As you write, each selected channel shows a preview laid out the way that platform will render it. It is the closest thing to seeing the post before your customers do.
What to check on each
| Platform | Look for |
|---|---|
| Where the text gets cut off behind "see more" — the first line has to carry the post. | |
| The crop. Square images are safest; check nothing important is at the edge. | |
| Tone as much as layout. It should read like something a professional audience would share. | |
| Whether it reads as useful information about the business rather than as an advert. |
The preview is a guide, not a guarantee
Platforms change their own layouts constantly, and a phone renders differently from a desktop. The preview catches the big problems — a truncated first line, a badly cropped image, an empty channel — which is most of them.
THE FIRST LINE IS THE WHOLE POST
On every platform, most people only ever read the first line. If the preview shows your point arriving in sentence four, rewrite it.