Luhn Checksum Validator - Free, Instant, In Your Browser
Paste a card or ID number below to check it against the Luhn algorithm (a format/checksum check only - not a real payment verification).
How to use Luhn Checksum Validator
- 1Paste your text or data into the input box above.
- 2Luhn Checksum Validator runs instantly, right in your browser.
- 3Copy the result or use it directly.
Your file is processed in your browser and is never uploaded.
Frequently Asked Questions
What's the formula?
The Luhn algorithm doubles every second digit from the right, subtracts 9 from any result over 9, and checks that the total sum is a multiple of 10.
Is my data sent to a server?
No - everything runs entirely in your browser with JavaScript. Nothing is uploaded.