ABA Routing Number Validator
Check a US bank routing number's 9-digit checksum and read its Federal Reserve district — entirely in your browser.
What's being checked
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A valid routing number is 9 digits and passes the 3-7-1 weighted checksum.
A US ABA routing transit number identifies the bank in a transfer — the role an IBAN's country+bank portion plays elsewhere (the US doesn't use IBAN). It's 9 digits: a 4-digit Federal Reserve routing symbol, a 4-digit institution identifier, and a final check digit.
This checks the length and the 3-7-1 weighted checksum the Federal Reserve uses, and reads the Fed district from the first two digits. It doesn't name the specific bank yet — that needs the Fed's participant directory, a larger dataset that can come later. Everything runs locally; nothing is sent anywhere.