January 28, 2022

Metadata: More than One Billion (and Counting) OCLC Control Numbers Now in Public Domain

There are now more than 1 billion OCLC Control Numbers and today OCLC formally announced they’re now in the public domain.

First, if you’re unaware of what OCLC Control Numbers here are two simple definitions from OCLC.

The OCLC Control Number is a unique, sequentially assigned number associated with a record in WorldCat. The number is included in a WorldCat record when the record is created. The OCLC Control Number enables successful implementation and use of many OCLC products and services, including WorldCat Local and WorldCat Navigator.

The OCN identifies the record, but is not part of the record itself. It is used in a variety of human and machine-readable processes, both on its own and in subsequent manipulations of catalog data.

Now in the Public Domain

From the OCLC Research “Hanging Together” Blog Post by Jim Michalko:

Recently we recommended that OCLC declare OCLC Control Numbers (OCN) as dedicated to the public domain. We wanted to make it clear to the community of users that they could share and use the number for any purpose and without any restrictions. Making that declaration would be consistent with our application of an open license for our own releases of data for re-use and would end the needless elimination of the number from bibliographic datasets that are at the foundation of the library and community interactions.


The declaration now appears on the WCRR web page and from the page describing OCNs and their use.

We think this is important to do to counter act some practices based on misunderstandings that emerged from concerns about OCLC having an overly restrictive record use and re-use policy.

In the remainder of Michalko’s blog post, he discusses the misunderstandings and provides six basic examples of how OCNs are used by librarians and publishers.

Learn More About OCLC Control Numbers

From the Licensing Info Page

Open Data Commons Attribution License (ODC-BY), which means you should: attribute your use of this database to us and OCLC, and; review the OCLC community norms for how we would like our institutions to be treated.

About Gary Price

Gary Price (gprice@mediasourceinc.com) is a librarian, writer, consultant, and frequent conference speaker based in the Washington D.C. metro area. Before launching INFOdocket, Price and Shirl Kennedy were the founders and senior editors at ResourceShelf and DocuTicker for 10 years. From 2006-2009 he was Director of Online Information Services at Ask.com, and is currently a contributing editor at Search Engine Land.