Fresh 2026

Images

How to send images via URL or base64 using the Gateway SDK, OpenAI SDK, or multiple-image requests.

Gateway supports two image input formats. Both work across all vision-capable providers - Gateway translates to the right format automatically.

Image URL

The simplest way to send an image. Pass a URL directly with the image_url content block.

response = client.responses.create(
    model="openai/gpt-5.1",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "Describe this image."},
                {"type": "image_url", "url": "https://example.com/photo.jpg"},
            ],
        }
    ],
)

const response = await client.responses.create({
  model: "openai/gpt-5.1",
  input: [
    {
      type: "message",
      role: "user",
      content: [
        { type: "text", text: "Describe this image." },
        { type: "image_url", url: "https://example.com/photo.jpg" },
      ],
    },
  ],
});

Image with source type

The image block gives you explicit control over the source type and media type. Use this for base64-encoded images or when you need to specify the format.

import base64

with open("photo.png", "rb") as f:
    image_data = base64.standard_b64encode(f.read()).decode("utf-8")

response = client.responses.create(
    model="anthropic/claude-sonnet-4-20250514",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "What do you see?"},
                {
                    "type": "image",
                    "source_type": "base64",
                    "media_type": "image/png",
                    "data": image_data,
                },
            ],
        }
    ],
)

response = client.responses.create(
    model="anthropic/claude-sonnet-4-20250514",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "What do you see?"},
                {
                    "type": "image",
                    "source_type": "url",
                    "media_type": "image/jpeg",
                    "data": "https://example.com/photo.jpg",
                },
            ],
        }
    ],
)

OpenAI SDK

If you're using the OpenAI SDK pointed at Gateway, use the standard OpenAI image format.

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api-gateway.merge.dev/v1/openai",
)

response = client.chat.completions.create(
    model="gpt-5.1",
    messages=[
        {
            "role": "user",
            "content": [
                {"type": "text", "text": "What's in this image?"},
                {"type": "image_url", "image_url": {"url": "https://example.com/photo.jpg"}},
            ],
        }
    ],
)

Multiple images

Pass multiple image blocks in the same message to compare or analyze several images at once.

response = client.responses.create(
    model="openai/gpt-5.1",
    input=[
        {
            "type": "message",
            "role": "user",
            "content": [
                {"type": "text", "text": "Compare these two images."},
                {"type": "image_url", "url": "https://example.com/before.jpg"},
                {"type": "image_url", "url": "https://example.com/after.jpg"},
            ],
        }
    ],
)

Each image is estimated at ~765 tokens for context window and compression calculations. Keep this in mind when sending multiple images in a single request.