Credit Card Validator
Frequently Asked Questions
Everything you need to know about card validation
What is the Luhn algorithm?
The Luhn algorithm (or mod 10 formula) is a simple checksum used to validate identification numbers such as credit cards, IMEI codes and others. It doubles every second digit starting from the right, sums all the digits and checks that the total is a multiple of 10. It catches typing errors, it does not guarantee the card is real.
How is the card network detected?
The network is detected from the first digits of the number (the IIN/BIN). For example Visa cards start with 4, American Express with 34 or 37, Mastercard with 51-55 or 22-27, Discover with 6011 or 65. Each network also has specific valid lengths (Amex has 15 digits, most others 16).
Does a valid number mean the card is usable?
No. A tool like this only checks that the number respects the Luhn algorithm and the network's format rules. It cannot know whether the card really exists, is active, expired or has available funds: that verification only happens bank-side during a real transaction. Also, everything is computed in your browser, sending nothing.
Which card networks does the validator recognise?
It recognises Visa, Mastercard, American Express, Discover, Diners Club, JCB, UnionPay and Maestro, reading the first digits of the number (IIN/BIN) and checking the length is one of the valid ones for that network.
Does a valid number mean the card works?
No. The check only says the number follows the Luhn algorithm and the format of its network. Whether the card exists, is active, has expired or has funds is something only the bank finds out during a real transaction.