Test cards:
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Enter a card number
Test cards above or paste any number to check Luhn validity
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How the Luhn algorithm works
- Reverse the card digits (e.g.,
4111111111111111→1111111111111114) - Double every second digit. If the doubled value is > 9, sum its digits (e.g., 16 → 1+6=7)
- Sum all digits. If the total is divisible by 10, the number passes the Luhn check
- Luhn validates format only — it does not check if the card is real, active or has funds
Card brand prefixes
- Visa: starts with 4 (13, 16, 19 digits)
- MasterCard: 51-55 or 2221-2720 (16 digits)
- American Express: 34 or 37 (15 digits)
- Discover: 6011, 65, 644-649 (16 digits)
- JCB: 3528-3589 (16-19 digits)
- UnionPay (银联): 62 (16-19 digits)
- Diners Club: 300-305, 36, 38 (14-19 digits)