Is the video itself being cropped?

Usually not. The frame is intact and the app is drawing its own controls over the top of it, which looks identical to cropping but has a different fix.

Does this differ between apps?

The exact heights differ, but every vertical feed claims the bottom of the frame and the right edge. Writing clear of both is what makes one clip safe everywhere.

Where should the words sit instead?

Above the interface band and roughly in the lower middle of the picture, which is where the eye already is. You can drag the position and see it live before anything is produced.

Why does it look fine in my editor?

An editor shows the clean frame. Nothing in it draws the buttons the app will add later, so the only honest check is the app itself.

Does a smaller size solve it?

It moves the problem rather than solving it. Text small enough to escape the buttons is usually too small to read while scrolling.

What happens when someone taps to expand the post text?

It covers more of the frame than usual, sometimes half of it. That is another reason nothing essential should sit low.

Does this differ on a tablet?

The controls are placed differently and the principle holds. The bottom and one edge are always claimed by the app rather than by you.

Why Subtitles Get Cut Off on Phones

How much of a vertical frame is actually usable?

Less than the file suggests. Roughly the bottom fifth carries the account name, the caption and the progress bar, and the right edge carries the action buttons. Text placed inside those areas is not cropped away, it is simply covered by the app that is playing it.

Which part of the frame each app claims

Exact heights differ between apps. Designing for the strictest case makes one clip safe on all of them.

Region	What sits there	Safe to use?
Bottom fifth	Account name, post text, progress bar	No, covered on every vertical feed
Right edge	Like, comment, share and profile buttons	No, a stack of controls sits there
Lower middle	Nothing, on most feeds	Yes, and it is where the eye already rests
Top band	Occasionally a back arrow or a label	Mostly, and it is where hook lines belong
Extreme edges	Varies with screen shape	Avoid anything essential there

Finding the safe area

Take a screenshot of a posted clip on each app you use and note where the interface sits. The area clear of all overlays is where text should live. Keep a margin from the top, bottom and sides.

Save the screenshots as reference.

Line width

Lines written to the full width of the frame lose their edges on rounded screens and behind side buttons. Keep lines shorter so they sit comfortably within the centre.

Shorter lines are also easier to read.

Why editors mislead

Editing software shows the full frame without any app interface. Text that looks well placed there can be covered on a phone. Always check on a real device.

Post privately to test if needed.

Different apps, one position

Apps place interface elements differently, but a position slightly above the lower middle usually works on all of them.

Test once, then reuse.

Readable on the screen it will be watched on

Open your own clip in the app, not the file. The file looks clean. The app is where the buttons appear, so that is where the problem is visible.
Keep words out of the bottom fifth. That band belongs to the interface on every vertical feed, so nothing you write there is reliably readable.
Shorten the line rather than shrinking the type. Smaller type is harder to read on the device where most people will watch it.

Make one clip and open it in the app before you decide. Nothing to pay for the first.

Questions people ask

Is the video itself being cropped?: Usually not. The frame is intact and the app is drawing its own controls over the top of it, which looks identical to cropping but has a different fix.
Does this differ between apps?: The exact heights differ, but every vertical feed claims the bottom of the frame and the right edge. Writing clear of both is what makes one clip safe everywhere.
Where should the words sit instead?: Above the interface band and roughly in the lower middle of the picture, which is where the eye already is. You can drag the position and see it live before anything is produced.
Why does it look fine in my editor?: An editor shows the clean frame. Nothing in it draws the buttons the app will add later, so the only honest check is the app itself.
Does a smaller size solve it?: It moves the problem rather than solving it. Text small enough to escape the buttons is usually too small to read while scrolling.
What happens when someone taps to expand the post text?: It covers more of the frame than usual, sometimes half of it. That is another reason nothing essential should sit low.
Does this differ on a tablet?: The controls are placed differently and the principle holds. The bottom and one edge are always claimed by the app rather than by you.