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Routing number validator

Checksum in your browser

Paste one or many US routing numbers to check the 9-digit ABA checksum and see the Federal Reserve district, or switch to EIN, ZIP, IBAN or card-number (Luhn) checks. Everything runs in your browser.

Try:
Paste up to 200; spaces and dashes are ignored. Nothing is sent or saved.
Drop a .txt or .csv file here, or· read in your browser, never uploaded
Runs in your browser. Ctrl+Enter also works.

Fill in the fields to see the result.

How to use it

  1. Pick the number type (routing number is selected).
  2. Paste numbers one per line, or drop a .txt or .csv file.
  3. See valid or invalid with the reason for each; download the results as CSV.

Details

ABA check
Digits weighted 3-7-1, sum divisible by 10; first two digits give the Federal Reserve district
Also checks
EIN prefix, ZIP and ZIP+4, IBAN mod-97, card Luhn, SSN format
Batch
Up to 200 numbers at once
Not checked
Whether a number was issued or is active; bank names are not shown

Questions

Does a valid result mean the routing number is real?

No. It means the number is well formed and its check digit is right. Only your bank or the Federal Reserve's E-Payments Routing Directory can confirm it belongs to a bank. A typo usually fails the checksum.

Why isn't the bank name shown?

The Federal Reserve's routing directory is not licensed for redistribution, so we only check the format. Your bank's website or a cheque shows the right routing number.

Is SSN checking safe?

Only the format is checked (area, group and serial rules), in your browser. Nothing is sent or saved, and the numbers are never put in the page address.

Can I check a whole list?

Yes: paste up to 200 lines or drop a file, then download a CSV with the result and reason for each.

Is what I type sent anywhere?

No. The calculation runs in this browser tab with the same code our MCP server uses. Nothing you type is sent to a server or saved, apart from settings like filing status, which stay in this browser.

Can an AI agent use this?

Yes. The same function is a tool on our free MCP server at tools.cuelark.com/mcp, so ChatGPT, Claude or Cursor get exactly the answer this page shows. 'Copy MCP call' gives you the arguments.