The Luhn algorithm—also known as the “Modulus 10 algorithm”—is a formula used to determine the accuracy of credit card numbers.

How does Luhn’s algorithm know when your fingers fumble? Every digit in a credit card number contributes a one-digit number to the final sum in the algorithm.

How does Luhn’s algorithm know when your fingers fumble? Every digit in a credit card number contributes a one-digit number to the final sum in the algorithm.