November 28, 2021

WorldCat is a bibliographic catalog. It records the collections of nearly 20,000 libraries which, in over 123 countries, participate in the library cooperation of the Online Computer Library Center (OCLC). WorldCat is collectively built and maintained by participating libraries.


The catalog was created by Fred Kilgour in 1967 and became operational in 1971. It is the largest international bibliographic database. OCLC provides WorldCat freely to libraries, but the catalog is the basis for other paid services, such as resource sharing and full library management. In 2003 OCLC initiated the "Open WorldCat" pilot program, making abbreviated records from a section of Worldcat available to partner websites and book retailers to increase their access to the collections of participating libraries. Since 2006 it has been possible to search freely on WorldCat through an internal search engine proposed by its website. In 2007, WorldCat Identities began providing information about the authors and people associated with the published books (for example, those who have written forewords, afterwords and contributions). As of May 2019, WorldCat contained over 450 million bibliographic records in 484 languages, representing over 2.8 billion physical and digital library assets, while the human dataset comprised over 100 million names.


WorldCat operates on a mixed model of real-time updating and batch processing. All the libraries that upload their records to WorldCat carry out updates at predefined intervals with OCLC, while all the libraries (about 25,000) that catalog online enrich the catalog in real time. WorldCat can therefore show that a certain document is present in the library catalog, but not if it is on loan at that moment, or is available. To overcome this problem, there is the possibility for libraries to add direct links to their catalog, in order to allow users to check the circulation status of the document.



Wendy M. Grossman, Why you can't find a library book in your search engine: Finding a book at your local library should just involve a simple web search; but thanks to a US cataloging site, that is far from the case, in The Guardian, January 21, 2009.

Other projects

Wikimedia Commons contains images or other files on WorldCat

External links

(EN, CS, DE, ES, FR, IT, NL, PT, TH, KO, JA, ZH) Official site, on OCLC - "Web scale" discovery and delivery of library resources, at WorldCat Identities, at

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