What is Luhn Check?
Check whether a credit card number is mathematically valid using the Luhn checksum, and identify its issuer from the number pattern. This is for format validation and testing only — it does not check whether a card actually exists or has funds. Use test numbers; nothing is sent anywhere.
How Luhn Check works
The Luhn algorithm doubles every second digit from the right, subtracts 9 from any result over 9, sums all digits, and passes if the total is divisible by 10.
The card type is detected from the leading digits (e.g. 4 = Visa, 34/37 = American Express).
Common uses
- Validate card-number format with Luhn
- Detect the card brand from the number
- Test payment forms with valid test numbers
- Catch typos in entered card numbers
Frequently asked questions
Does a valid result mean the card is real?
No. Luhn only checks the math. A real card also needs to exist, be active and have funds.
Is my card number stored?
No — the check runs entirely in your browser and nothing is saved or sent.
What card types are detected?
Visa, Mastercard, American Express, Discover, Diners Club, JCB and Maestro.