WorldCat is a union catalog that itemizes the collections of 15,637 libraries in 107 countries that participate in the OCLC global cooperative. It is operated by OCLC, Inc. The subscribing member libraries collectively maintain WorldCat's database, the world's largest bibliographic database. The database includes other information sources in addition to member library collections. 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.