Credit Card Validator
Validate credit card numbers using the Luhn algorithm. Auto-detects card type and shows step-by-step validation.
How to Use the Credit Card Validator
- Enter a card number -- Type or paste a credit card number. Spaces are added automatically for readability.
- Click Validate -- The tool runs the Luhn algorithm and detects the card network.
- View results -- See whether the number is valid, the detected card type, and the digit count.
- Review the breakdown -- Expand the Luhn Algorithm Breakdown to see each step of the calculation.
About the Luhn Algorithm
The Luhn algorithm, also known as the "modulus 10" or "mod 10" algorithm, was created by IBM scientist Hans Peter Luhn in 1954. It is a simple checksum formula used to validate a variety of identification numbers, most notably credit card numbers, IMEI numbers, and Canadian Social Insurance Numbers.
The algorithm works by doubling every second digit from right to left, subtracting 9 from any result over 9, then summing all digits. If the total modulo 10 equals zero, the number is valid. This catches all single-digit errors and most transpositions of adjacent digits, making it an effective first-line check against accidental errors in number entry.
Frequently Asked Questions
The Luhn algorithm is a checksum formula that validates identification numbers like credit card numbers. It doubles every second digit from the right, sums all digits (subtracting 9 from doubled values over 9), and checks if the total is divisible by 10.
No. This tool only validates the mathematical format of the card number. It cannot determine if the card exists, is active, or has available funds. It is purely a format and checksum validation tool.
Card types are identified by their IIN/BIN (Issuer Identification Number / Bank Identification Number) prefix. Visa cards start with 4, Mastercard with 51-55 or 2221-2720, American Express with 34 or 37, and Discover with 6011, 644-649, or 65.