Nano Banana OSS Group

Nano Banana OSS (NB-OSS) beta group: image output is a URL instead of Base64, reducing transfer overhead and improving the experience. Best for scenarios where you use URLs directly.

Background (Read First)

What it is: This is a beta group whose image output is a URL rather than Base64, which reduces Base64 transfer overhead and improves the customer experience. Best for scenarios where you use the URL directly. If you have no special needs and can handle Base64-encoded image output, we still recommend using the “Normal Default Group” or the “NanoBanana Enterprise Group”.

Supported models (Nano Banana Pro and Gen 1):

• gemini-3-pro-image-preview
• gemini-3.1-flash-image-preview
• gemini-2.5-flash-image

Getting Started

1. Ask an admin to enable this visible group

   Contact an admin to enable the NB-OSS visible group for your account (add NB-OSS under “Edit User Info → Extra Visible Groups”).

   

   Edit User Info: add NB-OSS under Extra Visible Groups

2. Create a token: select the NB-OSS group

   When creating a token, set the billing model to “per-call billing” and select the NB-OSS group (Nano Banana PRO, image output as URL instead of Base64). You only swap the token; the request format stays the same.

   

   Create token: set billing model to per-call billing, select the NB-OSS group (1x) — image output as URL instead of Base64

3. Swap the token and test

   Swap in the token and run a test. Your code needs to handle parsing URL output — don’t simply replace Base64; supporting both works best.

Example Code

curl --location 'https://api.apiyi.com/v1beta/models/gemini-3-pro-image-preview:generateContent' \
  --header 'Authorization: Bearer sk-' \
  --header 'Content-Type: application/json' \
  --data '{
      "contents": [
          {
              "parts": [
                  {
                      "fileData": {
                          "fileUri": "https://raw.githubusercontent.com/apiyi-api/ai-api-code-samples/refs/heads/main/Vision-API-OpenAI/otter.png",
                          "mimeType": "image/png"
                      }
                  },
                  {
                      "text": "add five dogs"
                  }
              ],
              "role": "user"
          }
      ],
      "generationConfig": {"responseModalities": ["IMAGE"],
      "imageConfig": {
        "aspectRatio": "16:9",
        "imageSize": "2K"
      }},
      "safetySettings": []
  }'   > output.json

Output Example

The image URL is in the text field, and the thoughtSignature below it is the base64 of the reasoning process.

Response JSON: candidates → content → parts, the image URL is in the text field; thoughtSignature is the base64 of the reasoning

OSS Storage Region and Download Speed

Where Are the Images Stored?

The output image URLs are hosted on Alibaba Cloud OSS in Los Angeles (US West, us-west-1, North America region). The URLs look like:

https://<bucket-name>.oss-us-west-1.aliyuncs.com/xxxx.png

The subdomain part of the URL (the <bucket-name>, e.g. mycdn-gg) may change over time — do not hard-code the full domain in your code or firewall rules. If you need to match or allowlist the domain, match the suffix oss-us-west-1.aliyuncs.com (Alibaba Cloud’s official OSS domain), or more loosely allow *.aliyuncs.com.

Downloads Are Slow?

Since the storage node is in North America, direct downloads from some regions (e.g. mainland China) can be slow. Common causes and suggestions:

• Corporate network throttling / allowlist blocking of overseas traffic: ask your network admin to lift rate limits on and allowlist *.oss-us-west-1.aliyuncs.com (or *.aliyuncs.com).
• Re-host promptly: download the image as soon as you get the URL and re-upload it to your own storage / CDN before serving end users — don’t expose the OSS URL to end users long-term.
• Download via a server: if your local network is slow, download through an overseas server (or one with a good network route) first, then relay it.

For more network troubleshooting ideas (DNS, routing, cross-border bandwidth, etc.), see the FAQ: What to Do When CDN Image/Video Downloads Are Slow?

URL Won’t Open?

The key is to restore the escaped sequence \u0026 in the output JSON back to a normal &, while ignoring the base64 content after thoughtSignature.

The image link is in the text field; restore the JSON-escaped & back to the & in the URL, and ignore the base64 after thoughtSignature