ISBN Validator & Lookup
Paste an ISBN to check it is valid, see its ISBN-13 form, and look the book up on Open Library. Built for bookshops, students and sellers in Nepal.
How it works
Paste an ISBN-10 or ISBN-13 (hyphens are optional).
Read whether the checksum is valid and its ISBN-13 form.
Optionally look the book up on Open Library for title and author.
Why use this tool?
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Validation uses the official ISBN checksum and needs no network - it works offline.
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ISBN-10 uses a modulo-11 check; the final digit may be X for 10.
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ISBN-13 uses a modulo-10 weighted (1,3,1,3…) check and almost always starts with 978 or 979.
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The Open Library lookup needs an internet connection; if it is blocked, validation still works.
Frequently asked questions
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 is the older 10-digit standard; ISBN-13 is the current 13-digit standard (usually prefixed 978 or 979). This tool validates both and converts a valid ISBN-10 to its ISBN-13 form.
Why does my ISBN say invalid?
A single mistyped digit breaks the checksum. Re-check the number - the last digit is a check digit, not part of the book code.
Does the lookup store my ISBN?
No. The lookup is a direct request from your browser to Open Library; nothing is saved on our servers.
Can I validate a Nepali book ISBN?
Yes - ISBNs are international. Any valid ISBN-10 or ISBN-13 from any country validates the same way.
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