The numbers
| Case | Rule |
|---|---|
| Paperback | free KDP ISBN or your own |
| Hardcover | its own ISBN, different from the paperback's |
| Kindle eBook | optional; Amazon assigns an ASIN |
| Low-content book | optional; not eligible for a free KDP ISBN |
| New edition with significant changes | a new ISBN |
| Free KDP ISBN outside KDP | not allowed |
| Imprint with a free KDP ISBN | Independently published |
| Imprint with your own ISBN | must match the ISBN's registration exactly (case and spaces included) |
| Expanded Distribution | the ISBN must not have been submitted for distribution through another service |
Free KDP ISBN or your own
The free KDP ISBN is the simplest option, but it is tied to KDP: it can't be used to publish the same edition anywhere else, and the book's imprint shows as "Independently published." Your own ISBN, bought from your country's ISBN agency (Bowker in the United States), lets you use your imprint name and publish the same edition through other printers.
With your own ISBN, the imprint you enter must match the agency's records exactly. KDP treats these fields as case-sensitive, and even a trailing space causes a mismatch.
ISBN and barcode
KDP prints the barcode on the back cover, in a 2 × 1.2 in white box, whether the ISBN is free or your own, unless your cover already includes one (see barcode area).
Example: one book, three formats
A picture book published as a paperback, a hardcover and a Kindle eBook needs two ISBNs, one per print format; the eBook can go without. If the author also wants to print the paperback through another printer, that edition needs an ISBN the author owns, because the free KDP ISBN can't leave KDP.
Common mistakes
- Reusing the paperback's ISBN for the hardcover.
- Using a free KDP ISBN for an edition printed elsewhere.
- Typing the imprint differently from the ISBN registration (case, spaces, punctuation).
- Trying to use a free KDP ISBN on a low-content book.
- Keeping the same ISBN for a new edition with significant changes.