Credit Card Number Validator

Credit card number validation is a process used to check if a credit card number is likely to be authentic based on its format and a checksum algorithm, most commonly the Luhn algorithm. This tool performs such a check.

What is the Luhn Algorithm?

The Luhn algorithm, also known as the "modulus 10" or "mod 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, and National Provider Identifier numbers. It was developed by IBM scientist Hans Peter Luhn and patented in 1960.

The algorithm works by:

• Dropping the last digit (the check digit).
• Reversing the remaining digits.
• Multiplying the digits in odd positions (1st, 3rd, 5th, etc. from the right, post-reversal) by 2.
• If any product of this doubling is greater than 9, subtract 9 from it (or sum its digits).
• Summing all the resulting digits (including those not doubled).
• The check digit is the number that, when added to this sum, results in a number divisible by 10.

Our implementation directly calculates the sum including the check digit and verifies if the total sum is divisible by 10.

Why Use a Validation Tool?

• Reduce Typos: Helps catch mistyped card numbers at the point of entry, improving data quality before it's sent for processing.
• Preliminary Check: Acts as a first line of defense against obviously incorrect card numbers. It doesn't verify if the card is active, has funds, or is legitimate in terms of belonging to someone – only that the number sequence itself is plausible.
• Developer Testing: Useful for developers when building and testing payment forms or systems that handle credit card data.
• User Experience: Providing immediate feedback to users about potential errors in the card number they've entered can improve the overall user experience on e-commerce sites or payment forms.