Validate an ID’s check character

About this check-character validator

A check character (also called a check digit) is the last character of an identifier, computed from the rest of the ID. When a participant, specimen, patient or product ID is mistyped, the check no longer matches and the error is caught before the record is saved. This page recomputes the check character in your browser and compares it with the one in the ID. Nothing is uploaded, so it is safe to use on real identifiers.

What each mode does

• Single checks one ID and shows which check character the algorithm expected. Two buttons introduce a typo or transpose two characters so you can watch the check catch them.
• Batch checks up to 1,000 IDs pasted from a spreadsheet or export, one per line.
• All algorithms runs one ID through every supported algorithm, which tells you which one an ID was issued under.
• Compute check adds the check character to a bare identifier so you can complete IDs by hand or in a script.
• Stress test injects every classic transcription error into a valid ID (single-character substitutions, adjacent and jump transpositions, twin errors) and reports how many each algorithm catches.

Supported algorithms

The same engine that issues IDs verifies them, so every algorithm below is available in both places: aba_mod10, damm, gs1_mod10, iso7064_letters1, iso7064_letters2 (2 characters), iso7064_mod11_10, iso7064_mod11_2, iso7064_mod37_2, iso7064_mod37_36, iso7064_mod97_10 (2 characters), luhn, mrz_mod10, verhoeff, weighted_mod11. ISO 7064 Mod 37,36 is the default because it works on letters and digits and catches every single-character error and every adjacent transposition.

Generating IDs that already carry a check character

Validation only catches errors after the fact. IDMinter generates IDs with the check character built in, keeps a ledger so two sites can never issue the same ID, and prints QR label sheets for them. How it works →