American Express Validator

American Express card numbers — 15 digits, 34/37 prefixes, Luhn check.

International Validation Generation

Try the demo NuGet: DocumentNumber.PaymentCardNumber.AmericanExpress.Validator

How validation works

The validator verifies the issuer prefix and length, then runs the Luhn algorithm over the digit string.

Install the package

bash

dotnet add package DocumentNumber.PaymentCardNumber.AmericanExpress.Validator

Validator in C#

Program.cs

using DocumentNumber.PaymentCardNumber.AmericanExpress.Validator;

var validator = new AmericanExpressPaymentCardValidator();
var isValid = validator.Validate("342633353118487");

Console.WriteLine(isValid ? "Valid" : "Invalid");

Live example

342633353118487 — a real American Express value accepted by the validator

Try American Express validation

Runs the exact same library code your application uses. Nothing you enter is stored.

Frequently asked questions

What is American Express?

American Express card numbers — 15 digits, 34/37 prefixes, Luhn check.

How does American Express validation work?

The validator verifies the issuer prefix and length, then runs the Luhn algorithm over the digit string.

How do I install the American Express validator package?

dotnet add package DocumentNumber.PaymentCardNumber.AmericanExpress.Validator

Is the value I enter in the demo stored?

No. Demo inputs are processed in memory for the current request only and are never persisted or shared.