Question 1

How does an ISBN check digit work?

Accepted Answer

ISBN-10 uses mod-11: each digit is multiplied by its position (10 down to 1), the sum is divided by 11, and the remainder becomes the check digit — with 'X' representing 10. ISBN-13 uses weighted mod-10: digits alternate between weight 1 and 3, the sum is rounded up to the next multiple of 10, and the difference is the check digit. Both algorithms are computed locally — no network calls.

Question 2

Can this tool convert ISBN-10 to ISBN-13 and back?

Accepted Answer

Yes. To convert ISBN-10 → ISBN-13 we prepend the 978 GS1 prefix, drop the ISBN-10 check digit, and recompute the ISBN-13 check digit. Reverse conversion (ISBN-13 → ISBN-10) only works when the prefix is 978; 979-prefixed ISBN-13s have no ISBN-10 equivalent because they belong to a newer allocation range that did not exist when ISBN-10 was the standard.

Question 3

How does the parser split an ISBN into prefix, group, publisher, title, and check digit?

Accepted Answer

We bundle the ISBN range message table published by the International ISBN Agency. After stripping the 978/979 prefix (ISBN-13 only) and the trailing check digit, we walk the registration group ranges (e.g. 0–5 = English-speaking, 2 = French, 3 = German) to identify the group, then walk the publisher ranges within that group to identify the publisher block. The remaining digits form the title identifier.

Question 4

Are my ISBNs uploaded to a server?

Accepted Answer

Never. Every check-digit computation, validation, conversion, and parse runs 100% client-side in your browser. There is no server endpoint, no analytics on the input field, and no logging of ISBN data. The history feature stores only operation metadata (counts + timestamps) in localStorage on this device — never the ISBNs themselves.

Question 5

What extra features does this tool have versus other ISBN tools?

Accepted Answer

(1) ISBN-10 mod-11 + ISBN-13 weighted mod-10 validate/generate. (2) ISBN-10 ↔ ISBN-13 conversion with 979-prefix edge handling. (3) Bundled ISBN range table for proper hyphenation. (4) Structural parser breaking ISBN into prefix/group/publisher/title/check. (5) Batch validate up to 5k rows. (6) Batch generate up to 1k ISBNs per click. (7) EAN-13 barcode render (text-art). (8) X check-digit handling for ISBN-10. (9) CSV export of batch results. (10) Deterministic seeded PRNG for reproducible test fixtures. (11) Format toggle (hyphenated vs raw). (12) localStorage history (max 20, no ISBNs stored). (13) Shareable URL with format + count + version encoded.

ISBN Generator & Validator

10 ISBNs

How to use

10 ISBNs