ISBN Validator
Check ISBN-10 and ISBN-13 numbers instantly.
How to use
- 1 Paste or type the ISBN, with or without dashes and spaces.
- 2 The tool detects whether it is an ISBN-10 or ISBN-13.
- 3 See whether the check digit is valid.
- 4 If it is invalid, read the expected check character and suggested correction.
- 5 Copy the cleaned digits for your records.
About ISBN Validator
The ISBN Validator checks whether a book number is well formed by recomputing its check digit, the built-in safeguard that catches typos and transposed characters.
It accepts both formats: the older ten-character ISBN-10, whose final position may be the letter X (standing for the value ten), and the modern thirteen-digit ISBN-13 that shares its checksum scheme with EAN-13 barcodes.
Dashes, spaces and the various hyphen characters publishers use are stripped automatically, so you can paste a number exactly as it appears on a copyright page or barcode.
ISBN-10 uses a weighted modulo-11 calculation, while ISBN-13 alternates weights of one and three under modulo-10; the tool applies the correct algorithm based on length and tells you the detected format.
When a number does not check out, it does not just say "invalid" — it shows the check character the number carries, the one it should have, and a corrected suggestion, which usually reveals a single mistyped or swapped digit.
Inputs that are the wrong length or contain illegal characters get a clear, specific message instead of a silent failure.
Everything runs locally in your browser with plain JavaScript: no lookups against a catalogue, no network requests and no data stored, so it works offline and keeps your queries private.
It is handy for librarians, booksellers, publishers and developers cleaning bibliographic data.
FAQ
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 is the ten-character format used until 2007 and can end in an X; ISBN-13 is the thirteen-digit format used today, matching the EAN-13 barcode. The validator handles both and detects which one you entered.
Why can an ISBN-10 end in the letter X?
The ISBN-10 check digit is computed modulo 11, so it can take a value of ten. Since ten is not a single digit, the letter X is used to represent it in the final position.
Does this confirm the book actually exists?
No. It only verifies that the number is mathematically valid via its check digit. It does not look the ISBN up in any catalogue, so no data leaves your browser.