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Credit Card Validator

Credit Card Validator

Verify card numbers using the Luhn algorithm

Enter 13-19 digit card number (numbers only)
ⓘ Card number must be 13-19 digits
Use test card: 4111 1111 1111 1111

ⓘ About the Luhn Algorithm

This validator uses the Luhn algorithm (mod 10) to verify credit card numbers:

  • Step 1: Starting from the right, double every second digit
  • Step 2: If doubling results in a two-digit number, add the digits together
  • Step 3: Sum all the digits in the transformed number
  • Step 4: If the total modulo 10 equals 0, the card number is valid

This algorithm helps detect typos and invalid card numbers without contacting payment processors.