ABA Routing Number API
US bank ABA routing-number (routing transit number) validation as an API, computed locally and deterministically. The validate endpoint checks a nine-digit routing number with the official ABA checksum — 3·(d1+d4+d7) + 7·(d2+d5+d8) + (d3+d6+d9) must be a multiple of ten — ignoring hyphens and spaces, and reads the first two digits as the Federal Reserve routing symbol to name the district (01–12 are the twelve Federal Reserve Banks from Boston to San Francisco, 21–32 are thrift institutions); JPMorgan Chase’s 021000021 validates and resolves to the Federal Reserve Bank of New York, and a number with a wrong check digit is rejected. The checkdigit endpoint computes the ninth check digit from the first eight so the whole number passes. It also returns the institution identifier (digits 5–8) and the check digit. Everything is computed locally and deterministically, so it is instant and private. Ideal for fintech, banking, ACH, payroll, payment and accounting app developers, bank-account-form validation and onboarding tools, and US payment software. This is the checksum and routing-symbol structure only — it does not confirm a live bank. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 2 endpoints. For SWIFT/BIC codes use a BIC API and for IBANs an IBAN API.
api.oanor.com/routingnumber-api
