How to Use Nano Banana 2 API: Complete Tutorial with Code Examples (2026)

TL;DR

• Nano Banana 2 (gemini-3.1-flash-image-preview) launched Feb 26, 2026 — Pro-level quality at Flash speed
• Requires a paid API key. Free tier quota for image generation is zero
• Google pricing: $0.101/image (2K), $0.150/image (4K). EvoLink offers ~20% lower at $0.0806 (2K)
• Three ways to access: Google AI Studio (no code), Gemini API (Python/Node.js), or via a unified gateway
• This tutorial gets you generating images in under 10 minutes

What Is Nano Banana 2?

Nano Banana 2 is Google's latest image generation model, built on Gemini 3.1 Flash Image. On Feb 26, 2026, Nano Banana 2 replaced Nano Banana Pro as the default image model across Gemini app's Fast, Thinking, and Pro modes.

• Model ID: gemini-3.1-flash-image-preview
• Resolution: 512px to 4K, native aspect ratios including 4:1, 1:4, 8:1, 1:8
• Subject consistency: Up to 5 characters + 14 objects per generation
• Text rendering: Improved multi-language in-image text
• Thinking levels: Minimal (default) vs. High/Dynamic for complex prompts
• AI identification: SynthID + C2PA Content Credentials

Prerequisites: What You Need Before Starting

This is where most developers get stuck. On Reddit, the #1 complaint is hitting quota errors without understanding why.

If you try with a free key, you'll get:

Option A: Google Cloud Billing

1. Go to Google AI Studio
2. Click Get API Key → Create API key
3. Link a billing account in Google Cloud Console → Billing
4. Enable the Gemini API in your project
5. Your key now works for image generation

Option B: Third-Party Gateway

Method 1: Google AI Studio (No Code)

The fastest way to test without writing code:

1. Open AI Studio
2. Select gemini-3.1-flash-image-preview from the model dropdown
3. Type a prompt: "A photorealistic golden retriever puppy in a sunlit meadow"
4. Click Run

If you see "only available for paid tier users," your billing isn't linked yet (see Prerequisites above).

Great for prompt testing before you write any integration code.

Method 2: Gemini API Direct

Python

pip install google-generativeai

import google.generativeai as genai
import base64

genai.configure(api_key="YOUR_PAID_API_KEY")

model = genai.GenerativeModel("gemini-3.1-flash-image-preview")

response = model.generate_content(
    "A photorealistic golden retriever puppy sitting in a sunlit meadow, "
    "soft bokeh background, warm afternoon light",
    generation_config=genai.GenerationConfig(
        response_modalities=["image", "text"],  # Optional; model defaults to both text and image
    ),
)

for part in response.parts:
    if part.inline_data:
        image_data = base64.b64decode(part.inline_data.data)
        with open("output.png", "wb") as f:
            f.write(image_data)
        print("Image saved to output.png")
    elif part.text:
        print(f"Response: {part.text}")

Node.js

npm install @google/generative-ai

const { GoogleGenerativeAI } = require("@google/generative-ai");
const fs = require("fs");

const genAI = new GoogleGenerativeAI("YOUR_PAID_API_KEY");

async function generateImage() {
  const model = genAI.getGenerativeModel({
    model: "gemini-3.1-flash-image-preview",
  });

  const result = await model.generateContent({
    contents: [
      {
        role: "user",
        parts: [
          {
            text: "A photorealistic golden retriever puppy sitting in a sunlit meadow, soft bokeh background, warm afternoon light",
          },
        ],
      },
    ],
    generationConfig: {
      responseModalities: ["image", "text"],
    },
  });

  const response = result.response;
  for (const part of response.candidates[0].content.parts) {
    if (part.inlineData) {
      const buffer = Buffer.from(part.inlineData.data, "base64");
      fs.writeFileSync("output.png", buffer);
      console.log("Image saved to output.png");
    } else if (part.text) {
      console.log("Response:", part.text);
    }
  }
}

generateImage();

Method 3: OpenAI-Compatible Gateway (EvoLink)

If you already use the OpenAI SDK, you can generate images without changing your code structure — just point to a different base URL.

Python (OpenAI SDK)

pip install openai

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_EVOLINK_API_KEY",
    base_url="https://api.evolink.ai/v1",
)

response = client.chat.completions.create(
    model="gemini-3.1-flash-image-preview",
    messages=[
        {
            "role": "user",
            "content": "A photorealistic golden retriever puppy sitting in a sunlit meadow",
        }
    ],
)

print(response.choices[0].message.content)

Node.js (OpenAI SDK)

npm install openai

const OpenAI = require("openai");

const client = new OpenAI({
  apiKey: "YOUR_EVOLINK_API_KEY",
  baseURL: "https://api.evolink.ai/v1",
});

async function generateImage() {
  const response = await client.chat.completions.create({
    model: "gemini-3.1-flash-image-preview",
    messages: [
      {
        role: "user",
        content:
          "A photorealistic golden retriever puppy sitting in a sunlit meadow",
      },
    ],
  });

  console.log(response.choices[0].message.content);
}

generateImage();

Why use a gateway? One API key for multiple models (NB2, Pro, GPT-4o Image, Seedream). No Google Cloud billing setup. Same model, same output.

Pricing Breakdown

Text token costs are negligible (~$0.0001 per prompt). The image output token is where the cost is.

For batch workloads (100+ images/day), the savings compound quickly.

Prompt Engineering Tips

Be Specific

Use Style Keywords

Leverage Thinking Levels

For complex prompts with multiple subjects, enable higher thinking:

generation_config=genai.GenerationConfig(
    response_modalities=["image", "text"],
    thinking_config={"thinking_budget": 1024},  # Higher = more reasoning
)

Multi-Turn Editing

Generate an image, then refine it in follow-up messages:

Troubleshooting

Quota Exceeded Error

400 Bad Request

Common causes:

• Typo in model ID
• Unsupported aspect ratio

Text Response Instead of Image

generation_config=genai.GenerationConfig(
    response_modalities=["image", "text"],
)

FAQ

A: No. Image generation requires a paid API key with billing enabled. Free tier quota is 0.

A: 2K: $0.101 Google direct. 4K: $0.150. Plus negligible text token costs (~$0.0001/prompt). Pricing as of Feb 2026.

A: Google's RPM limits vary by billing tier and aren't fully documented. Implement exponential backoff for 429 errors.

A: Yes. Multi-turn conversations — generate an image, then describe edits in follow-up messages.

A: 512px, 1K, 2K, 4K. Aspect ratios: 1:1, 16:9, 9:16, 4:3, 3:4, 4:1, 1:4, 8:1, 1:8.

A: SynthID (invisible) + C2PA Content Credentials. Not visually visible but detectable by verification tools.

Start Generating

Three steps:

1. Get a paid API key (Google AI Studio or evolink.ai/signup)
2. Copy the code above
3. Run it