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The WorldCat difference: connect to and leverage our shared catalog

A unique resource, WorldCat is the world's most comprehensive online library database. The database encompasses hundreds of languages and all formats, including rapidly growing numbers of electronic resources and digital objects.

High hit rates, quality-controlled metadata and the application of FRBR principles to records mean your patrons and staff locate the right resource quickly. WorldCat spreads data about library collections across the Web via strategic partnerships.  

With your holdings in WorldCat:

  • Your library can belong to the WorldCat Resource Sharing network of more than 10,163 libraries that have the ability to provide unmatched customer satisfaction
  • Information seekers link to your catalog through search engines, browser toolbars, the WorldCat.org destination site and more.

WorldCat embodies the best of what is possible through collaboration and is a tribute to the cooperative spirit of libraries and librarians. As a result of efforts by OCLC and the member libraries, WorldCat is much more than a catalog of library metadata. It's a hub around which information discovery, resource sharing, delivery, automation and research as well as collection and library system management occur.

Sources of records in WorldCat

Libraries from around the world use WorldCat records to update and maintain their own catalogs. For many libraries, the majority of records found in a local catalog come from copy cataloging of records originally created by OCLC member institutions. While records come in to WorldCat from a variety of sources, the ongoing work of dedicated OCLC member catalogers still provides the most valuable data used to keep collection information accurate, and make collections shareable, visible and useful to information seekers. This, in turn, significantly reduces the need for original cataloging at a member's library, saving time and freeing up staff for other important work.

The variety of record sources for WorldCat also continues to grow. The diversity of methods for contributing to WorldCat ensures that more types of libraries and other institutions can contribute to the cooperative and make their collections highly visible to a worldwide audience. This, in turn, means more records, less cost and better visibility and resource sharing. Records come into WorldCat from online cataloging and batchloading; from the smallest public libraries to the largest national libraries in the world; from archives, museums and research institutions; from publishers and partners who contribute their metadata or have OCLC catalogers create it; all contributing to a single, comprehensive source for library data.

All titles in WorldCat

335 million records

77.09% OCLC Member Libraries; 17.38% Other National Libraries; 2.18% Vendors and Publishers; 3.34% Library of Congress

Titles published 2009—2014

30 million records

66.32% OCLC Member Libraries; 16.84% Other National Libraries; 2.79% Library of Congress; 14.05% Vendors and Publishers;

*Updated February 2015

Information discovery

WorldCat is the combined global catalog of more than 10,163 libraries around the world. Library users can find materials in any of these libraries on the open web through WorldCat's public website.

Resource sharing

Libraries with holdings information in WorldCat can participate in the resource sharing network, composed of more than 10,163 libraries worldwide. WorldCat's tens of millions of records represent library-owned resources—both physical and digital—that cross all manner of subjects, languages, cultures and uniqueness. Participating libraries fill 95 percent or more of requests, reinforcing the perception that their libraries are "one-stop" providers of essential services.


The global, resource sharing network built around WorldCat provides library users worldwide with bibliographic, abstract and full-text information when and where they need it. OCLC delivery services give libraries an unmatched ability to satisfy their users with more than 2.3 billion holdings—physical and electronic—in WorldCat.

Shared data

To maximize the visibility of libraries—and library collections—and to enrich and inform the information environment in as many ways as possible, the OCLC cooperative shares and reuses WorldCat data with many partners across the information industry. Over the past decade, the range and number of OCLC partnerships have grown significantly—national libraries, content aggregators, content providers, publishers, materials vendors, search engines, online booksellers, to name a few. These alliances advance libraries and bring library services and information to people through avenues that often start outside the library.

OCLC also encourages the use, re-use and sharing of WorldCat data within a cooperative framework by members. Member libraries are sharing their WorldCat data with scholars, library consortia, public agencies, cultural and scholarly institutions and other OCLC and non-OCLC members.


Here are some other ways OCLC members are extending the value they receive from WorldCat.

  • Volunteer librarians and developers are bringing their creativity and practical skills to software solutions through the OCLC Developer Network. Established in 2008, the Developer Network builds machine-to-machine applications (Web Services) for WorldCat search and retrieval, as well as protocols for sharing data and services. To date, 70 developers have built more than 60 applications, which are shared worldwide. These apps are accessed more than 10 million times a month. While members have always been closely involved in development and testing of OCLC services, the Developer Network brings a new dimension to development efforts that benefit all members of the cooperative.
  • OCLC Research prototypes and tests new technologies for using WorldCat data and makes them available to the worldwide library community.
    • WorldCat Identities creates a summary page for some 25 million personal and corporate authors mentioned in WorldCat.
    • WorldCat Genre profiles allow users to browse genre terms for hundreds of titles, authors, subjects, characters, places, and more, ranked by popularity in WorldCat.
    • WorldCat Publisher Pages presents a page each for more than 1,800 publishers in WorldCat from around the world.
    • FictionFinder is a FRBR-based prototype that provides access to over 2.9 million bibliographic records for fiction books, e-books, and audio materials described in WorldCat.
    • Audience Level explores using library holdings data in WorldCat to calculate audience-level indicators for books represented in WorldCat, based on the types of libraries that hold the titles.
    • Metadata Crosswalk transforms metadata from one format to another, such as MARC to MODS (Metadata Objects Description Schema).

Through the OCLC cooperative, the library community has built and maintained a metadata creation and management service that has been remarkably stable and useful for 40 years. Because of the individual efforts of thousands of anonymous catalogers and librarians, WorldCat is born every day with new content to serve scholars, researchers and information seekers.

Find the right cataloging service for your library