| Mastodon | ||
|---|---|---|
| Characters | 3,000 | 500 |
| Media | optional | optional |
| Hashtags | 3 hashtags (5 max) at the end | 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers |
| Links in body | suppress reach | fine |
| Needs platform approval | yes | no |
LinkedIn allows 3,000 characters; Mastodon caps at 500. A post written to LinkedIn's length gets truncated — usually mid-sentence — unless it is rewritten, not trimmed.
LinkedIn: 3 hashtags (5 max) at the end. Mastodon: 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers. Carrying the tag block across is the single most obvious sign of an automated cross-post.
LinkedIn penalises links in the body, so posts written for it park the URL elsewhere. On Mastodon links in the body are fine — putting it back is free reach.
LinkedIn is professional and first-person; the hook must fit in 210 characters. Mastodon is community-first; alt text on media is expected, not optional. 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.
curl -X POST https://postwire.io/api/post \
-H "Authorization: Bearer $POSTWIRE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"platforms": ["linkedin", "mastodon"],
"text": "Your post",
"per_platform": {
"linkedin": { "text": "The LinkedIn version" },
"mastodon": { "text": "The Mastodon 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.
Other pairs: Mastodon to LinkedIn · all combinations · which APIs need approval