Verhoeff Damm Check
Compute and validate Verhoeff and Damm check digits for error-detecting numeric identifiers.
Verhoeff and Damm check digits for numeric IDs
Check digits catch typos in serial numbers, inventory labels, and government identifiers. The Verhoeff algorithm detects all single-digit errors and most adjacent transpositions. The Damm algorithm is a quasigroup-based alternative with similar guarantees.
Append vs validate
Choose Append check digit when you have a payload such as
2363 and need the full number including the check symbol. Choose
Validate when a user typed the entire string and you need a pass/fail
result.
For Luhn-based payment and GTIN barcodes, use the Luhn Algorithm Calculator or GTIN Check Digit Calculator.
Frequently Asked Questions
When should I pick Verhoeff over Luhn?
Verhoeff catches adjacent digit swaps that Luhn can miss. It is common in serial-number schemes where transposition errors are likely.
What is Damm used for?
Damm provides a single check digit with strong error detection and is used in some national ID and banking auxiliary schemes. Validation succeeds when the matrix checksum returns zero.
Are my numbers sent to a server?
No. Digits are processed entirely in your browser.
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