Gemini Nano Banana 2.1

gemini-nano-banana-2.1 uses the Google official route, while gemini-nano-banana-2.1-ext uses a third-party route. Both use the same upstream model, but supported aspect ratios depend on the route and resolution; billing, image count and reference-size limits also differ.

The official route supports n from 1 to 4. Ext currently supports only n=1. Use separate Ext tasks or the official route when you need several images.

image_urls accepts publicly accessible HTTP(S) URLs or base64 data images. PNG, JPEG and WEBP are recommended. Official limits each reference to 20 MB; Ext allows 30 MB each and 50 MB combined. Upstream limits still apply even though the platform sets no reference-count cap.

Choose 1K, 2K or 4K and auto, 1:1, 2:3, 3:2, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9, 1:4, 4:1, 1:8 or 8:1. Both the official route and Ext support all these ratios at every resolution, including 1:4, 4:1, 1:8 and 8:1 at 2K and 4K. Defaults are 1K and auto. This model does not support 0.5K.

Official billing includes actual input tokens and output tokens, including image output and thinking. An image-output estimate is not the full task price. Ext is priced per image by resolution. Check the platform price list; the completed task's cost is the final charge.

This optional Ext setting is off by default. If the third-party route fails and the task completes through the official route, official token-based billing applies instead of Ext per-image pricing.

POST /v1/images/generations returns a task_id. Query GET /v1/tasks/{task_id} until the task completes or fails. Completed image links are returned in result.images[].url; include every URL when requesting multiple images.

Image links expire 72 hours after completion; use expires_at and save the files promptly. A task marked failed is fully refunded and reports cost=0. A network error while checking status does not by itself mean the task failed.