Is the ISBN validator free?

Yes, completely free with no signup and no usage limits.

Does my data leave my device?

No. All validation runs in JavaScript inside your browser. Nothing is sent to any server.

Does it work on mobile?

Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.

What is the difference between ISBN-10 and ISBN-13?

ISBN-10 is the older 10-digit format used for books published before 2007. ISBN-13 is the current international standard and always starts with 978 or 979. Most ISBN-10 numbers can be converted to ISBN-13 by prepending 978 and recalculating the check digit.

Why does my ISBN show as invalid?

The most common cause is a transcription error — a swapped or missing digit. The check digit (the last character) is a mathematical fingerprint of the preceding digits. Even a single wrong digit will fail the checksum.

ISBN Validator

Validate ISBN-10 and ISBN-13 numbers, check the checksum digit, and convert between formats.

100% client-side · no upload

Input

Output

How to use

Paste or type an ISBN-10 or ISBN-13 number (hyphens are ignored).
Click Validate — the checksum is checked and both ISBN-10 and ISBN-13 forms are shown.
Copy the result to use the canonical formatted ISBN.

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More ways to use this tool

Frequently Asked Questions

Is the ISBN validator free?: Yes, completely free with no signup and no usage limits.
Does my data leave my device?: No. All validation runs in JavaScript inside your browser. Nothing is sent to any server.
Does it work on mobile?: Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.
What is the difference between ISBN-10 and ISBN-13?: ISBN-10 is the older 10-digit format used for books published before 2007. ISBN-13 is the current international standard and always starts with 978 or 979. Most ISBN-10 numbers can be converted to ISBN-13 by prepending 978 and recalculating the check digit.
Why does my ISBN show as invalid?: The most common cause is a transcription error — a swapped or missing digit. The check digit (the last character) is a mathematical fingerprint of the preceding digits. Even a single wrong digit will fail the checksum.

Last updated: 2026-05-20 By jarvisbox