ISBN Validator & Converter
ValidatorValidate ISBN-10 and ISBN-13 book identifiers and convert between formats. Instant check digit verification. Free, runs entirely in your browser.
ISBN (International Standard Book Number) is a unique numeric identifier for books and similar publications. Managed by the International ISBN Agency, every new book published commercially receives an ISBN that identifies it globally — enabling libraries, bookstores, and distributors to uniquely track and order any title.
The original ISBN-10 format (1970–2007) uses 10 characters including a Mod-11 check digit. The current ISBN-13 format (2007–present) aligns with the EAN-13 barcode system and uses 13 digits with a Mod-10 check digit. The transition means every ISBN-10 has an equivalent ISBN-13 (by prepending '978'), but the reverse is only true for books originally in the 978 prefix.
| Format | Length | Check Digit | Example |
|---|---|---|---|
| ISBN-10 | 10 chars | Mod 11 (0–9 or X) | 0-306-40615-2 |
| ISBN-13 | 13 chars | Mod 10 (0–9) | 978-0-306-40615-7 |
About this tool
About ISBN Validator & Converter
ISBN (International Standard Book Number) is the universal identifier for books and book-like products. ISBN-10 (the original 1970 format) uses 10 characters with a Mod-11 check digit that can be the letter X. ISBN-13 (the current format, in use since 2007) uses 13 digits with a Mod-10 check digit and always starts with the prefix 978 or 979. All ISBN-10 numbers can be converted to ISBN-13; only those starting with the 978 prefix can be converted back to ISBN-10.
This validator strips all spaces and hyphens before checking, auto-detects whether the input is ISBN-10 or ISBN-13 from its length, verifies the check digit using the correct algorithm for each format, and when the ISBN is valid automatically computes and displays the converted version (ISBN-10 → ISBN-13, ISBN-13 → ISBN-10 when the prefix allows).
ISBN validation is essential for bookstore inventory systems, library catalogues, e-commerce product databases, publishing workflows, and any application that ingests book metadata. Use this tool to verify ISBNs before insertion into a database, to convert between formats for API compatibility, or to debug why a book lookup is failing.
Instant validation with no network requests — the check digit is computed locally in the browser. The tool handles all common input formats (with or without hyphens or spaces), so you can paste directly from a book's copyright page, barcode scanner, or library export.
Key Features
- Validates both ISBN-10 and ISBN-13
- Auto-detects format from input length
- Strips hyphens and spaces before checking
- Converts ISBN-10 ↔ ISBN-13 on valid input
- Shows formatted version with correct hyphenation
- Precise error messages: wrong length vs. wrong check digit
- 100% browser-based, no network requests
FAQ
ISBN Validator — Frequently Asked Questions
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 (introduced in 1970) uses 10 characters — 9 data digits plus a Mod-11 check character (0–9 or X). ISBN-13 (introduced in 2007) uses 13 digits — 12 data digits plus a Mod-10 check digit. ISBN-13 always starts with 978 or 979. All ISBN-10s correspond to an ISBN-13 starting with 978; the 979 prefix has no ISBN-10 equivalent. Since 2007, ISBN-13 is the mandatory standard; ISBN-10 is deprecated but still widely used in older databases and APIs.
How does the ISBN check digit work?
For ISBN-10: multiply each of the first 9 digits by weights 10, 9, 8, ..., 2; sum the products; compute (11 − sum mod 11) mod 11. If the result is 10, the check digit is X. For ISBN-13: multiply alternating digits by 1 and 3; sum the products; check digit = (10 − sum mod 10) mod 10. The check digit ensures any single-digit error or transposition produces a detectable mismatch.
How do I convert ISBN-10 to ISBN-13?
Prepend '978' to the first 9 digits of the ISBN-10 (discarding the ISBN-10 check digit), then compute a new ISBN-13 check digit using the Mod-10 algorithm on those 12 digits. Example: ISBN-10 0-306-40615-2 → prefix '978' + '030640615' = '978030640615', new check = 7, result = 978-0-306-40615-7.
Can every ISBN-13 be converted back to ISBN-10?
No. Only ISBN-13s that start with the 978 prefix can be converted to ISBN-10. The 979 prefix (used for new books published after the ISBN-13 standard took effect) has no ISBN-10 equivalent. This validator automatically shows the ISBN-10 conversion only when the 978 prefix is present.
Why does ISBN use hyphens?
The hyphens in an ISBN group its components: for ISBN-13, they separate the prefix (978/979), registration group (country/language area), registrant (publisher), publication, and check digit. For ISBN-10, they separate the group, publisher, title, and check digit. The grouping varies by country and publisher, so hyphen placement isn't mechanically predictable — it requires a lookup table. This validator shows a simplified hyphenation based on standard ranges.
What is the X in some ISBN-10 numbers?
The X in an ISBN-10 check position represents the value 10. Because the ISBN-10 check digit algorithm uses Mod 11 (which can produce values 0–10), and 10 cannot be represented as a single digit, the Roman numeral X is used instead. For example, ISBN-10 0-19-852663-6 ends in a digit, while 0-8044-2957-X ends in X because the Mod-11 result is 10.
Tips
- Paste an ISBN with or without hyphens and spaces — the validator strips them automatically
- If you have a barcode scanner, it outputs the 13-digit EAN which is the same as ISBN-13
- ISBN-10 ending in X is valid — X represents the value 10 in the Mod-11 algorithm
- 979-prefixed ISBN-13s cannot be converted to ISBN-10 — this is expected, not an error