Validate ISBN-10 or ISBN-13 values and calculate the expected check digit.
Type
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Status
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Expected check
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Enter the example value or paste your own input, choose the mode when one is available, and read the first result card for the direct answer. The output area gives a copyable block for code reviews, documentation, API tests, classwork or troubleshooting notes.
What the result means
The tool strips hyphens and spaces, applies the ISBN-10 or ISBN-13 weighting rule, and reports the expected final digit.
What is not included
Checksum validation does not confirm that a book record exists or that the publisher metadata is current.
Privacy note
The calculation runs in your browser. Avoid pasting production secrets, credentials, private keys, customer data or regulated personal data unless your own policy allows browser-based tools.