ISBN Validator
Check whether a 10-digit or 13-digit ISBN's check digit is correct.
Overview
Every ISBN ends in a check digit computed from the digits before it — ISBN-10 uses a weighted sum mod 11 (where the check digit can be 'X' for 10), and ISBN-13 uses a weighted sum mod 10, the same scheme as EAN-13 barcodes. A typo in any single digit almost always breaks the checksum, which is how this tool catches mistyped or fake-looking ISBNs before you use them.
Examples & Sample Data
Valid ISBN-13
9780306406157
Valid ISBN-13
Valid ISBN-10
0306406152
Valid ISBN-10
How It Works
- Paste an ISBN, with or without hyphens or spaces.
- The tool detects whether it's 10 or 13 digits.
- It recomputes the check digit and reports whether the ISBN is valid.
Common Use Cases
Cataloging books
Confirm an ISBN was typed or scanned correctly before adding it to a library or store catalog.
Spotting fake or mistyped ISBNs
A listing with an invalid checksum is a signal the ISBN was mistyped or never assigned.
Tips & Best Practices
- Hyphens and spaces are ignored automatically — paste an ISBN exactly as printed on the book.
Frequently Asked Questions
No. Every check runs locally in your browser.
ISBN-13 replaced ISBN-10 in 2007 and is 3 digits longer with a '978' or '979' prefix; both use a different checksum formula, and this tool validates whichever length you enter.
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