Check whether a credit or debit card number passes the Luhn checksum algorithm and identify its card network.
The Luhn algorithm is a simple checksum formula used to validate a wide range of identification numbers, most commonly credit and debit card numbers. This Credit Card Number Validator checks whether a given number passes the Luhn checksum and identifies which major card network's numbering pattern it structurally matches, entirely inside your browser with no card data ever transmitted anywhere.
It's important to understand precisely what this kind of check does and doesn't tell you. The Luhn algorithm exists purely to catch simple data-entry errors, not to verify that a card is real, currently active, or has any funds available. Every legitimately issued card number passes this checksum, but plenty of made-up numbers that happen to satisfy the same formula will also pass, without corresponding to any real account whatsoever.
Starting from the rightmost digit and moving left, every second digit is doubled; if that produces a result greater than 9, the two digits are added together. All digits are then summed. If the total is evenly divisible by 10, the number passes the Luhn check. This formula was developed by IBM scientist Hans Peter Luhn and patented in 1954, and it remains in near-universal use today.
Major card networks follow publicly documented numbering conventions for their leading digits. Visa cards start with 4. Mastercard numbers start with 51 through 55, or specific ranges beginning with 222100 through 272099. American Express cards start with 34 or 37 and use a shorter 15-digit format. Discover cards typically start with 6011 or 65.
Developers building payment forms commonly use Luhn validation as an immediate, client-side sanity check before submitting a card number for actual payment processing, catching obvious typos before they reach a payment gateway.
This tool cannot check whether a card number corresponds to a real, active account with any available balance, that information is held exclusively by banks and card networks. Never enter another person's actual card details into any website you don't fully trust.
Real payment processing involves several additional layers beyond the Luhn checksum, including the card verification value (CVV) printed on the physical card, address verification systems, and ultimately live authorization from the issuing bank itself. None of these additional layers can be checked or simulated by a client-side tool, since they require direct, authorized communication with financial networks that are tightly access-controlled for good security reasons.
If you're implementing Luhn validation in your own project, remember to always pair it with genuine server-side validation through your actual payment processor, never treat a client-side Luhn pass as sufficient authorization on its own. Client-side checks exist purely to improve user experience by catching typos early, not to serve as any form of real security or fraud boundary.
Keep in mind that card numbering conventions occasionally shift as networks introduce new ranges, so network detection here should be treated as a helpful approximation based on current, publicly known patterns rather than an exhaustive, permanently guaranteed classification.
No, it only confirms the number is structurally well-formed. Many made-up numbers that were never issued will also pass this check.
No, the entire Luhn calculation happens locally in your browser using JavaScript.
It compares the number's leading digits against publicly documented Issuer Identification Number ranges used by major networks.
As an immediate client-side sanity check to catch obvious typos in a payment form before submitting for actual processing.
No, that information is held exclusively and securely by banks and card networks.
Idiot Security Tools