An ISBN is the number the book trade uses to tell one edition of one book from another: one number for the paperback, another for the hardcover, and up to two more for the ebook and the audiobook. Whether those last two need one at all depends on where you sell them, because some retailers require an ISBN before they will list a title while others issue their own catalogue number and never ask for one. An ISBN is not a copyright registration, and it is not the same thing as the catalogue number a retailer generates for its own store.
This guide gathers our posts on ISBNs and book barcodes in one place: what the number is, where to get one, how many your book needs, and what ends up printed on the back cover. Each post answers a single question and stands on its own, so start wherever your question sits rather than at the top. We add to the guide as we cover more ground, so it is worth bookmarking.
One caveat runs through all of it. The agency that issues ISBNs, what they cost, and whether they are free at all depend on the country you register in, so an answer that holds in the US may not hold in the UK, Canada or Australia. The International ISBN Agency keeps a directory of national ISBN agencies if you need to find yours.
What the number is
- ISBN-10 vs ISBN-13: what the two formats are, and whether you still need to know your ISBN-10.
- ASIN vs ISBN: what a retailer’s own catalogue number does, and why a print book ends up carrying both.
Where to get one
- Free ISBNs: what you give up when a platform supplies the number instead of you.
- Separate ISBNs for KDP and IngramSpark: whether one paperback can carry one number across both.
Whether you need one, and how many
- Selling without an ISBN: whether a book you sell yourself needs one, and why a printer might still ask.
- Audiobook ISBNs: when an audiobook needs its own number and when it does not.
- Revised editions: how much has to change before the book needs a fresh ISBN.
The barcode on the back cover
- ISBNs and barcodes: whether you have to buy the barcode as well as the number.
- The EAN-5 add-on: the second, smaller barcode beside the main one, and when it earns its place.