Luhn checksum: valid Check digit for this prefix: 6 Detected scheme: Visa
About Luhn Algorithm Validator & Check Digit Calculator
The Luhn algorithm (also called the "mod 10" checksum) is a simple formula used to catch accidental errors in identification numbers. Credit and debit cards, IMEI device serials, some national IDs, and many account numbers append a check digit computed with Luhn, so a single mistyped or transposed digit can be detected before the number is processed.
This free Luhn validator tells you instantly whether a number passes the checksum, computes the check digit that completes a partial number, and makes a best-effort guess at the card scheme (Visa, Mastercard, Amex, Discover) from its prefix and length.
Everything runs entirely in your browser — no number is ever uploaded or stored. Note that the Luhn check only verifies the checksum's internal consistency; it does not confirm that a card is real, active, or belongs to anyone.
Features
- Validate any number against the Luhn (mod 10) checksum
- Compute the check digit that makes a partial number valid
- Best-effort card scheme detection (Visa, Mastercard, Amex, Discover)
- Spaces and dashes are ignored; works completely offline
How to use
- Type or paste the number into the input pane — spaces and dashes are fine.
- Read the Valid / Invalid badge to see if it passes the Luhn checksum.
- Check the computed check digit and the detected card scheme in the output.
Frequently asked questions
Does a valid Luhn result mean the card is real?
No. The Luhn algorithm only validates the checksum — it confirms the digits are internally consistent and catches typos. It cannot tell you whether a card actually exists, is active, has funds, or belongs to anyone. Only the card issuer can confirm that.
What is a check digit?
The check digit is the final digit of a Luhn-protected number. It is calculated from all the preceding digits so that the whole number satisfies the mod 10 checksum. This tool can compute that digit for you from a partial number.
Why do spaces and dashes not matter?
Card numbers are often written in groups (e.g. 4111 1111 1111 1111) for readability. The validator strips spaces and dashes before checking, so you can paste a number in any common format. Letters or other characters make the input invalid.
Is my number sent anywhere?
No. All validation and check-digit math happens locally in your browser. Nothing you type leaves your device, which is exactly what you want when working with sensitive numbers.
Related tools
Everything runs locally in your browser — your input is never uploaded.