The full spec table
Safe zones: where your text can actually live
TikTok's interface covers more of the frame than most people realise. Keep faces, captions and calls to action inside the central area, away from the top bar of roughly 120 pixels, the action column down the right hand side, and the caption block of roughly 250 pixels along the bottom. Text that drifts into those areas gets buried under buttons and usernames.
The mistakes that get videos rejected
Three problems cause most failed TikTok publishes: a file over the size limit for the upload route being used, a codec TikTok's encoder dislikes (H.265 works on newer builds but compresses harder and can muddy fast motion), and audio flagged for licensing. If your post is going out through a scheduler, the file also has to pass the platform's API checks, which is exactly what a pre flight check catches before the publish time arrives rather than after it has passed.
One export for every platform?
Mostly, yes. A single 1080 by 1920 H.264 MP4 at 30fps under 250MB plays cleanly on TikTok, Instagram Reels and YouTube Shorts. The catch is duration: anything over 60 seconds is risky for Shorts recommendations and anything over 3 minutes stops being recommended to new audiences on Reels. The safe zones also differ, so captions positioned for TikTok can sit under Instagram's interface. Our five platform cheat sheet covers the differences in one table.