Compute check digit API

Computes the check digit for a payload under a chosen scheme: Luhn, GS1 mod-10, ISO 7064 mod-11, ISO 7064 MOD 97-10, Verhoeff, or Damm. Answers 'What check digit completes this number?', 'How do I generate a valid identifier under scheme X?'.

Price$0.04per request

MethodPOST

Route/v1/validate/check-digit

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

check-digitluhnmod-10mod-11mod-97verhoeffdammcomputeiso-7064

API URLhttps://x402.hexl.dev/v1/validate/check-digit

Integration docs

Example request

{
  "scheme": "luhn",
  "payload": "7992739871"
}

Example response

{
  "scheme": "luhn",
  "payload": "7992739871",
  "checkDigit": "3",
  "full": "79927398713",
  "reason": "Luhn (mod-10 double-every-other) check digit = 3."
}

Input schema

{
  "type": "object",
  "required": [
    "scheme",
    "payload"
  ],
  "properties": {
    "scheme": {
      "type": "string",
      "description": "luhn | gtin | mod-11 | mod-97 | verhoeff | damm.",
      "examples": [
        "luhn",
        "mod-97",
        "verhoeff"
      ]
    },
    "payload": {
      "type": "string",
      "description": "The body to compute a check digit for.",
      "examples": [
        "7992739871"
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}