CUSIP validation
CUSIP-9 North American security identifier — checksum: CUSIP mod-10 with digit summing. Free in your browser, or over the JSON API.
What it is
CUSIP-9 North American security identifier. CodeCheck verifies three things separately — format, length and check digit — and returns the expected and provided check digit, so a failed value tells you exactly what is wrong instead of just saying no.
Algorithm
CUSIP mod-10 with digit summing. The answer is derived from the value itself, with no database lookup and no third-party call, so it is deterministic, fast and privacy-safe.
Examples
| Value | Result | Expected | Provided |
|---|---|---|---|
| 037833100 | valid | 0 | 0 |
| 594918104 | valid | 4 | 4 |
API
curl "https://<your-worker>.workers.dev/v1/validate/cusip/037833100"
This type has a single trailing check digit, so CodeCheck can also compute it:
GET /v1/complete/cusip/{body}
Try it in the browser demo — the demo runs the same code offline.