Summary: how to use an ISBN validator free and privately
An ISBN validator checks whether an International Standard Book Number is well formed by recalculating its check digit. To check one, type or paste the number into the box above and press Validate. The check runs in your browser: the number is not uploaded, and you can confirm that in the Network tab of your browser's DevTools. You get a verdict, the correct check digit, both ISBN forms, the hyphenated number and an EAN-13 barcode you can download as SVG.
A valid result means the digits are consistent and the number lies in a range the International ISBN Agency has assigned. It does not prove that a publisher issued the number to a real book. Only the optional Look up on Open Library button contacts another site, and only when you click it.
Every ISBN-13 is also an EAN-13 number, so the tool draws the barcode on a book's back cover; other symbologies are in the barcode generator. Other check-digit schemes have their own tools: the credit card validator and the IBAN validator.
ISBN-10 compared with ISBN-13
| Property | ISBN-10 | ISBN-13 |
|---|---|---|
| Length | 10 characters | 13 digits |
| In use | 1970 to 2006 | Since 1 January 2007 |
| Prefix | None | 978 or 979 |
| Check rule | Weights 10 to 1, sum divisible by 11 | Weights 1, 3, 1, 3 and so on, sum divisible by 10 |
| Check digit | 0 to 9, or X for 10 | 0 to 9 |
| Worked example | 0-306-40615-2: weighted sum 132 = 12 × 11 | 978-0-306-40615-7: weighted sum 100 = 10 × 10 |
Both rules catch every single wrong digit. The ISBN-10 rule also catches every swap of two neighbouring digits. The ISBN-13 rule misses a swap only when the digits differ by exactly 5, such as 1 and 6, so a pass is strong evidence, not a guarantee.
Table of Use: what you enter and what you get
| You enter | What the tool reports |
|---|---|
| 0-306-40615-2 | Valid ISBN-10. ISBN-13 978-0-306-40615-7, registration group 978-0 (English language). |
| 978-0-306-40615-7 | Valid ISBN-13. ISBN-10 equivalent 0-306-40615-2. |
| 9780306406156 | Not a valid ISBN-13: the last digit is 6, but the first twelve digits need 7. |
| 0-306-4X615-2 | Not valid: X is only allowed as the last character of an ISBN-10. |
| 5901234123457 | Not valid: it starts with 590, not 978 or 979, so it is probably another kind of EAN-13 product barcode. |
| 9790060115615 | Not an ISBN: 979-0 is the ISMN (printed music) range. |
| 9791090636071 | Valid ISBN-13 979-10-90636-07-1, group France. No ISBN-10 exists for a 979 number. |
| A pasted list of ISBNs | Batch Validation: a valid count, hyphenated ISBN-13 and ISBN-10 for each row, and a CSV file. |
Features
- Check-digit validation for ISBN-10 (modulo 11, with X) and ISBN-13 (modulo 10), with a specific message for each failure: wrong check digit, wrong length, an impossible character or a misplaced X.
- Forgiving input. Hyphens, spaces, other dash characters, an "ISBN" or "ISBN-13:" label and invisible characters from copied web text are stripped before checking.
- ISBN-10 and ISBN-13 conversion in both directions, with one-click copy of either form without hyphens.
- Hyphenation by official ranges. The number is split into prefix, registration group, registrant, publication and check digit using the International ISBN Agency range table dated 5 October 2026, and the group is named, such as France.
- Unassigned ranges flagged. A correct check digit in a range not yet issued is marked as not a valid ISBN and is not counted as valid.
- EAN-13 barcode drawn for every valid ISBN, downloadable as an SVG file.
- Optional book details (title, author, publisher, date, pages, subjects, cover) from Open Library, a community-edited catalogue, when you ask for them.
- Batch mode for up to 5,000 numbers, with a CSV of every entry, its verdict and both hyphenated forms. Spreadsheet formula characters at the start of a cell are neutralised.
Tidy a list first with remove duplicate lines or sort lines alphabetically, and count entries with the line counter.
How to Use the ISBN Validator
- Stay on Single ISBN and click the field labelled "ISBN-10 or ISBN-13". Type or paste the number, or click one of the Try an example titles to see a finished result.
- Press Validate (or Enter). Read the headline, the check-digit badge and, for a valid number, the ISBN structure panel.
- Use Copy next to ISBN-10 or ISBN-13 to take either form. Press Download SVG under the EAN-13 barcode if you need the symbol as a file. To print product labels with an EAN-13 barcode, use the label generator.
- Press Look up on Open Library only if you also want the title, author and cover.
- For many numbers, choose Batch Validation, paste them into the box, press Validate All, then use Copy valid as ISBN-13 or Download CSV. The CSV opens in any spreadsheet application.
If a number fails, compare the calculated check digit in the red badge with what you typed, then check the number against the book itself rather than adjusting digits until the tool says valid.
Who Can Use It
- Self-publishers and small presses confirming the number on a cover file or distributor form has no typo before printing.
- Booksellers, librarians and archivists cleaning catalogue exports and converting old ISBN-10 records to ISBN-13.
- Students and researchers checking an ISBN before it goes into a reference list, or making a QR code for a handout.
- Developers and data teams testing import code: the examples above work as test cases, and find and replace cleans a column before checking.
FAQs
How do I check whether an ISBN is valid?
Recalculate the check digit from the other digits and compare it with the last one. For an ISBN-10, weight the digits 10 down to 1 and the sum must divide by 11. For an ISBN-13, weight them 1, 3, 1, 3 and so on, and the sum must divide by 10. Pressing Validate does this and also checks the number is in an assigned range.
Does a valid ISBN mean the book exists?
No. A valid result means the check digit matches and the number lies in a range the International ISBN Agency has assigned. It cannot show that a publisher actually used that number. The optional Open Library lookup shows whether a catalogue knows the book, but a missing record does not make an ISBN invalid.
How do I convert an ISBN-10 to an ISBN-13, and back?
To go from ISBN-10 to ISBN-13, put 978 in front of the first nine digits and calculate a new check digit with the ISBN-13 rule. For example 0-306-40615-2 becomes 978-0-306-40615-7. To go back, drop the 978 and the old check digit and calculate a modulo-11 digit. Only ISBN-13s starting 978 can be converted back, because 979 numbers never existed as ISBN-10s.
Why does it say the check digit is correct but the range is not assigned?
The last digit fits the other digits, but the number lies outside every range the International ISBN Agency had issued to a country or publisher in its 5 October 2026 table. That usually means a typo that happened to keep the check digit consistent. Numbers beginning 979-0 get their own message: they are ISMNs for printed music, not ISBNs.
Why is there an X at the end of some ISBN-10s?
The ISBN-10 check digit is calculated modulo 11, so it can be any value from 0 to 10. The value 10 is written as the Roman numeral X so the check digit stays one character. X can only appear in that last position of an ISBN-10, never earlier, and never in an ISBN-13, whose check digit is always 0 to 9.
Where do the hyphens in an ISBN go?
Hyphens separate the prefix, the registration group (a country or language area), the publisher, the title number and the check digit. Those parts vary in length, so positions cannot be guessed. The tool places them using the International ISBN Agency range table dated 5 October 2026. Hyphens are optional when you type an ISBN, and the Copy buttons copy the digits without them.
Is it safe to enter an ISBN here, and is it sent anywhere?
Validation, conversion, hyphenation and the barcode all run in your browser, and nothing you type is uploaded; the Network tab in DevTools will show no request for it. The one exception is the Look up on Open Library button: only when you click it does your browser request the ISBN-13 from openlibrary.org, which sees your IP address like any website.
Can I validate a list of ISBNs at once?
Yes. Open Batch Validation, paste up to 5,000 ISBNs separated by new lines, commas, semicolons or tabs, and press Validate All. Each entry is checked, hyphenated and converted. The table shows the first 500 rows, Copy valid as ISBN-13 copies every valid number, and Download CSV saves all results, including entries that failed.