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Card Number Validator

Luhn check and card brand detection

This is arithmetic only, with no bank lookup: passing Luhn means the number is not a typo, not that the card exists or works. Never type a real card number into any tool — the samples below are the brands' published test numbers.

Card number

Public test numbers

The Luhn algorithm (ISO/IEC 7812) walks right to left, doubling every second digit and subtracting 9 when the product exceeds 9, then sums everything — divisible by 10 means it passes. It is designed to catch the two commonest typing mistakes, a single wrong digit and a transposed pair, not to prove authenticity: anyone can construct a number that passes.

All processing happens locally in your browser. Your data is never uploaded to a server.