API Fundamentals

The Fit-it-on Developer API provides programmatic access to our AI generation models. It follows standard REST architectural styles, uses predictable resource-oriented URLs, and accepts JSON-encoded request bodies.

Asynchronous Execution

All image generations are processed asynchronously. High-resolution AI renders (2k or 2048x2048 samples) take time, and a synchronous connection would inevitably time out.

1. Submit a Job: You send a POST /v1/run request with your input data.
2. Receive ID: The API immediately returns a 200 OK with a prediction_id.
3. Poll for Status: You periodically call GET /v1/status/{predictionId}.
4. Completion: When the status transitions to succeeded, the URLs to your generated images will be available in the output array.

Base URL

All requests must be made over HTTPS to our production environment:

https://fititon.app/api

Content Types

All POST and PATCH requests must include the following header to specify the payload format:

Content-Type: application/json

The API also returns all responses strictly in JSON format.

Webhooks

If you provide a webhook_url at the root of your JSON payload, we will send an HTTP POST request to that URL as soon as the asynchronous job completes (either successfully or with an error).

Webhook Payload Example:

{
  "id": "123e4567-e89b-12d3-a456-426614174000",
  "status": "success",
  "output": [
    "https://storage.fititon.com/results/result-123.jpg",
    "https://storage.fititon.com/results/result-124.jpg"
  ],
  "error": null,
  "created_at": "2026-07-03T10:00:00.000Z",
  "updated_at": "2026-07-03T10:00:15.000Z"
}

Request Limits & Handling

To prevent abuse, the API enforces a rate limit based on your active Developer Plan tier.

If you exceed your limit, you will receive a 429 Too Many Requests error. Your application should gracefully handle this by implementing exponential backoff.