ISBN Validator: Verify Book Numbers
Our ISBN validator checks if an International Standard Book Number is mathematically valid by verifying the check digit. It supports both ISBN-10 (10 digits) and ISBN-13 (13 digits) formats and can convert between them.
ISBN validation is essential for publishers, booksellers, and libraries to ensure accurate book identification. A single digit error can cause inventory problems or failed orders.
ISBN-10 vs ISBN-13
ISBN-10: The original format (1970-2007). 10 digits where the last is a check digit (0-9 or X, where X=10).
ISBN-13: Current format (2007+). 13 digits starting with 978 or 979. Compatible with EAN-13 barcodes.
All ISBN-10s can be converted to ISBN-13 (add 978 prefix), but only 978-prefix ISBN-13s convert back.
How Check Digits Work
ISBN-10: Multiply each digit by its position (10 down to 1), sum them, and the result must be divisible by 11.
ISBN-13: Multiply alternating digits by 1 and 3, sum them, and the result must be divisible by 10.
ISBN Structure
An ISBN consists of 5 parts: Prefix (978/979 for ISBN-13), Registration Group (country/language), Registrant (publisher), Publication (title), and Check Digit. Hyphens separate these parts for readability but are optional.
FAQ
Does a valid ISBN mean the book exists?
No. ISBN validation only checks mathematical validity. A passing check digit doesn't guarantee the book was published or that the ISBN was officially registered.
Why is X used in ISBN-10?
The modulo-11 check algorithm can produce 11 possible check digits (0-10). Since we need a single character, 10 is represented as X (Roman numeral for 10).