✅ Luhn Check Validator — Card Number Checksum
Paste a number to test the Luhn checksum used by payment cards and some ID schemes. Spaces and dashes are ignored. Nothing is uploaded.
Input
Result
Details
Private by design. This tool runs entirely in your browser — nothing you enter or add is uploaded to any server.
How it works
- Spaces and dashes are stripped so only digits remain.
- The Luhn algorithm doubles every second digit from the right and sums the digits.
- A total divisible by 10 is valid. A brand hint is inferred from the prefix only.
Examples
- 4242424242424242 is a common Visa-format test number and passes Luhn.
- 4242424242424241 fails because the check digit is wrong.
- Dashes in 3782-822463-10005 are ignored before the checksum.
Frequently asked questions
Does a passing check mean the card is real?
No. Luhn only checks the checksum. It cannot confirm that an account exists, is funded, or is not stolen.
Is the number sent to a server?
No. The check runs in your browser and the field is not submitted anywhere.
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