# Nano Banana 2.1 — Gemini generateContent

> Generate and edit Nano Banana 2.1 images with the official Gemini model ID, inline Base64 references, and image response parts.

Canonical URL: https://docs.uniall.ai/models/image/nano-series/nano-banana-2-1/gemini-format
Locale: en

## Overview

Use `gemini-nano-banana-2.1` to generate an image from text or edit up to 14 reference images with the Gemini request format. Each synchronous request returns one image as Base64 in an `inlineData` response part.

## Endpoint

```http
POST /v1beta/models/gemini-nano-banana-2.1:generateContent
```

The base URL is `https://api.uniall.ai`. The main examples use Google's official model ID `gemini-nano-banana-2.1`. The compatible URL `/v1beta/models/nano-banana-2.1:generateContent` also remains available.

## Authentication

Use your UniAI user API key:

```http
x-goog-api-key: <UNIAI_API_KEY>
Content-Type: application/json
```

## Request Parameters

Send one `user` entry in `contents`. Use camelCase field names.

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `contents` | array | Yes | Exactly one user-content entry. |
| `contents[].role` | string | Yes | `user`. |
| `contents[].parts[].text` | string | Yes | Non-empty generation or editing instruction. |
| `contents[].parts[].inlineData` | object | Conditional | Reference image for editing; add a part for each image, up to 14. |
| `contents[].parts[].inlineData.mimeType` | string | Conditional | `image/png`, `image/jpeg`, or `image/webp`. |
| `contents[].parts[].inlineData.data` | string | Conditional | Raw Base64 image bytes without a Data URL prefix. |
| `generationConfig.imageConfig.imageSize` | string | No | `1K`, `2K`, or `4K`; defaults to `1K`. |
| `generationConfig.imageConfig.aspectRatio` | string | No | One of the 14 ratios below. If omitted, the ratio follows the reference image or generated content. |
| `generationConfig.thinkingConfig.thinkingLevel` | string | No | `MINIMAL`, `MEDIUM`, or `HIGH`; defaults to `MEDIUM`. |
| `generationConfig.responseModalities` | string[] | No | Defaults to `["IMAGE"]`; also accepts `["TEXT", "IMAGE"]`. Text appears only if final text is actually generated. `["TEXT"]` alone is unsupported. |
| `generationConfig.candidateCount` | integer | No | Only `1` is accepted; each request returns one image. |

### Resolution And Reference Images

Supported aspect ratios:

```markdown
1:1  1:4  1:8  2:3  3:2  3:4  4:1
4:3  4:5  5:4  8:1  9:16  16:9  21:9
```

Resolution is a tier, not a fixed longest-edge pixel count. For example, a non-square `1K` result can be `1376 × 768`. `0.5K`, `512`, and `8K` are unsupported.

Editing requires 1 to 14 PNG, JPEG, or WebP reference images. Keep them in `parts` in the order described by your prompt. Order and duplicate entries are preserved; duplicates count toward the limit. Set `mimeType` to the actual image type and put only raw Base64 in `data`.

## Request Examples

### Text To Image

```bash
curl -X POST "https://api.uniall.ai/v1beta/models/gemini-nano-banana-2.1:generateContent" \
  -H "x-goog-api-key: <UNIAI_API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {"text": "Create a spring latte poster with a cream background and clear typography"}
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["IMAGE"],
      "imageConfig": {"imageSize": "2K", "aspectRatio": "16:9"},
      "thinkingConfig": {"thinkingLevel": "HIGH"},
      "candidateCount": 1
    }
  }'
```

### Image Editing

Replace `<BASE64_IMAGE_BYTES>` with the reference image's raw Base64 bytes before sending this request.

```bash
curl -X POST "https://api.uniall.ai/v1beta/models/gemini-nano-banana-2.1:generateContent" \
  -H "x-goog-api-key: <UNIAI_API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {"text": "Keep the cup shape and color; replace the background with a bright cafe"},
          {
            "inlineData": {
              "mimeType": "image/png",
              "data": "<BASE64_IMAGE_BYTES>"
            }
          }
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["IMAGE"],
      "imageConfig": {"imageSize": "2K", "aspectRatio": "4:5"},
      "thinkingConfig": {"thinkingLevel": "MEDIUM"},
      "candidateCount": 1
    }
  }'
```

Add another `inlineData` part for each additional reference image. To make a later edit, use the previous output image as a reference in a new independent request.

## Response Example

```json
{
  "candidates": [
    {
      "content": {
        "role": "model",
        "parts": [
          {
            "inlineData": {
              "mimeType": "image/png",
              "data": "<BASE64_IMAGE_BYTES>"
            }
          }
        ]
      },
      "finishReason": "STOP"
    }
  ]
}
```

| Response field | Description |
| --- | --- |
| `candidates[].content.parts[].inlineData` | Final image. Base64-decode `data` and save it according to the returned `mimeType`. |
| `candidates[].content.parts[].text` | Optional final text when requesting `["TEXT", "IMAGE"]` and final text is actually generated. Text is not guaranteed. |
| `usageMetadata` | May be present when actual usage metadata is available; do not require it to read the image. |

Find the part containing `inlineData` rather than assuming the first part is an image. The response is synchronous and has no task ID or polling step. A client timeout does not confirm that generation stopped; avoid automatically submitting the request again.

## Capability Limits And Common Errors

- Search is unavailable. Omit `tools`, `enable_web_search`, and `enable_image_search`; supplying them is rejected even when a search flag is `false`.
- Only a single user-content entry with text and image references is supported. Multi-turn history, thinking signatures or summaries, video/PDF input, Files, Interactions, and Batch APIs are unavailable in this image integration.
- `quality`, custom pixel `size` or `custom_size`, masks, transparent backgrounds, `seed`, and streaming output are unsupported.
- Do not use `/v1/chat/completions` or `/v1/images/tasks` for Nano Banana 2.1.
- An editing request without a reference image, more than 14 references, a Data URL prefix inside `inlineData.data`, an unsupported image size, text-only output, or a `candidateCount` other than `1` is invalid.
- Thinking control is available only for the new 2.1 integration. It is not enabled for `nano-banana-2`, `nano-banana-pro`, or fixed-resolution compatibility models.

## Related Pages

- [Nano Series](/models/image/nano-series)
- [Nano Banana 2.1 — OpenAI Images](./openai-format)
- [Gemini generateContent Format for other Nano models](/models/image/nano-series/gemini-format)