[2] A different ISBN is assigned to each separate edition and variation of a publication, but not to a simple reprinting of an existing item.

The first version of the ISBN identification format was devised in 1967, based upon the 9-digit Standard Book Numbering (SBN) created in 1966.

In 1965, British bookseller and stationers WHSmith announced plans to implement a standard numbering system for its books.

[1] They hired consultants to work on their behalf, and the system was devised by Gordon Foster, emeritus professor of statistics at Trinity College Dublin.

[3] Since 2016, ISBNs have also been used to identify mobile games by China's Administration of Press and Publication.

For example, an ebook, audiobook, paperback, and hardcover edition of the same book must each have a different ISBN assigned to it.

Figuring out how to correctly separate a given ISBN is complicated, because most of the parts do not use a fixed number of digits.

The ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned, and so the ranges will vary depending on the number of books and the number, type, and size of publishers that are active.

Some ISBN registration agencies are based in national libraries or within ministries of culture and thus may receive direct funding from the government to support their services.

[42] Books published in rare languages typically have longer group elements.

[43] Within the 979 prefix element, the registration group 0 is reserved for compatibility with International Standard Music Numbers (ISMNs), but such material is not actually assigned an ISBN.

[44] The registration groups within prefix element 979 that have been assigned are 8 for the United States of America, 10 for France, 11 for the Republic of Korea, and 12 for Italy.

By using variable block lengths, registration agencies are able to customise the allocations of ISBNs that they make to publishers.

The ISBN check digit method therefore ensures that it will always be possible to detect these two most common types of error, i.e., if either of these types of error has occurred, the result will never be a valid ISBN—the sum of the digits multiplied by their weights will never be a multiple of 11.

However, if the error were to occur in the publishing house and remain undetected, the book would be issued with an invalid ISBN.

The value of the check digit is simply the one number between 0 and 10 which, when added to this sum, means the total is a multiple of 11.

Alternatively, modular arithmetic is convenient for calculating the check digit using modulus 11.

Repeatedly adding t into s computes the necessary multiples: The modular reduction can be done once at the end, as shown above (in which case s could hold a value as large as 496, for the invalid ISBN 99999-999-9-X), or s and t could be reduced by a conditional subtract after each addition.

Each digit, from left to right, is alternately multiplied by 1 or 3, then those products are summed modulo 10 to give a value ranging from 0 to 9.

However, 19 and 9 are congruent modulo 10, and so produce the same, final result: both ISBNs will have a check digit of 7.

[53] For example, ISBN 0-590-76484-5 is shared by two books—Ninja gaiden: a novel based on the best-selling game by Tecmo (1990) and Wacky laws (1997), both published by Scholastic.

Most libraries and booksellers display the book record for an invalid ISBN issued by the publisher.

In other words, each of the three separate EPUB, Amazon Kindle, and PDF formats of a particular book will have its own specific ISBN.

They should not share the ISBN of the paper version, and there is no generic "eISBN" which encompasses all the e-book formats for a title.

[56] The barcodes on a book's back cover (or inside a mass-market paperback book's front cover) are EAN-13; they may have a separate barcode encoding five digits called an EAN-5 for the currency and the recommended retail price.

Part of the 979 prefix is reserved for use with the Musicland code for musical scores with an ISMN.

Because the GTIN-13 is part of the Global Trade Item Number (GTIN) system (that includes the GTIN-14, the GTIN-12, and the GTIN-8), the 13-digit ISBN falls within the 14-digit data field range.

Hence, many booksellers (e.g., Barnes & Noble) migrated to EAN barcodes as early as March 2005.

The upgrading of the UPC barcode system to full EAN-13, in 2005, eased migration to the ISBN in North America.