NPI Validator
Length, leading digit and check digit (Luhn with the 80840 prefix).
Clinical safety notice: Zero real patient data (PHI/PII) may be entered into this browser utility. Use synthetic test payloads only. Local-first deterministic processing; nothing leaves your browser.
How it works
An NPI is ten digits whose first digit is 1 or 2 and whose last digit is a Luhn check digit calculated over the nine leading digits preceded by the constant 80840. The tool recomputes the check digit and compares it with the tenth digit; for a failure it shows the digit that would have been correct. Spaces and hyphens are stripped and reported. The check proves only that the number is well formed: it does not show that the NPI is assigned, active or belongs to a given provider, which needs the NPPES registry. The leading digit does not indicate individual or organization.
Operational disclaimer. Results reflect deterministic parsing of user-provided datasets; verify against institutional standards and regulatory frameworks.
Deterministic local--first client-side execution; data transmission is zero. Provided as-is without warranty under the 1% value-saved licensing model.