[5] OCLC is funded mainly by the fees that libraries pay (around $217.8 million annually in total as of 2021[update]) for the many different services it offers.

[7][8] Kilgour and Ralph H. Parker, who was the head of libraries at the University of Missouri, had proposed the shared cataloging system in a 1965 report as consultants to the Committee of Librarians of the Ohio College Association.

[8] Kilgour and Parker wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library.

[8] They were inspired in part by the earlier Columbia–Harvard–Yale Medical Libraries Computerization Project, an attempt at shared automated printing of catalog cards.

[14] In 2022, membership and governance expanded to include any institution with a subscription to one of many qualifying OCLC products (previously institutions qualified for membership by "contributing intellectual content or participating in global resource or reference sharing"), with the exception of for-profit organizations that are part of OCLC's partner program.

The Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988.

OCLC staff members meet and work regularly with library leaders, information professionals, researchers, entrepreneurs, political leaders, trustees, students and patrons to advocate "advancing research, scholarship, education, community development, information access, and global cooperation".

[39][40] WebJunction, which provides training services to librarians,[41] is a division of OCLC funded by grants from the Bill & Melinda Gates Foundation beginning in 2003.

[42][43] OCLC partnered with search engine providers in 2003 to advocate for libraries and share information across the Internet landscape.

Google, Yahoo!, and Ask.com all collaborated with OCLC to make WorldCat records searchable through those search engines.

[44] Other past advocacy campaigns have focused on sharing the knowledge gained from library and information research.

Such projects have included communities such as the Society of American Archivists, the Open Archives Initiative, the Institute for Museum and Library Services, the International Organization for Standardization, the National Information Standards Organization, the World Wide Web Consortium, the Internet Engineering Task Force, and Internet2.

One of the most successful contributions to this effort was the Dublin Core Metadata Initiative, "an open forum of libraries, archives, museums, technology organizations, and software companies who work together to develop interoperable online metadata standards that support a broad range of purposes and business models.

[45][54] OCLC acquired NetLibrary, a provider of electronic books and textbooks, in 2002 and sold it in 2010 to EBSCO Industries.

In 2013, OCLC acquired the Dutch library automation company HKA[60][61] and its integrated library system Wise,[27] which OCLC calls a "community engagement system" that "combines the power of customer relationship management, marketing, and analytics with ILS functions".

[62] In 2017, OCLC acquired Relais International, a library interlibrary loan service provider based in Ottawa, Canada.