limit, whatever it is, and it is the only source that cannot be out of date.

Some servers also state it in their About page alongside the rules, which is worth checking if you are choosing where to join and long posts matter to you.

Why servers raise it, and why most do not

Admins who raise the limit usually do it for a community that writes essays — academic, literary, technical. Admins who leave it alone tend to argue that the constraint is what keeps timelines readable, and that people who want long-form should link to it.

Both positions are defensible and neither is going to win, which is precisely why the limit is a per-server setting rather than a platform decision. It is a small illustration of what federation actually means in practice: the software ships a default, and the person running each server decides whether to keep it.

A note on people reading you elsewhere

A post written on a server with a raised limit still federates to servers running the default. It does not get truncated — receiving servers display what they are sent — but it will look enormous in a timeline of 500-character posts.

Worth remembering if your server allows 5,000 and your audience is mostly elsewhere. The limit you write to is a courtesy question as much as a technical one.

If you want the same breakdown for every other network, there is a reference for that.