Find out now, not at publish time
Every platform has its own limit and none of them agree. The rail beside your caption now checks against each one while you write.
What's new
Live caption-length checking on the platform rail, channel by channel
A "Fix with AI" action on the too-long banner, so the caption gets shortened for you
The ad creative wizard holds the same limits the editor does, so you meet them at the step that sets them
Post titles run through the same cleaner as the caption body