Because an automatic crop with no subject information takes the middle. Slide a crop if you know yours is taken elsewhere.

Is 9:16 with bars what Instagram shows?

It is a generic allowance, not a measurement of any app. The bars are labelled unmeasured for that reason.

What size should a YouTube thumbnail be?

YouTube's own help page says 16:9, ideally 3840 × 2160, at least 640 pixels wide, JPG or PNG, and up to 2 MB when uploaded from a phone.

Reading

Crop-safe placement: what the crop check measures

The crop check under the stage says whether a mark survives the crops other people will apply. Here is exactly what it measures, what it assumes, and which numbers have a source behind them.

Open the placing toolBoth files stay on your device — we only draw one on top of the other.

The method

For each shape you tick, the check takes the largest rectangle of that shape that fits the photo, centred, and measures how far the mark's bounding box reaches outside it, in the photo's own pixels. Zero is a clear; anything else is the number of pixels a crop would cut off. The circle is measured exactly against the circle, corner by corner.

“Snap inside every selected crop” moves the mark into the rectangle all the ticked shapes share. If the mark is bigger than that rectangle, moving it cannot help, and the check says so with the size that would fit instead of moving it somewhere and calling it fixed.

The shapes

1:1, 4:5 and 9:16 are ticked when it opens. More shapes adds 16:9 (video thumbnails and banners), 3:4, 2:3, 1.91:1 (link previews) and a circle (profile pictures). These are generic shapes, not measurements of any named service.

Sliding a crop, and the bars over 9:16

A feed crop is not always taken from the middle, so each preview has a slider that moves its crop towards one end of the photo. The 9:16 shape can also keep clear of the bars a story or reel screen draws over the top and bottom of the frame. Those bars are a generic allowance — 14 per cent at the top and 20 at the bottom — and are labelled unmeasured wherever they appear, because no service publishes them.

What has a source

Of the destinations people ask about, only YouTube publishes its thumbnail rules: 16:9, recommended 3840 × 2160, at least 640 pixels wide, JPG or PNG, up to 2 MB on mobile (YouTube Help, “Add video thumbnails”, read 18 October 2026). Shorts thumbnails are 9:16, recommended 2160 × 3840, on the same page. Instagram's 4:5 portrait crop is widely documented by third parties, but we have not checked it against Meta's own help pages, so it is a common shape here, not a measured one.

A dated survey of named surfaces — what each crops, from which edge, under which interface — is planned. Until it exists, no verdict here is phrased as a promise about any platform.

In short

Measured: The mark's bounding box against each crop, in the photo's pixels.
Default shapes: 1:1, 4:5, 9:16 from the centre.
More shapes: 16:9, 3:4, 2:3, 1.91:1, circle.
Bars over 9:16: Generic 14% top, 20% bottom, unmeasured.

A person cropping by hand can take any part of the frame; no placement survives all of those.
The check uses the mark's bounding box, so a rotated mark is checked by its rotated corners' box.

Questions

Why from the centre?: Because an automatic crop with no subject information takes the middle. Slide a crop if you know yours is taken elsewhere.
Is 9:16 with bars what Instagram shows?: It is a generic allowance, not a measurement of any app. The bars are labelled unmeasured for that reason.
What size should a YouTube thumbnail be?: YouTube's own help page says 16:9, ideally 3840 × 2160, at least 640 pixels wide, JPG or PNG, and up to 2 MB when uploaded from a phone.