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Image Inputs

Models that take image input can read images you attach to POST /v1/chat/completions and POST /v1/messages requests, in each API's standard shape. The Router passes the image to the provider unchanged and sends the request only to providers of the model that take images.

Which models take images​

A model takes images when architecture.input_modalities in /v1/models contains "image":

curl -s https://router-api.0g.ai/v1/models \
  | jq -r '.data[] | select(.architecture.input_modalities | index("image"))
                   | select(.architecture.output_modalities == ["text"]) | .id'

The catalog lists a model as taking images when any of its providers does, on any API. A model can take images on one API only: glm-5.3-flash, for example, takes them on /v1/chat/completions but not on /v1/messages. GET /v1/providers?model=<id> shows each provider's supported_formats and architecture.input_modalities.

Request​

Send the image as base64. Use a data: URI on /v1/chat/completions, and an Anthropic base64 source on /v1/messages.

curl https://router-api.0g.ai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-YOUR_API_KEY" \
  -d '{
    "model": "qwen3.8-flash",
    "messages": [{
      "role": "user",
      "content": [
        {"type": "text", "text": "What color is this image? Answer in one word."},
        {"type": "image_url", "image_url": {
          "url": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAIAAAD8GO2jAAAAKklEQVR42mO4oKBAU8QwasGoBaMWjFowasGoBaMWjFowasGoBaMWDBULAE7YQD2B7wk2AAAAAElFTkSuQmCC"
        }}
      ]
    }]
  }'

The response is the model's normal answer. A request can carry several images, in any message.

You can also pass a link instead of the data: an https:// URL in image_url.url, or a {"type": "url", "url": "..."} source on /v1/messages. The provider then downloads the image itself, and the request fails with the provider's error when:

  • the provider does not accept image links, or
  • the provider cannot download the URL in time (for example, a host it cannot reach).

Because a model is often served by several providers, a link can work on one request and fail on the next. Send base64 when you need the request to succeed reliably.

Errors​

StatusCause
400 model_not_capableNo provider of the model takes images on this API. The message says model <id> does not accept image input. Not charged
413The request body, images included, is over 20 MB after base64 encoding
Provider's error, usually 400The provider refused the image, for example a link it could not download (Download multimodal file timed out), or an image larger than it accepts

Billing​

There is no fee for images. The provider counts each image as input tokens, billed at the model's normal input price. Some providers report the image share separately in usage.prompt_tokens_details.image_tokens:

"usage": {
  "prompt_tokens": 138,
  "prompt_tokens_details": {"cached_tokens": 0, "image_tokens": 66, "text_tokens": 72},
  "completion_tokens": 46,
  "total_tokens": 184
}
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