ISSN validation
ISSN-8 serial publication number — checksum: ISSN mod-11 (weights 8..2). Free in your browser, or over the JSON API.
What it is
ISSN-8 serial publication number. 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
ISSN mod-11 (weights 8..2). 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 |
|---|---|---|---|
| 03785955 | valid | 5 | 5 |
API
curl "https://<your-worker>.workers.dev/v1/validate/issn/03785955"
This type has a single trailing check digit, so CodeCheck can also compute it:
GET /v1/complete/issn/{body}
Try it in the browser demo — the demo runs the same code offline.