ISBN10s

ISBN-10 refers to the ten-digit International Standard Book Number used to uniquely identify books and related products. It was introduced as part of the international ISBN system and remained the standard identifier for many titles until the widespread adoption of ISBN-13 starting in 2007. Although new publications primarily use ISBN-13, ISBN-10s still appear in many catalogs and on older books.

Structure and format: An ISBN-10 consists of ten characters. The first nine are digits, and the tenth is a check digit that can be a digit 0–9 or the letter X, which represents the value 10. The check digit is determined so that the weighted sum of all ten digits (with weights 1 through 10 for positions 1 to 10) is a multiple of 11. Because of this calculation, X can appear only as the final character.

Hyphenation and grouping: ISBN-10s are often written with hyphens to indicate group, publisher, title, and check digit components, but the exact grouping varies by country and publisher.

Conversion to ISBN-13: To convert an ISBN-10 to ISBN-13, the first nine digits of the ISBN-10 are prefixed with 978, producing a 12-digit number, and a new check digit is calculated using the ISBN-13 algorithm (modulo 10 with alternating weights of 1 and 3). The resulting 13-digit code is used for most modern registrations and catalogs.

Usage and limitations: ISBN-10s remained in use for identification and inventory in libraries, bookstores, and publishers, especially for older or legacy titles. They are not sufficient for new publications after the transition to ISBN-13, which provides a larger namespace and standardized prefixing.