How to Check a Number with the Luhn Validator
Paste a card number or another number that uses the Luhn check, see if it is valid, and learn what the result means.
2 min read
To check a number, open the Luhn validator and paste the number. The tool shows right away if the number is valid or invalid. Paste only digits, with no spaces or dashes.
Valid means the digits pass the Luhn check. Invalid means a digit is wrong, missing, or swapped. It can also mean that the number does not use the Luhn check at all.
What a valid result means
A valid result does not prove that the number belongs to a real card or account. It only means that the number has the right structure and no obvious typing mistake. Anyone can make up a number that passes the check.
Use the Luhn check as a typo filter. If a number is invalid, fix it before you send it anywhere. If it is valid, the real check still happens in the system that owns the number.
Where the Luhn check is used
Payment card numbers are the best known example. This is how a checkout form can say "invalid card number" before it contacts the bank. Some other identification numbers use the same check.
The Luhn check is fast and simple, and it catches typos before they cause problems. That is why forms run it first.
Ready to try it yourself?
Luhn‑validerare
Validera nummer med Luhn‑algoritmen.