Skip to content
TextArray1.41.0
100% local

ISBN validator

Check ISBN-10 and ISBN-13 checksums, convert between formats, and format with hyphens.

Input
Output
Related tools
IBAN validatorNumbers
Credit card number checkerNumbers
Birth number validatorNumbers
Inline math evaluatorNumbers
Percent calculatorNumbers
Duration calculatorNumbers
ISBN validator
Paste one or more ISBNs — the 10-digit codes used before 2007 or the 13-digit codes used since — and this tool checks whether the final digit is a valid checksum, not just whether the number looks the right length. Use it to catch typos in a reading list, a library catalog import or a bibliography before you publish it, or to confirm a number printed on a book's back cover or copyright page actually adds up.
The output format option switches the result between hyphenated groups (978-0-306-40615-7) and a plain digit string, matching however you need to paste it elsewhere. Convert ISBN-10 to ISBN-13 or the other way round with the convert option — going from ISBN-13 to ISBN-10 only works for the original 978 prefix, since the newer 979 prefix has no 10-digit equivalent, and the tool says so rather than guessing. Turn on show publisher prefix to see the registration group and publisher segment of each number (978-0-306, for example) alongside the result, and turn on keep only valid numbers to strip everything else from a messy list down to just the numbers that check out.
Each line is treated as one ISBN, so a full reading list pastes in and validates in one pass. Windows and Unix line endings are both accepted, spaces and dashes inside a number are ignored while checking, and a line that isn't 10 or 13 digits at all is reported as not an ISBN rather than silently dropped. The live tally under the output counts how many lines validated and how many didn't.
Everything runs in your browser — no ISBN, book title or list you paste here is ever uploaded. Copy the result, download it as a .txt file, or send the output back into the input to apply another option pass.
FAQ
How does the checksum work?
ISBN-10 uses a weighted sum of its ten digits (with X allowed as the last digit for a value of 10) that must be a multiple of 11; ISBN-13 follows the same alternating-weight formula EAN-13 barcodes use, which must be a multiple of 10. A single wrong digit almost always breaks the checksum, which is what this tool checks.
Can every ISBN-13 convert to ISBN-10?
No. Only ISBN-13s starting with the original 978 prefix have a 10-digit equivalent. Numbers under the newer 979 prefix, opened once 978 ran low on capacity, exist only as ISBN-13, and the tool reports that instead of producing a wrong number.
What does the publisher prefix show?
It shows the registration group and, for the English-language group behind most 978-0 numbers, the exact publisher segment defined by the ISBN standard. For less common registration groups it falls back to a general two-digit split, since the full official range tables aren't built into an offline tool.
Does a valid checksum mean the book exists?
No. A valid checksum only means the number is well-formed — it doesn't confirm the ISBN was ever assigned to a real book. That requires looking it up in a publisher or library database.
Is my list uploaded anywhere?
No. ISBN validation runs entirely in your browser — the numbers you paste never leave your device.