Credit Card Validator
Check whether a card number passes the Luhn checksum and identify its brand — Visa, Mastercard, Amex, or Discover.
Private by design: everything runs in your browser — nothing you type is stored, logged, or transmitted anywhere. Note this tool only checks the checksum math and the brand pattern; it cannot tell you whether a card is real, active, or has funds.
How it works
Every major card number embeds a built-in typo detector called the Luhn checksum. Starting from the rightmost digit and moving left, every second digit is doubled; if a doubled value exceeds 9, its digits are summed (equivalently, subtract 9). Add everything up: if the total is a multiple of 10, the number is structurally valid. This catches virtually all single-digit typos and most transpositions — which is why payment forms validate instantly before contacting the bank. The brand comes from the leading digits (the Issuer Identification Number): numbers starting with 4 are Visa, 51–55 and 2221–2720 are Mastercard, 34/37 are American Express, and 6011, 622, 64, or 65 are Discover. Passing the checksum only proves the number could exist; real authorization always happens with the card network.