Luhn Validator

Check if a card number is mathematically valid using the Luhn Algorithm.

How the Luhn Algorithm Works

The Luhn algorithm, also known as the "modulus 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and IMEI numbers. It was designed to protect against accidental errors, such as typing a wrong digit.

**Note:** This tool only checks the mathematical validity of the number string. It does not check if a card is active, has funds, or is a real bank-issued card. All processing happens locally in your browser; we never store or transmit your input.