Publishing glossary
Free ISBN validator
Validate any ISBN and get the clean ISBN-13 form.
Paste an ISBN-10 or ISBN-13. The validator checks the check digit, converts to ISBN-13, and formats it for your metadata.
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What the check-digit math actually proves
An ISBN is not a random serial: the last digit is calculated from the first twelve. A transposed digit nearly always fails the check. Amazon, Ingram, and every retailer key the edition record by the whole number, so a bad ISBN either fails the lookup or points the store to someone else's book.
The validator converts ISBN-10 to the ISBN-13 form you need in KDP metadata, and it formats the number without stray spaces or hyphens so you can paste it straight into your listing.
- Retailer lookups use the literal string — keep it exact
- 978 and 979 prefixes are both valid; the check covers both
- An IBNS-style typo in your metadata is invisible until the store cannot find the edition
Before you paste it into the copyright page
Decide first whether you use Amazon's free KDP ISBN (perfectly fine in the KDP store) or a purchased ISBN that allows broad distribution elsewhere. The number itself does not change, but where it appears does: print editions need the ISBN in the copyright page; the ebook's ISBN is metadata only.
If a number already belongs to an existing edition — for example, a second edition of a book you published — do not reuse it. New content, changed trim size, or a re-issued format each need their own number. Keep one row in the metadata checklist for every ISBN you own.
FAQ
Frequently asked questions
What does the validator do if the number is invalid?
It marks the failed check digit and shows both the offending digit and the corrected ISBN-13, so you can fix the source instead of guessing which digit slipped.
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Put a verified ISBN on the copyright page.
Validate your number, then place it in the metadata checklist.