Demand Gen 9:16 image ad size for YouTube Shorts

For a Shorts full-bleed image ad, Google recommends 1080x1920 (minimum 600x1067). Sume's custom pixels need both edges divisible by 16, so ask a GPT image model for 1088x1920 and trim 4 pixels from the left and right edges.

Google facts are from its Sep 24, 2026 Demand Gen Drop post and its image specification help page; Sume facts are from Image models, read 2026-09-30.

What does Google say about 9:16 image ads?

The Demand Gen Drop post says that on YouTube Shorts, "you and your customers will benefit from one-click experiences when you upload 9:16 full-bleed image ads". The help page adds that supported formats are .jpg or .png, that the square image max file size is 5 MB, and that safe zones for 9:16 images are similar to 9:16 videos. It lists the 9:16 row as "Recommended for YouTube Shorts".

Which 9:16 size passes Sume's check?

On GPT image models, image_size accepts custom pixels with both edges multiples of 16, a maximum edge of 3840, an aspect ratio of at most 3:1, and 655,360 to 8,294,400 total pixels. 1088x1920 passes every check (2,088,960 pixels, ratio about 1.76:1).

How do I get 1080 wide from Nano Banana?

Nano Banana models read the ratio, not the pixels, so send aspect_ratio: "9:16" and resize the result to 1080x1920 yourself.

Which file format and size limit apply?

Google's page lists .jpg and .png and a 5 MB limit for the square image row; check the 9:16 row's limits there. On Sume use output_format png or jpeg. The safe-zone guidance for 9:16 video is in Demand Gen video ad specs.