It is the oldest of the three ONIX standards, and is widely implemented in the book trade in North America, Europe and the Asia–Pacific region.
It allows book and ebook publishers to create and manage rich metadata about their products, and to exchange it with their customers (distributors and retailers).
The latest version is 3.0.7, released in October 2019, and the standard continues to evolve to meet new business requirements as they emerge.
[1] The international steering committee announced in January 2012 that support for version 2.1 would be reduced at the end of December 2014.
Releases 2.1 and 3.0 share a set of 'Codelists', or controlled vocabularies, that are extended regularly to allow new types of information to be carried out without having to revise the main specifications.