Image Inputs

Analyze images with TheRouter.ai vision models

Send images through /chat/completions using image_url content parts. TheRouter.ai supports both URL-based images and base64 data URLs.

Image URL input

Use public URLs when possible for faster requests and smaller payloads.

TypeScript

const response = await fetch("https://api.therouter.ai/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: "Bearer <THEROUTER_API_KEY>",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "google/gemini-2.5-flash",
    messages: [
      {
        role: "user",
        content: [
          { type: "text", text: "What is shown in this image?" },
          {
            type: "image_url",
            image_url: {
              url: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/1280px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg",
            },
          },
        ],
      },
    ],
  }),
});

const result = await response.json();
console.log(result.choices[0].message.content);

Base64 image input

Use base64 data URLs for local files and private assets that are not publicly reachable.

Node.js

import fs from "node:fs/promises";

const image = await fs.readFile("./receipt.jpg");
const dataUrl = "data:image/jpeg;base64," + image.toString("base64");

const response = await fetch("https://api.therouter.ai/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: "Bearer <THEROUTER_API_KEY>",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "google/gemini-2.5-flash",
    messages: [
      {
        role: "user",
        content: [
          { type: "text", text: "Extract all totals from this receipt" },
          { type: "image_url", image_url: { url: dataUrl } },
        ],
      },
    ],
  }),
});

supported-content-types.txt

image/png
image/jpeg
image/webp
image/gif

Best practices

Put the text instruction first, then attach one or more images.
Use separate content entries for multiple images in the same message.
Check model capability metadata before sending image payloads.

Prompt ordering

If images must appear first, place your task instruction in a system message so the model gets clear guidance before processing the visuals.