ISBN validation

What it is

ISBN-10 or ISBN-13 book 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

ISBN-10 mod-11. 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

API

curl "https://<your-worker>.workers.dev/v1/validate/isbn/0306406152"

This type has a single trailing check digit, so CodeCheck can also compute it:

GET /v1/complete/isbn/{body}

Try it in the browser demo — the demo runs the same code offline.

Other identifier types