An ISBN validator checks whether a book's International Standard Book Number has a valid check digit. It automatically detects ISBN-10 (older 10-digit format) and ISBN-13 (current 13-digit EAN format), strips formatting, verifies the mathematical check digit, and offers to convert between formats.
Hyphens and spaces are ignored. Accepts ISBN-10 or ISBN-13 in any formatting.
Validation Checks
ISBN Details
Validation Rules (ISBN-10 & ISBN-13)
ISBN-10 check digit: Multiply each of the first 9 digits by its position (d₁×10 + d₂×9 + ... + d₉×2), add the check digit. Total must be divisible by 11. Check digit can be 0-9 or X (=10).
ISBN-13 check digit: Multiply digits by alternating weights 1 and 3: (d₁×1 + d₂×3 + d₃×1 ... + d₁₂×3). Check digit = (10 − (sum mod 10)) mod 10. Always a digit 0-9.
ISBN-13 prefix: Must start with 978 or 979. The 979-10 prefix is used for French-language books; 978 covers all others.
Conversion: Any ISBN-10 can be converted to ISBN-13 by prepending "978" and recalculating the check digit. The reverse (ISBN-13 to ISBN-10) only works for 978-prefix ISBNs.
How to Use the ISBN Validator
The International Standard Book Number (ISBN) is a 10 or 13-digit identifier assigned to every commercially published book. A check digit embedded in the number allows anyone to verify that the ISBN was copied or transmitted correctly. This validator checks that check digit, detects the ISBN format, and can convert between ISBN-10 and ISBN-13.
Step 1: Enter the ISBN
Paste or type the ISBN in any format. You can include hyphens, spaces, or paste directly from a book cover or database. The tool strips all non-digit characters (except X for ISBN-10 check digits) before validation. Examples: 978-3-16-148410-0, 0-306-40615-2, or 9783161484100.
Step 2: Review the Checklist
The pass/fail checklist shows: correct digit count (10 or 13), all characters valid (digits only, except X at end of ISBN-10), valid EAN prefix for ISBN-13 (must start with 978 or 979), and whether the check digit is correct. The check digit test is the definitive pass/fail — all other checks are format prerequisites.
Step 3: Use the Conversion Feature
For valid ISBNs, the tool offers the equivalent in the other format. If you enter an ISBN-10 (like 0-306-40615-2), you'll see the ISBN-13 equivalent (978-0-306-40615-7). If you enter an ISBN-13 with 978 prefix, you'll see the ISBN-10. ISBN-13 numbers starting with 979 cannot be converted to ISBN-10 — those are the newer EAN-only assignments.
When is ISBN Validation Useful?
ISBN validation is useful when importing book metadata, building inventory systems, scraping book data from multiple sources, or verifying that a barcode scan captured the number correctly. A single digit transposition will always fail check digit validation, making this a reliable way to catch common scanning or typing errors before they propagate into a database.
FAQ
Is this ISBN validator free?
Yes, completely free. No signup, no account, no rate limits. All validation runs in your browser using JavaScript with no data sent to any server.
Is my ISBN data safe?
Yes. All validation runs entirely in your browser. No data is transmitted to any server. You can safely validate any ISBN number.
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 is the older 10-digit format used before January 2007. ISBN-13 is the newer 13-digit format (EAN-13) that replaced it. All ISBN-10 numbers can be converted to ISBN-13 by adding the '978' prefix and recalculating the check digit. New books published after 2007 only have ISBN-13.
How does ISBN check digit verification work?
ISBN-10 uses a weighted sum: multiply each digit by its position (1–10), sum them, and the result must be divisible by 11. The last digit can be X (representing 10). ISBN-13 uses alternating weights of 1 and 3, sums the first 12 digits, and the check digit equals (10 minus the sum mod 10) mod 10.
Can I enter ISBNs with hyphens or spaces?
Yes, the validator accepts any formatting. Hyphens, spaces, and dashes are stripped before validation, so you can paste ISBNs in any format: 978-3-16-148410-0, 9783161484100, or 978 3 16 148410 0 are all accepted.
Does this tool look up book information?
No. This tool validates the ISBN number's mathematical integrity only — it does not connect to book databases to retrieve title, author, or publisher information. For book lookups, use services like Open Library (openlibrary.org) or Google Books.