ISBN validator
Validate an ISBN-10 or ISBN-13 number using its check digit.
🔒 100% client-side — no data sent
Check the validity of an ISBN-10 (mod 11 check digit) or ISBN-13 (EAN mod 10 check digit) by verifying its check digit. Perfect for catching a typo in a book reference. Calculation runs 100% in your browser: no data is sent to any server.
What is it for?
- ▸ Check an ISBN before adding it to a catalog
- ▸ Verify a book reference on an order
- ▸ Validate an ISBN-13 before generating an EAN barcode
- ▸ Spot a typo on the back cover
FAQ
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 (used until 2007) uses a mod 11 check; ISBN-13, aligned with the EAN barcode, adds a 978/979 prefix and a mod 10 check.
What does the "X" at the end of an ISBN-10 mean?
The X represents the check digit value 10 in the mod 11 calculation, which cannot be written as a single digit.
How is the ISBN-13 check digit calculated?
The digits are weighted alternately by 1 and 3, then the check digit brings the total up to the next multiple of 10.
Can an ISBN-10 be converted to ISBN-13?
Yes: you add the 978 prefix, drop the old check digit and recalculate the mod 10 check digit.