Credit Card Validator

The Luhn Algorithm

Credit card numbers are validated using the Luhn algorithm (also known as "mod 10"), a simple checksum formula used to validate identification numbers including credit card numbers.

How it works:

1. Starting from the rightmost digit, double every second digit
2. If doubling results in a number > 9, subtract 9
3. Sum all the digits
4. If the total is divisible by 10, the number is valid

Card Network Identification

Card networks can be identified by their IIN (Issuer Identification Number) prefix:

Limitations

This validator only checks:

• Number format and length
• Luhn algorithm checksum
• Card network identification

It does NOT verify:

• Whether the card actually exists
• Account status or balance
• Expiration date or CVV