ZenovayTools

Luhn Algorithm Checker

Validate credit card numbers, IMEI codes, and other identifiers using the Luhn (mod 10) algorithm. Identifies card type and checks digit validity.

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How to Use Luhn Algorithm Checker

  1. 1Enter a credit card number or IMEI code.
  2. 2See if the number passes the Luhn algorithm checksum.
  3. 3View the detected card type (Visa, Mastercard, Amex, etc.).
  4. 4Use for testing payment forms with valid test card numbers.
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Frequently Asked Questions

What is the Luhn algorithm?▾
The Luhn algorithm (also known as the mod 10 algorithm) is a simple checksum formula used to validate identification numbers. Created by IBM scientist Hans Peter Luhn in 1954, it works by: (1) From the rightmost digit, double every second digit. (2) If doubling produces a number > 9, subtract 9. (3) Sum all digits. (4) If the total is divisible by 10, the number is valid. It is designed to catch accidental single-digit errors and transpositions of adjacent digits.
Which numbers use the Luhn algorithm?▾
Credit and debit card numbers (all major networks: Visa, Mastercard, Amex, Discover, JCB, UnionPay), IMEI numbers (15-digit mobile device identifiers), Canadian Social Insurance Numbers (SIN), some national ID numbers, ICCID (SIM card identifiers), and NPI (National Provider Identifier) numbers in US healthcare. The algorithm is a basic sanity check — it does not guarantee a card is active or funds are available.
What are test credit card numbers?▾
Payment processors provide test card numbers for development. Stripe test cards: 4242 4242 4242 4242 (Visa), 5555 5555 5555 4444 (Mastercard), 3782 822463 10005 (Amex). PayPal sandbox uses the same Luhn-valid numbers. These numbers pass the Luhn check and are recognized as test cards by payment gateways — they cannot be used for real transactions. Never use real card numbers in development or testing.
What card types does this tool detect?▾
Card type is determined by the card number prefix (IIN/BIN): Visa (starts with 4, 13 or 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, 622126-622925, 644-649, or 65, 16 digits), JCB (starts with 3528-3589, 16 digits), Diners Club (starts with 300-305, 36, or 38, 14 digits).
Does a Luhn-valid number mean the card is real?▾
No. The Luhn algorithm only verifies the mathematical checksum of the number sequence. A number can pass Luhn validation but still be: non-existent (the bank has never issued that number), expired, cancelled, or declined. Actual card authorization requires a real-time check with the card network and issuing bank, including CVV/CVC verification, expiry date, billing address, and available balance. Luhn is purely a format check to catch typos.