WorldCat is a union catalog that itemizes the collections of tens of thousands of institutions (mostly libraries), in many countries, that are current or past members of the OCLC global cooperative.[3] It is operated by OCLC, Inc.[4] Many of the OCLC member libraries collectively maintain WorldCat's database, the world's largest bibliographic database.[5] The database includes other information sources in addition to member library collections.[6] OCLC makes WorldCat itself available free to libraries, but the catalog is the foundation for other subscription OCLC services (such as resource sharing and collection management). WorldCat is used by librarians for cataloging and research and by the general public.
As of December 2021[update], WorldCat contained over 540 million bibliographic records in 483 languages, representing over 3 billion physical and digital library assets,[4] and the WorldCat persons dataset (mined from WorldCat) included over 100 million people.[7]
^1998 is the date of registry of the WorldCat.org domain; see: "WorldCat.org WHOIS, DNS, & Domain Info – DomainTools". WHOIS. Archived from the original on June 20, 2019. Retrieved January 21, 2017. However, the union catalog that became WorldCat was started three decades earlier, and it was already available on the web to subscriber libraries at OCLC.org several years before WorldCat.org was a registered domain name; see: "OCLC.org WHOIS, DNS, & Domain Info – DomainTools". WHOIS. Archived from the original on June 26, 2019. Retrieved June 26, 2019.
^The 2012–2013 OCLC Annual Report noted that the number of "participating libraries (includes active and inactive symbols)" was 78,985: 2012–2013 OCLC Annual Report (Report). p. 5. OCLC1226313226. Retrieved March 10, 2022.