ISBN10

ISBN-10 is a ten-character identifier used for books and related products. It was introduced in 1970 to provide a consistent, internationally recognized way to identify editions and publishers. An ISBN-10 consists of nine digits plus a check digit; the check digit can be 0–9 or the letter X, which represents the value 10. Hyphens are sometimes included to separate group, publisher, and title elements, but they are not part of the identifier itself.

The first nine characters encode a combination of group, publisher, and item numbers, while the tenth character is the check digit. The system is designed so that each edition of a book has a unique ISBN-10. The check digit is derived from the preceding digits to ensure accuracy in transcription and data entry, aiding error detection in catalogs and barcodes.

To compute the check digit, multiply the first nine digits by weights 10 down to 2, sum the results, take the remainder when divided by 11, and subtract that remainder from 11. The resulting value is the check digit; if the result is 10, the check digit is written as X; if the result is 11, the check digit is 0. This method allows most single-character errors or transpositions to be detected.

ISBN-10 was the standard for many years, but a transition to ISBN-13 began in the early 2000s to align with the global EAN barcode system. From 2007 onward, new titles commonly used ISBN-13, and many catalogs store both forms for compatibility. Conversion from ISBN-10 to ISBN-13 involves prefixing the first nine digits with 978, then recalculating the check digit using the ISBN-13 algorithm.

Today, ISBN-10 remains in use for older titles and archival databases, where it continues to identify a specific edition or format independent of its ISBN-13 counterpart.