“ISBN” stands for “International Standard Book Number”. An ISBN is a number, not a bar code. One agency per country is designated to assign ISBNs for the publishers and self-publishers located in that country. The U.S. ISBN Agency cannot assign ISBNs to publishers and self-publishers located outside the United States and its territories.
The ISBN identifies the title or other book-like product (such as an audiobook) to which it is assigned, but also the publisher to be contacted for ordering purposes. If an ISBN is obtained from a company other than the official ISBN Agency, that ISBN will not identify the publisher of the title accurately. This can have implications for doing business in the publishing industry supply chain.
ISBNs are assigned to publishers and self-publishers as follows: 1, 10, 100, 1,000, 10,000 or 100,000 numbers.
When participating in the ISBN standard, publishers and self-publishers are required to report all information about titles to which they have assigned ISBNs. For more than thirty years, ISBNs were 10 digits long. On January 1, 2007 the ISBN system switched to a 13-digit format. Now all ISBNs are 13-digits long. If you were assigned 10-digit ISBNs, you can convert them to the 13-digit format at the converter found at this website. A 10-digit ISBN cannot be converted to 13-digits merely by placing three digits in front of the 10-digit number. There is an algorithm that frequently results in a change of the last digit of the ISBN.