What is an ISBN?

An ISBN is an International Standard Book Number. ISBNs were 10 digits in length up to the end of December 2006, but since 1 January 2007 they now always consist of 13 digits. ISBNs are calculated using a specific mathematical formula and include a check digit to validate the number.

Each ISBN consists of 5 elements with each section being separated by spaces or hyphens. Three of the five elements may be of varying length:

  • Prefix element – currently this can only be either 978 or 979. It is always 3 digits in length

  • Registration group element – this identifies the particular country, geographical region, or language area participating in the ISBN system. This element may be between 1 and 5 digits in length

  • Registrant element - this identifies the particular publisher or imprint. This may be up to 7 digits in length
  • Publication element – this identifies the particular edition and format of a specific title. This may be up to 6 digits in length

  • Check digit – this is always the final single digit that mathematically validates the rest of the number. It is calculated using a Modulus 10 system with alternate weights of 1 and 3.

What is an ISBN used for?

An ISBN is essentially a product identifier used by publishers, booksellers, libraries, internet retailers and other supply chain participants for ordering, listing, sales records and stock control purposes. The ISBN identifies the registrant as well as the specific title, edition and format.

What does an ISBN identify?

ISBNs are assigned to text-based monographic publications (i.e. one-off publications rather than journals, newspapers, or other types of serials).

Any book made publicly available, whether for sale or on a gratis basis, can be identified by ISBN.

In addition, individual sections (such as chapters) of books or issues or articles from journals, periodicals or serials that are made available separately may also use the ISBN as an identifier.

With regard to the various media available, it is of no importance in what form the content is documented and distributed; however, each different product form (e.g. paperback, EPUB, .pdf) should be identified separately.

You can find examples of types of qualifying products and more information about the scope of the ISBN here.

ISBNs, the law and copyright

The ISBN is an identifier and does not convey any form of legal or copyright protection. However, in some countries the use of ISBN to identify publications has been made into a legal requirement.

Who should apply for ISBN? 

It is always the publisher of the book who should apply for the ISBN. For the purposes of ISBN, the publisher is the group, organisation, company or individual who is responsible for initiating the production of a publication. Normally, it is also the person or body who bears the cost and financial risk in making a product available. It is not normally the printer, but it can be the author of the book if the author has chosen to publish their book themselves. 

In a number of countries there is detailed legislation regarding publishing so contact your national ISBN agency in good time for advice.