ISBNs

ISBN stands for International Standard Book Number. It is a unique identifier assigned to a book edition and format, such as hardcover, paperback, or ebook. ISBNs facilitate cataloging, ordering, inventory management, and sales data for publishers, booksellers, and libraries. They are issued by national or regional ISBN agencies under the authority of the International ISBN Agency.

Two related standards exist: ISBN-10 and ISBN-13. ISBN-10, introduced in 1970, uses 10 digits with a check digit that may be a numeral or the letter X. ISBN-13, introduced in 2007 to align with the EAN-13 barcode system, uses 13 digits and a check digit calculated with alternating weights of 1 and 3. The 13-digit form often starts with the prefix 978 or 979, followed by a registration group (country or language), a registrant (publisher), a publication (title edition) number, and the final check digit.

A single title can have multiple ISBNs if there are separate editions or formats (for example, a hardcover, a paperback, and an ebook each receive their own ISBN) but the same content in the same format is identified by a single ISBN. ISBNs are typically included on copyright pages and barcodes, and they help libraries, retailers, and distributors track titles, manage catalogs, and collect bibliographic and sales data.

Conversion between forms is possible: existing ISBN-10 numbers can be expressed as ISBN-13 by prefixing with 978 and recalculating the check digit, then omitting the original ISBN-10’s check digit.