What Is an ISBN?

ISBN stands for International Standard Book Number - a unique identifier assigned to each edition of every published book and book-like product.

The U.S. ISBN agency Website (www.isbn.org) defines an ISBN as follows: "The International Standard Book Number (ISBN) is a 10-digit number that uniquely identifies books and book-like products published internationally. The purpose of the ISBN is to establish and identify one title or edition of a title from one specific publisher and it is unique to that edition, allowing for more efficient marketing of products by booksellers, libraries, universities, wholesalers and distributors."

The Components of an ISBN

Until the change from 10- to 13-digit ISBNs takes place in January 2007, an ISBN is a 10-digit number that's divided by hyphens into four parts:

Part I: Identifies the country in which the ISBN is assigned.

Part II: Identifies the publisher to whom the ISBN was originally allocated. Keep in mind, however, that as publishers buy and sell various imprints (subsidiaries of a publishing house) or parts of imprints, this part of the ISBN becomes less and less reliable as a way to identify the publisher of the title. If one publishing house sells an imprint to another publishing house, this part of the ISBN doesn't change. Therefore, Part II of an ISBN can become meaningless in terms of identifying a book's current publisher.

Part III: Identifies the title.

Part IV: The check digit (the last digit in an ISBN). The check digit ensures that each ISBN is valid, meaning that the number is correct.

Parts II and III of an ISBN-10 vary in length as to how the numbers are grouped, but the total number of digits in an ISBN-10 is always 10.

ISBN-13s Are EANs

The goal of obtaining additional numbers for books could have been reached by changing the ISBN-10 to an 11-digit number rather than a 13-digit one. The 13-digit number was chosen, however, because by redefining the ISBN in this way, the number can become part of a larger system of identifiers called EAN. EANs are 13-digit identifiers assigned to all products available for retail sale worldwide. In short, using the 13-digit ISBN will make it easier to distribute and sell books worldwide. Note: In the beginning, EAN stood for European Article Number. Although the identifier is now officially named the International Article Number, it maintains the shortened moniker EAN.

EAN is the barcode number on the back of books, now known as the "International Article Number." This 13-digit number has been in use for years in the retail trade.

If you look closely at the ISBN-10 and the barcode number on the back of a book, you will see they are mostly the same. The ISBN-10 simply has a 978 in front of the first nine digits.

The 10th digit of an ISBN is the check digit. A new check digit is required for the ISBN-13.

All books will have 978 or 979 as their first three EAN/ISBN-13 numbers. The official standard for this is ISO 2108:2005. Any ISBN-13 with a 978 prefix can be converted into an ISBN-10, however, there is no ISBN-10 equivalent for a book with a 979 prefix.

Dual numbering

The Book Industry Study Group (BISG) decided early in the process that the move to ISBN-13 should be a phased transition rather than an abrupt cutover. Thus, organizations in the book industry are urged to proceed with the change - but somewhat at their own pace. During the transition period, for example, one of the primary recommendations is that both human-readable ISBN-10s and ISBN-13s be used whenever possible. We call this practice dual numbering.

For more information on ISBN-13, you can visit the Book Industry Study Group ISBN-13 information page.