Aspect ratios

The aspect_ratio field is required on every generation request. The supported set depends on the model.

Special values

string

Infer the ratio from the first input image. Image-to-image only, and not supported by NanoBanana.

string

Let the model choose the ratio based on the prompt.

Passing a ratio that the model doesn’t support — for example auto or 4:1 to NanoBanana — results in a 422 validation error.