Google Play screenshot rules: 320-3840 px, no alpha, 2x ratio

Google Play's baseline screenshot rule is JPEG or 24-bit PNG (no alpha), a minimum dimension of 320 px, a maximum of 3840 px, and a long edge no more than twice the short edge. The custom-pixel limit on aspect ratio for ChatGPT Image 2.5 on Sume is 3:1, so it will allow shapes Play rejects: you have to enforce the 2:1 cap yourself.

Play's rules are from the Play Console page; the Sume limits are from Image models.

Where do Play and Sume limits overlap?

Play's maximum of 3840 matches the Sume maximum edge of 3840. The docs say, for ChatGPT Image 2.5, custom pixels need both edges to be multiples of 16, a maximum edge of 3840, an aspect ratio of at most 3:1, and 655,360 to 8,294,400 pixels. The table below sets the two rule sets side by side.

Does 24-bit PNG without alpha matter?

Yes, Play says JPEG or 24-bit PNG with no alpha. The Sume output_format field takes png, jpeg, webp, or svg, so request png or jpeg. Whether a given PNG carries an alpha channel is something to check on the file before you upload; the docs do not promise either way for ordinary outputs. Choose jpeg if you want to avoid the question.

What custom sizes are safe for both?

Pick edges that are multiples of 16, between 320 and 3840, with the long edge at most 2x the short. 1920x1080 is not a Sume custom size because 1080 is not a multiple of 16, but 3840x1920 and 1920x960 are, and so is 2880x1440. The aspect-ratio list in the docs (1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3, 4:5, 5:4, 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 9:21, 21:9) has no 8:5 and no 16:10. Use custom pixels instead.

What should I do?

Write a small check that rejects any file where the long edge is over twice the short edge, before uploading to Play. See also Google Play feature graphic size.