| YouTube | ||
|---|---|---|
| Characters | 5,000 | 2,000 |
| Media | a video (required) | optional |
| Hashtags | 3-5 hashtags in the description, never more than 15 total | 1-3 hashtags |
| Links in body | fine | fine |
| Needs platform approval | yes | yes |
YouTube allows 5,000 characters; Facebook caps at 2,000. A post written to YouTube's length gets truncated — usually mid-sentence — unless it is rewritten, not trimmed.
YouTube: 3-5 hashtags in the description, never more than 15 total. Facebook: 1-3 hashtags. Carrying the tag block across is the single most obvious sign of an automated cross-post.
YouTube is a search engine: the title carries the keyword in the first 40 characters. 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.
curl -X POST https://postwire.io/api/post \
-H "Authorization: Bearer $POSTWIRE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"platforms": ["youtube", "facebook"],
"text": "Your post",
"per_platform": {
"youtube": { "text": "The YouTube 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.
Other pairs: Facebook to YouTube · all combinations · which APIs need approval