| X | ||
|---|---|---|
| Characters | 280 | 2,200 |
| Media | optional | a photo or video (required) |
| Hashtags | 1-2 hashtags, zero is fine | max 5 hashtags at the END of the caption |
| Links in body | suppress reach | fine |
| Needs platform approval | yes | yes |
X posts are frequently text-only. Instagram requires a photo or video on every post, so there is no direct equivalent — you have to attach media before this cross-post is even possible.
X caps at 280 characters, Instagram allows 2,200. Posting the short version verbatim wastes the room Instagram gives you to actually explain the thing.
X: 1-2 hashtags, zero is fine. Instagram: max 5 hashtags at the END of the caption. Carrying the tag block across is the single most obvious sign of an automated cross-post.
X penalises links in the body, so posts written for it park the URL elsewhere. On Instagram links in the body are fine — putting it back is free reach.
X is one hook and nothing else — opinionated, conversational, over in a breath. Instagram is built for short captions — under 100 characters is rewarded. 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": ["x", "instagram"],
"text": "Your post",
"per_platform": {
"x": { "text": "The X version" },
"instagram": { "text": "The Instagram 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: Instagram to X · all combinations · which APIs need approval
Most tools that do this bill per connected profile. What that actually costs once you add a second brand is worth reading first.