An ISBN (International Standard Book Number) is a unique identifier assigned to your book, allowing retailers, libraries, and distributors to track and sell it. Without an ISBN, your book may not be eligible for distribution through major platforms like Amazon, IngramSpark, and bookstores.

In addition to an ISBN, you’ll need a barcode, which encodes your book’s pricing information for retailers. Many self-publishing platforms provide ISBN registration services, or you can purchase one directly from an official ISBN agency. Ensuring your book has a registered ISBN and barcode is a key step in making it available for purchase.