Luhn Checksum Validator
Validate any number with the Luhn algorithm — cards, IMEIs, and account numbers.
Runs locally in your browser. Your input is not uploaded.
How to Use
- 1
Enter numbers
One per line — spaces and dashes are ignored.
- 2
Read the verdicts
Pass/fail with digit count, and the expected check digit on failure.
- 3
Use for any Luhn scheme
Cards, IMEIs, references — the algorithm is the same.
Frequently Asked Questions
- A mod-10 checksum from 1954: doubling every second digit from the right (subtracting 9 when over 9) and requiring the sum to end in 0. It catches every single-digit typo and most adjacent transpositions.
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