What is the character limit difference between Mastodon and Facebook?

Mastodon allows 500 characters and Facebook allows 2,000.

How do I post to Mastodon and Facebook at the same time?

With PostWire, one API call publishes to both: POST /api/post with platforms set to ["mastodon","facebook"]. Or one MCP tool call from an AI agent.

Works, with rewrites

Cross-posting Mastodon to Facebook: what actually breaks

You can, but not by copying the text across: 3 things change between Mastodon and Facebook, starting with you have 1,500 characters you are not using. Below is exactly what breaks and what to do instead.

Side by side

	Mastodon	Facebook
Characters	500	2,000
Media	optional	optional
Hashtags	2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers	1-3 hashtags
Links in body	fine	fine
Needs platform approval	no	yes

What changes, one by one

You have 1,500 characters you are not using

Mastodon caps at 500 characters, Facebook allows 2,000. Posting the short version verbatim wastes the room Facebook gives you to actually explain the thing.

The hashtag rules are not the same

Mastodon: 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers. Facebook: 1-3 hashtags. Carrying the tag block across is the single most obvious sign of an automated cross-post.

Facebook needs approval, Mastodon does not

You can post to Mastodon today with a credential you generate yourself. Facebook gates posting behind a platform review — see our API approval notes for what that actually takes.

Why copy-paste cross-posting underperforms

Mastodon is community-first; alt text on media is expected, not optional. Facebook is warm and community-toned; 40-80 characters peaks engagement. Those are different jobs, so the same words cannot do both well — and every algorithm here demotes text that obviously was not written for it. The fix is not to skip cross-posting; it is to send a native version to each network.

Publish to both in one call

curl -X POST https://postwire.io/api/post \
  -H "Authorization: Bearer $POSTWIRE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "platforms": ["mastodon", "facebook"],
    "text": "Your post",
    "per_platform": {
      "mastodon": { "text": "The Mastodon version" },
      "facebook": { "text": "The Facebook version" }
    }
  }'

PostWire's /api/generate writes those per-platform versions for you from a single prompt, respecting every limit in the table above. From an AI agent it is one MCP tool call.

Get an API key free →

Questions people actually ask

Can I cross-post from Mastodon to Facebook?: You can, but not by copying the text across: 3 things change between Mastodon and Facebook, starting with you have 1,500 characters you are not using. Below is exactly what breaks and what to do instead.
What is the character limit difference between Mastodon and Facebook?: Mastodon allows 500 characters and Facebook allows 2,000.
How do I post to Mastodon and Facebook at the same time?: With PostWire, one API call publishes to both: POST /api/post with platforms set to ["mastodon","facebook"]. Or one MCP tool call from an AI agent.

Other pairs: Facebook to Mastodon · all combinations · which APIs need approval