HIN OCR API

Automate marine vessel verification with our specialized HIN OCR API. We provide high-precision extraction for 15-character Hull Identification Numbers from low-contrast transom engravings, fiberglass embossments, and metal plates. The engine features built-in ISO 10087 strict format validation, prohibited character checks (I, O, Q), and a dynamic sliding-window algorithm to accurately resolve 20th and 21st-century model years.

Endpoint

POSThttps://api.structocr.com/v1/hin

Request Parameters

Important: This endpoint requires application/json Content-Type. Images must be sent as Base64 strings.

Parameter	In	Required	Description
x-api-key	Header	Required	Your unique API key generated from the dashboard.
Content-Type	Header	Required	Must be set to `application/json`.
img	Body (JSON)	Required	The Base64 encoded string of the hull image. Supports standard Data URI (e.g., `data:image/jpeg;base64,...`) Supports raw Base64 strings Max file size: 4.5MB Formats: JPG, PNG, WebP

Response Schema

The extracted and validated data is returned in the data object. The API automatically parses ISO 10087 structures and calculates full production years.

Field	Type	Description
hin_number	String \| null	The 15-character Hull Identification Number. Auto-formats with a hyphen (e.g., US-...).
is_valid	Boolean	True if the HIN passes ISO 10087 format rules and prohibited character checks.
validation_error	String \| null	Provides specific error details if validation fails (e.g., "Contains prohibited characters (I, O, Q)").
confidence	String	Recognition confidence ("High", "Medium", "Low", or "Medium (Validation Failed)").
parsed	Object \| null	Structured breakdown of the HIN. Will be populated if the base format is valid.
parsed.country_code	String	2-character country of origin code (e.g., 'US', 'CN').
parsed.manufacturer_code	String	3-character Manufacturer Identification Code (MIC).
parsed.serial_number	String	5-character hull serial number.
parsed.production_month	String	Full month name mapped from standard letter codes A-L (e.g., 'February').
parsed.production_year_short	String	Single digit representing the production year ending.
parsed.model_year	String	Full 4-digit model year resolved dynamically (e.g., '1999', '2024').

Code Examples

Request Implementation

curl -X POST https://api.structocr.com/v1/hin \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "img": "data:image/jpeg;base64,/9j/4AAQSkZJRg..."
  }'

Success Response (200 OK)

JSON EXAMPLE

{
  "success": true,
  "data": {
    "hin_number": "US-TNPD7474B899",
    "is_valid": true,
    "validation_error": null,
    "confidence": "High",
    "parsed": {
      "country_code": "US",
      "manufacturer_code": "TNP",
      "serial_number": "D7474",
      "production_month": "February",
      "production_year_short": "8",
      "model_year": "1999"
    }
  }
}

Error Responses

400 Bad Request - Invalid Input

Returned when JSON is invalid or image data is missing/corrupt.

{
  "status": 400,
  "code": "INVALID_REQUEST_FORMAT",  
  // or "INVALID_JSON", "INVALID_BASE64_FORMAT"
  "message":"The image data in 'img' field is malformed. Please check for illegal characters (spaces, newlines) or incorrect Base64 encoding."
}

402 Payment Required - Insufficient Credits

{
  "status": 402,
  "code": "INSUFFICIENT_CREDITS",
  "message": "Your account balance is insufficient to complete this operation."
}

413 Payload Too Large

The Base64 decoded image size exceeds 4.5MB.

{
  "error": "FILE_TOO_LARGE"
}

415 Unsupported Media Type

{
  "error": "INVALID_CONTENT_TYPE_USE_JSON"
}

422 Unprocessable Entity - Policy Violation

{
  "status": 422,
  "code": "CONTENT_POLICY_VIOLATION",
  "message": "The document content could not be processed due to safety policies."
}

500 Internal Server Error

{
  "status": 500,
  "code": "PROCESSING_ERROR",
  "message": "An internal error occurred while processing the document..."
}

503 Service Unavailable - System Busy

{
  "status": 503,
  "code": "SYSTEM_BUSY",
  "message": "HIN OCR is currently busy. Please try again."
}

Status Code Definitions

Code	Error Code	Description
200	SUCCESS	Recognition success
400	INVALID_REQUEST_FORMAT	Invalid payload or corrupted Base64. Ensure the image string has no whitespace, newlines, or illegal characters.
402	INSUFFICIENT_CREDITS	Account balance too low
413	FILE_TOO_LARGE	Decoded image exceeds 4.5MB
415	INVALID_CONTENT_TYPE	Not using application/json
422	CONTENT_POLICY_VIOLATION	AI safety/policy block
503	SYSTEM_BUSY	API Rate limit reached