Credit Card Validator

What the card validator checks

This tool checks whether a card number is structurally valid: that it has a recognised prefix, the right length for its network, and a correct check digit according to the Luhn algorithm. It is useful for catching typos before a payment form rejects the number.

It does not check whether a card is active, has funds, or belongs to you. A number can pass the Luhn check and still be declined.

How the Luhn algorithm works

The Luhn algorithm (also called the mod 10 algorithm) is a simple checksum used by almost every payment card:

1. Starting from the rightmost digit and moving left, double every second digit.
2. If doubling gives a number greater than 9, subtract 9 from it.
3. Add up all the digits, doubled and untouched.
4. If the total is a multiple of 10, the number passes the check.

Example: for the number 79927398713, doubling every second digit from the right and adding everything gives 70, which is divisible by 10, so the number is valid. Changing any single digit breaks the total, which is why the check catches most typing mistakes.

Card number lengths and prefixes

Common reasons a valid number is still declined

• The expiry date or CVV is wrong.
• The card has no available balance or has been blocked by the issuer.
• The merchant does not accept cards from that country or prepaid cards.
• The billing address or 3-D Secure check failed.

To see which bank and country a card belongs to, use the BIN checker. Merchants weighing up disputes can use the chargeback vs refund calculator.