2s.io

● healthy general

Validate a US bank ABA routing number with the Federal Reserve weighted mod-10 checksum (3-7-1) — not just a 9-digit regex. Returns {valid, routingNumber, district (routing-symbol class), reason}. Catches transposed digits in ACH/wire setup that a length check misses. Structure + checksum only; not a bank-directory existence lookup. -- reliability 91.0/100 per Paygent Discover

How to call

cURL · x402-fetch / x402-axios will auto-handle 402

curl -X POST https://2s.io

/.well-known/x402.json

https://2s.io/.well-known/x402