American Express Card Number Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching american express card number, ported and verified for JavaScript. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// American Express Card Number
// ReDoS-safe | RegexVault — Finance > Card Numbers

const americanExpressCardNumberRegex = /^3[47][0-9]{13}$/;

function validateAmericanExpressCardNumber(input: string): boolean {
  return americanExpressCardNumberRegex.test(input);
}

// Example
console.log(validateAmericanExpressCardNumber("378282246310005")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Card Numbers category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Amex uses 15-digit card numbers (unlike 16-digit Visa/Mastercard). CVV is 4 digits on the front (not 3 on the back). Amex uses different group format for display: 4-6-5.