ISBN validator

The international standard book number (worldwide). Validation runs entirely on the check-digit algorithm: mod-11 for ISBN-10 and mod-10 weighted 1/3 for ISBN-13. No external registry is queried, so there is no rate limit and no per-lookup fee.

Result appears here.

What the API returns

GET /v1/identity/validate?type=isbn&value=978-3-16-148410-0

{
  "type": "isbn",
  "valid": true,
  "formatted": "978-3-16-148410-0",
  "details": { ... }
}

Important limitation, stated plainly

A checksum proves the number is well-formed. It does not prove the number was ever issued, nor that it belongs to the person presenting it. Any vendor claiming otherwise from a checksum alone is overselling. Use this to reject the ~90% of bad input that is simply mistyped, then use an official registry for the rest.