Credit Card Number Validator
Disclaimer
This tool only checks number formatting using the public Luhn checksum — it cannot tell you whether a card is active, real, or belongs to any person or account.
Check the issuing bank with the BIN checker
Explore CardsWhat the Luhn Algorithm Actually Checks
Every major card network — Visa, Mastercard, RuPay, American Express, Discover, Diners Club — appends a final check digit to its card numbers, computed using a public formula called the Luhn algorithm. The algorithm doubles every second digit from the right, sums all the digits together, and checks whether the total is a multiple of 10. It's a checksum, in the same family as the check digits used on ISBNs and IMEI numbers — designed to catch a single mistyped or transposed digit, nothing more.
Why Luhn Validation Isn't a Fraud Check
A number passing the Luhn check tells you only that it is mathematically well-formed — not that it belongs to a real account, has any funds behind it, or is currently active. Fraudsters can and do generate Luhn-valid numbers trivially; real fraud prevention happens at the payment processor and issuing bank level, checking the number against actual issued accounts, CVV, billing address, and behavioral signals — none of which a client-side checksum can see. Treat this tool strictly as a data-entry sanity check, not a security control.
How Card Networks Are Identified From the Number
Beyond the checksum, the leading digits of a card number (the BIN/IIN, typically the first 6–8 digits) identify which network issued it. Numbers starting with 4 are Visa; 51–55 or certain 2221–2720 ranges are Mastercard; 34 or 37 are American Express; 60, 6521/6522, 81, 82, or 508 prefixes typically indicate RuPay. This validator detects the likely network from those same prefix ranges — for a deeper lookup including the specific issuing bank, use our BIN Checker.
Common Reasons a Real Card Might "Fail" This Check
If you paste in a real card number and it fails, the most common causes are a typo, an extra or missing digit, or accidentally including non-numeric characters that got mis-stripped. Genuine, currently-issued cards from every major network are Luhn-valid by construction — a real card failing this check almost always points to a data-entry error rather than anything wrong with the card itself.
Where Luhn Validation Is Used in the Real World
Payment gateways, POS terminals, and e-commerce checkout forms all run a Luhn check as the very first, cheapest validation step before ever contacting a bank — it catches a meaningful share of typos instantly, without a network round trip. This is also why developer teams commonly need Luhn-valid test numbers to exercise those same validation paths during development; our Test Card Number Generator produces exactly that.