Validate credit cards with the Luhn check in one API call

A mistyped card number costs you twice: the user sees a confusing decline, and your processor charges a fee for the failed authorization. You can catch most of those before they leave the browser. The Luhn algorithm is a checksum every real card number satisfies, so a number that fails it is guaranteed invalid and never needs to reach Stripe or Adyen.

This endpoint runs the Luhn check and detects the card brand in one POST. Here is the full call.

The request

curl -X POST https://api.botoi.com/v1/validate/credit-card \
  -H "Content-Type: application/json" \
  -d '{"number": "4111111111111111"}'

Send the number as a string. Spaces and dashes are stripped automatically, so 4111 1111 1111 1111 and 4111-1111-1111-1111 both work. The response tells you three things:

{
  "data": {
    "valid": true,
    "brand": "Visa",
    "type": "credit"
  }
}

• valid: passes the Luhn checksum or not.
• brand: Visa, Mastercard, Amex, Discover, JCB, Diners Club, or UnionPay.
• type: credit or debit, from the issuer identification number.

Validate at checkout in Node.js

Call the endpoint before you send anything to your processor. A failed Luhn check returns a clear error you can show the user, and you skip the authorization fee a fake number would have cost:

// Validate at checkout before you call your payment processor.
// Catches typos and fakes so they never cost you a declined-charge fee.
async function validateCard(number) {
  const res = await fetch("https://api.botoi.com/v1/validate/credit-card", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ number }),
  });
  const { data } = await res.json();
  return data; // { valid, brand, type }
}

const result = await validateCard("4111 1111 1111 1111"); // spaces are fine
if (!result.valid) {
  throw new Error("That card number is not valid. Check for a typo.");
}
console.log(`Detected ${result.brand} ${result.type} card`);

Block bad input in a React form

React Hook Form runs an async validator before submit, so an invalid number never fires the order. Wire the call straight into register:

// React Hook Form validator: block invalid cards before submit.
import { useForm } from "react-hook-form";

export function CheckoutForm() {
  const { register, handleSubmit, formState: { errors } } = useForm();

  const validateNumber = async (number) => {
    const res = await fetch("https://api.botoi.com/v1/validate/credit-card", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ number }),
    });
    const { data } = await res.json();
    return data.valid || "Enter a valid card number";
  };

  return (
    <form onSubmit={handleSubmit(submitOrder)}>
      <input
        {...register("number", { validate: validateNumber })}
        inputMode="numeric"
        placeholder="Card number"
      />
      {errors.number && <span class="error">{errors.number.message}</span>}
    </form>
  );
}

What it does and does not tell you

Luhn validation is a filter, not a guarantee. A passing number is well-formed; it does not prove the card exists or has funds. Only an authorization through your processor confirms that. Use this endpoint to reject obvious garbage cheaply and to drive the card-brand UI, then let your processor handle the real charge.

The credit card validator is one of roughly 200 single-purpose endpoints on botoi, alongside IBAN and VAT validation for the rest of your billing flow. All of them sit behind one API key with 5 req/min free. Try the call in the interactive playground or connect the MCP server to validate cards from Claude.