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What is an ISBN?
The International Standard Book Number (ISBN) is a 13-digit number that uniquely identifies books and book-like products published internationally.

What is the purpose of an ISBN?
The purpose of the ISBN is to establish and identify one title or one unique edition of a title from one specific publisher. An ISBN allows for more efficient marketing and cataloging of products by booksellers, libraries, universities, wholesalers, and distributors.

Do I really need an ISBN?
If you are selling your book on your own, you are not required to have an ISBN. However, if you want to sell your book online or in bookstores, place it with distributors and wholesalers, or put it in libraries, then you'll need to have an ISBN.

Can I get an ISBN for a book that isn't even written yet?
Yes, an ISBN can be assigned both to forthcoming and backlist titles, as well as ones that are currently in print.

Is an ISBN the same thing as a bar code?
This is a popular misconception. The bar code you see on the back of a book is derived from an ISBN, but the two are not the same. An ISBN is only a number. A bar code is a visual method used to convey an ISBN to a computer using scanning technology during a sales or inventory transaction process. An ISBN and a bar code are two different things.

What is the format of the ISBN?
Every ISBN consists of 13 digits, and whenever it is printed, it is preceded by the letters "ISBN". The 13-digit number is divided into five parts of variable length, each part separated by a hyphen, which makes it easier to read.

What is the significance of the numbers in an ISBN?
The five parts of an ISBN break down as follows:

1) The first three digits identify that it is an ISBN;

2) Identifies a country or group of countries;

3) Identifies a particular publisher within a geographic group;

4) Identifies a particular title or edition of a title;

5) A single digit at the end acts as a "check digit" to validate the ISBN.

What is a "check digit"? Why is the last digit sometimes "X"?
The check digit is derived from the other 12 digits using a complex algorithm. This helps to prevent errors that may normally result from mis-typing. The method of determining the check digit for the ISBN results in a number from 0 to 10, so the Roman numeral X is used whenever 10 would occur as a check digit.

What is an ISBN publisher prefix?
ISBNs are assigned to publishers in blocks of numbers: 10, 100, and 1,000. Each block is configured so that the first several digits are the same. These digits, called the prefix, are what identify a publishing company. When you submit an application for a block of ISBNs, you are applying for a "publisher prefix." When you have used up all of the ISBNs in your prefix, you will then apply for more ISBNs and be assigned a new prefix. It is not mathematically possible to add more ISBNs to a prefix.

What products are eligible for ISBNs?
ISBNs may be assigned to books and certain other items commonly found in bookstores. Non-book items eligible for ISBNs include e-books, audio books, calendars, bookmarks, software, greeting cards, and instructional and documentary DVDs and videos. ISBNs may never be assigned to music CDs, articles of clothing, foods, medicine, or stuffed animals, among other items.

Who can assign ISBNs to a publisher?
There are over 160 ISBN Agencies worldwide, and each ISBN Agency is appointed as the exclusive agent responsible for assigning ISBNs to publishers residing in their country or geographic territory. As the United States ISBN Agency, Bowker is the only source authorized to assign ISBNs to publishers supplying an address in the United States, U.S. Virgin Islands, Guam and Puerto Rico and its database establishes the publisher of record associated with each prefix.

How can I find an assigned ISBN?
The Publications (hard copy listings) in which the assigned ISBNs appear are Publishers, Distributors & Wholesalers of the United States, published by R.R. Bowker, and Literary Market Place, published by Information Today.