App Store screenshot size (1290×2796) and AI images

Apple lists 1290×2796 pixels (portrait) as one accepted App Store screenshot size for 6.9-inch iPhone displays. Sume's ChatGPT Image 2.5 cannot output that exact size, because 1290 is not a multiple of 16. Generate the same shape at a size that passes, such as 560×1216, then resize it to the size Apple lists in your own editor.

Apple's numbers are quoted from Screenshot specifications, which can change; Sume's rules come from the Image API docs. Both were read 2026-09-29.

What sizes does the App Store accept?

Apple's page says you can upload one to 10 screenshots in .jpeg, .jpg and .png formats, and that images can't include alpha channels or transparencies. It lists sizes per display; the table shows the portrait sizes for the 6.9-inch and 6.5-inch displays.

Which of these can ChatGPT Image 2.5 make exactly?

None. Custom sizes must have both edges as multiples of 16, a longest edge of at most 3840, a ratio of at most 3:1, and 655,360 to 8,294,400 pixels. The shapes and pixel counts are fine; the multiple-of-16 rule is what fails. The last column is the smallest passing size within 1% of Apple's shape.

How do I get a file Apple accepts?

Generate at the nearest passing size, keep it as a PNG or JPEG, and scale it to Apple's size in your own editor. Scaling from a slightly different shape distorts the picture by the difference, which is under 1% here.

• Leave the app's real UI out of the prompt. Generate the background or the marketing frame, then place the true screen on top.
• Ask for no text and add captions yourself, so the words are exact.
• Export without transparency, since Apple's page says alpha channels are not allowed.

curl -X POST "https://api.sume.com/v1/images" \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-image-2.5",
    "prompt": "Vertical app store backdrop: soft teal gradient with abstract shapes, empty center for a phone screen, no text",
    "image_size": { "width": 560, "height": 1216 },
    "output_format": "png"
  }'

What if my app runs on more than one iPhone size?

Apple's page says the 6.5-inch sizes are required if the app runs on iPhone and screenshots for the 6.9-inch display are not provided, and that scaled 6.9-inch screenshots are used if accepted sizes are not provided. Check the current page before you decide which sizes to prepare, since Apple can change it.