Luhn check

A procedure for verifying credit card numbers.

What is a Luhn check?

The Luhn check or Luhn formula was developed by IBM scientist Hans Peter Luhn in the 1960s. It is widely used to validate credit card numbers, among other things. The check is in the public domain and may therefore be used by anyone. It is a quick way for companies to see whether a credit card is valid before clearing a transaction.

How the Luhn check works:

This formula checks a credit card number by using simple arithmetic to derive a number that must match the card’s check digit (last digit of the number).
Three steps are involved:

  • Starting with the second-to-last digit and moving left, double every other digit. If the result is 10 or more, add its digits together.
  • Add up all of the digits or sums, as the case may be.
  • If the last digit of the total matches the check digit or is zero, the credit card is valid.
Luhn Check

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