International Standard Book Numbers (ISBNs) are due to change from 10 to 13 digits in 2007. Some publishers have already started using the new system. The expansion of self-publishing and ebook publishing means that there is little capacity left in the 10 digit numbering system. Although the 10 digit system theoretically allows one billion different numbers, the actual possibilities are limited because of the way the ISBNs are divided into group identifier, publisher identifier, title identifier and check digit. The new 13 digit ISBN will also make book numbering compatible with the 13 digit European Article Numbering (EAN) system. This is useful so that books can easily be sold from non-traditional outlets, such as supermarkets and shops. Existing 10 digit ISBNs will automatically be converted by having a 3 digit prefix.
