The International Standard Book Number on a book is located on its bar code, which is typically located on the back side of the book or on the title page. It can also be located on a book's copyright page.
The ISBN is usually labeled and is a 10- or 13-digit code specific to the book's publisher, title and edition. A book published after 2007 has a 13-digit code, and a book published before the end of December 2006 has a 10-digit code.
To search for an ISBN online, enter the title of the book or its author in an ISBN search website to look up the book.