How does the Luhn Algorithm work?
The Luhn algorithm (also known as the "modulus 10" check) is a simple checksum formula used to validate credit card numbers, IMEI numbers, and other identification numbers. It detects any single-digit error and most transposition errors.
Supported Card Types
- Visa - Starts with 4, 16 digits
- Mastercard - Starts with 51-55 or 2221-2720, 16 digits
- American Express - Starts with 34 or 37, 15 digits
- Discover - Starts with 6011, 644-649, or 65, 16 digits
Privacy Notice
This tool runs 100% in your browser. Your card number is never transmitted to any server. We do not store, log, or collect any data you enter.
FAQ
Is this tool secure?Yes, all validation happens locally in your browser. Your card number never leaves your device.
Does this reveal card details?No, this tool only validates the format using the Luhn algorithm. It cannot determine card balance, validity, or owner information.