ABA Routing Number Structure Validator

This Actor performs offline structural analysis of user-supplied nine-digit US routing numbers. It checks the standard check digit, validates the routing prefix, identifies the four-digit Federal Reserve routing symbol, and maps ordinary bank/thrift/electronic prefixes to the corresponding Federal Reserve district.

It intentionally does not scrape or redistribute a routing directory. The Federal Reserve E-Payments Routing Directory restricts resale/relicensing/commercial use, and ABA's public lookup requires accepting terms and has strict daily/monthly lookup limits. The Actor does not accept those agreements for users, automate protected lookups, or substitute third-party bank identity claims.

Input

• routingNumbers — 1–100 unique values, each exactly nine ASCII digits and supplied as a string.
• maxItems — 1–100 output cap; default 20.

Output and meaning

Each record includes format/prefix/checksum findings, actual and expected check digit, routing symbol, category, optional Federal Reserve district, authoritative reference links, and explicit false flags for bank identity, active status, network eligibility, and operational approval.

structurallyValid: true means only that the digits are internally plausible. It does not prove that the number was issued, remains active, belongs to a named institution, supports checks/ACH/wires, matches an account, or is safe for a transaction. Confirm payment instructions directly with the financial institution or a licensed authoritative directory.

Safety and cost

The Actor makes no network requests during a run, processes at most 100 values in memory, and does not collect account numbers or personal data. Never submit bank account numbers; they are outside the schema and scope.

Development

Use Node.js 22 or newer. Run npm test, npm run check, and npm run validate. The bounded fixture contains two checksum-valid structures and one deliberate check-digit error.