Credit Card Number Validator
Type a card number to instantly check whether it passes the Luhn checksum and see which payment network it matches — a quick way to test checkout form validation logic.
How to use
As you type, the tool strips spaces and dashes, runs the Luhn (mod 10) algorithm used by essentially every major card network to catch typos, and matches the number's prefix against known card brand ranges (Visa, Mastercard, Amex, Discover, and others).
This checks mathematical validity and format only — it cannot and does not check whether a card actually exists, is active, or has any funds available. It's meant for developers and QA testers verifying that a checkout form correctly accepts valid-format numbers and rejects invalid ones, using well-known published test numbers rather than real card data.
FAQ
What does the Luhn algorithm actually check?
It's a checksum formula (doubling every second digit from the right, summing the digits, checking the total is divisible by 10) built into how card numbers are issued, so it catches most single-digit typos and transposed digits. It says nothing about whether the account behind the number is real or active.
Can this tool be used to generate working card numbers?
No — it only validates numbers you provide; it doesn't generate new ones. Luhn-valid numbers that aren't real, active accounts are useless for any actual transaction — payment processors verify against the issuing bank, which this checksum has no bearing on.
Why does my real card number show as invalid?
Check for a typo, extra digit, or missing digit first — Luhn catches those reliably. If the number is definitely correct as printed, the checksum should pass; a failure on a genuinely correct number would be unusual.
How is the card brand detected?
By matching the number's leading digits against publicly documented ranges each network uses (Visa starts with 4, Mastercard with 51–55 or 2221–2720, Amex with 34 or 37, and so on). This is a format check, not a lookup of any real account data.