Mac App Store screenshot size: which of the 4 Sume can make

Apple accepts one of four Mac screenshot sizes, all 16:10: 1280 x 800, 1440 x 900, 2560 x 1600 or 2880 x 1800. Sume's image API can output 1280 x 800 and 2560 x 1600 through custom image_size. 1440 x 900 fits only the Timeline route, and 2880 x 1800 fits neither.

Sizes are from Apple's screenshot specifications, read 2026-10-01; the Sume rules are from https://docs.sume.com/models/images and https://docs.sume.com/models/timeline.

How do the four Mac sizes compare to Sume's limits?

The image rule needs multiples of 16, a max edge of 3840, aspect at most 3:1 and 655,360-8,294,400 pixels.

Is 16:10 in the aspect ratio list?

No. The image API's normalized ratio list is 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 and 21:9, with no 8:5 or 16:10. To get 16:10 you use custom pixels, which is why the two multiple-of-16 sizes work and the other two do not. The aspect ratio post has the full rules.

How do I get 1440 x 900?

Use the Timeline route: a still as video[].source_url (stills are static holds), output.width 1440 and output.height 900, then a png frame from video_frames. Both edges are even and inside 256-2160. Set fit yourself, because the default cover crops a source that is not 16:10.

What do I do for 2880 x 1800?

Generate 2560 x 1600, which has the same 16:10 shape, then scale it to 2880 x 1800 in your own tooling. Sume's exact pixel size post explains why its upscale is not a guarantee of an arbitrary target size. Apple says to pick one of the four, so a 1280 x 800 or 2560 x 1600 set avoids the problem.