Why are there two ISBN numbers to a book? Which do you use when listing a book on sale?

Just curious.|||On January 1, 2007, the global book industry began the transition to 13-digit ISBNs, slowly phasing out the use of 10-digit numbers. The change to 13 digits was needed in order to expand the numbering capacity of the ISBN system and alleviate numbering shortages in certain parts of the world.





However, if they choose, some publishers may display BOTH the ISBN-10 and the ISBN-13 numbers on their books, during the transition to ISBN-13. While it is preferable to print only ISBN-13 numbers, some publishers will continue dual numbering/printing until the marketplace fully completes the transition to ISBN-13--hopefully sometime in 2008. That's why we still see some books with two ISBN's.





If you had to choose a single number-format to list for promotional reasons, I would say choose the ISBN-13, because that's the number-format everyone is moving to. However, listing both numbers wouldn't hurt, until the transition is complete.|||The number of digits used in ISBNs increased recently to provide more information. Some older books use the older version but also have a new number. Both will work.|||Both will work, but if you are listing a lot of books stick to one set or the other.|||A book can have two or more ISBNs. Most likely it's because the publisher published the book in different countries. Each country has different ISBN blocks, hence the multiple ISBNs. Sometimes publishers also put two ISBNs to indicate the paperback and hardcover version.





For a book list, I think you can just simply take any ISBN that's printed on the book.