The ISBN is the world’s key identifier for books of all kinds and in all sorts of formats. Introduced more than 40 years ago, it quickly spread to all the major publishing centres of the world. Today it has been adopted in over 200 countries and territories and there are more than 150 national ISBN Agencies that allocate ISBNs to publishers.

Every day, readers, librarians, bookshops, publishers, wholesalers, bibliographic services and internet retailers use ISBN to find and order books, maintain stock control, monitor and track sales, manage royalty payments as well as to compile printed and online catalogues and databases. In short ISBN is used in all aspects of production, publication, discovery, assessment and purchase.

All ISBNs comprise 13 digits and all follow the same structure:

• Prefix element (three digits – currently either 978 or in a few cases 979)
• Registration group element (variable length - between one and five digits)
• Registrant element (variable length – between one and seven digits)
• Publication element (variable length – between one and six digits)
• Check digit (one digit – algorithmically validates the rest of the number)
   

Each title and each different format, language or edition in which that title is available needs to be identified by a separate ISBN.

To apply for ISBN publishers should contact the national ISBN agency in the country where they are based – irrespective of the language of their book or where it will be printed or sold.

More information about the ISBN is available here