ISBN Validator
Check book ISBNs and convert between ISBN-10 and ISBN-13.
| Input | Valid? | ISBN-13 | ISBN-10 | Note |
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How it works
ISBN-10 uses a weighted sum modulo 11 (the last digit can be X, meaning 10); ISBN-13 uses alternating weights 1 and 3 modulo 10, like EAN barcodes. Every ISBN-10 has an ISBN-13 equivalent: add 978 in front and recompute the check digit. ISBNs starting with 979 have no ISBN-10 form.