NPI Validator
Check whether a 10-digit number is a well-formed National Provider Identifier. The validator recomputes the NPI check digit (a Luhn checksum over the first nine digits, prefixed with the health-industry namespace 80840) and compares it to the tenth digit.
Runs entirely in your browser — nothing is sent anywhere.
What this checks (and what it doesn’t)
A passing result means the number is structurally valid — the kind of quick check a billing system runs to catch typos and digit transpositions. It does not confirm the NPI is actually assigned to a provider. To confirm that, look it up in the registry.