International Standard Book Number

The ISBN originated from the Standard Book Numbering (SBN) system developed in the United Kingdom in 1966 by the bookseller W.H. Smith and the British publisher J. Whitaker & Sons. The SBN was a 9-digit code, and in 1970 the International Organization for Standardization adopted it as ISO 2108, creating the 10-digit ISBN. The 10-digit format was used until 2007, when the system transitioned to 13 digits to align with the EAN-13 barcode system, expanding the available number space. The change was managed by the International ISBN Agency, which coordinates national agencies in over 150 countries.

An ISBN-13 consists of five parts: the EAN prefix (978 or 979), the registration group (country or language area), the registrant (publisher), the publication element (title), and a check digit. The check digit is calculated using a modulus 10 algorithm with alternating weights of 1 and 3. For ISBN-10, the check digit is computed with weights 10 to 2, and the result can be the letter 'X' for the value 10. The check digit ensures that common errors such as transposition or misreading are detected. The ISBN is not the same as the barcode; the barcode encodes the ISBN along with a price supplement.

The ISBN is assigned by national ISBN agencies, which are coordinated by the International ISBN Agency in London. Publishers apply for blocks of ISBNs, and each distinct format (hardcover, paperback, ebook) requires a separate ISBN. Libraries and booksellers use the ISBN for cataloging and ordering; it is also used in the supply chain for royalty calculations and sales tracking. The ISBN is not a copyright or legal deposit number, and it does not protect intellectual property. Since 2007, the ISBN-13 is used in the global book trade, and the older ISBN-10 is still recognized in some databases.

One lesser-known fact is that the ISBN is not required for all books; self-published authors can purchase them, but some small presses use alternative identifiers. The ISBN is also used for non-book products such as educational software and some digital media, though the scope is limited. The registration group '979' was introduced to expand capacity, and some countries have multiple group numbers. The ISBN is not the same as the ISSN, which identifies periodicals. The check digit algorithm can detect all single-digit errors and most transposition errors, but not all. The ISBN is also used in the ONIX metadata standard for book data exchange.

ISBN-10

The original 10-digit ISBN format used until 2007.

ISBN-13

The current 13-digit ISBN format, introduced in 2007.

Check digit

The final digit of an ISBN, calculated to validate the number.

EAN-13

The barcode standard that encodes the ISBN-13.

Registration group

The part of the ISBN that identifies the country or language area.