| Mastodon | X | |
|---|---|---|
| Characters | 500 | 280 |
| Media | optional | optional |
| Hashtags | 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers | 1-2 hashtags, zero is fine |
| Links in body | fine | suppress reach |
| Needs platform approval | no | yes |
Mastodon allows 500 characters; X caps at 280. A post written to Mastodon's length gets truncated — usually mid-sentence — unless it is rewritten, not trimmed.
Mastodon: 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers. X: 1-2 hashtags, zero is fine. Carrying the tag block across is the single most obvious sign of an automated cross-post.
Links are fine on Mastodon. On X they cut distribution — the link belongs in a reply, not in the post.
You can post to Mastodon today with a credential you generate yourself. X gates posting behind a platform review — see our API approval notes for what that actually takes.
Mastodon is community-first; alt text on media is expected, not optional. X is one hook and nothing else — opinionated, conversational, over in a breath. 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": ["mastodon", "x"],
"text": "Your post",
"per_platform": {
"mastodon": { "text": "The Mastodon version" },
"x": { "text": "The X 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.
PostWire takes one idea and publishes a version written for each network — the right length, hashtags and format per platform. It also refuses posts that would fail, like a video network with no video, before they are queued.
Free for one brand — 30 posts a month, no card. Starter is $9/month for three brands and 300 posts. There is a REST API and an MCP server if you would rather automate it.
Start free — no card →Other pairs: X to Mastodon · all combinations · which APIs need approval
Picking a tool for this? We compared the ones with a public API side by side in the alternatives guide, prices included.