DigitProof API validates nine identifier types and suggests corrected check digits

DigitProof is a single API that checks the format and checksum of nine families of structured identifiers, including IBAN, LEI, ISIN, ISBN, GTIN, VIN, payment cards, UUID, and EU and GB VAT numbers. Beyond a simple valid or invalid result, it parses each identifier into its components and, when a checksum fails, reports the expected check digits along with a corrected identifier. The service performs only format and checksum validation and does not query bank directories or registries. It is stateless, stores no submitted values, and makes all endpoints available on the free tier, which allows 150 requests per month.