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Inside WorldCat

WorldCat consists of three components: a bibliographic catalog, a knowledge base, and a registry for library information.

icon for the WorldCat bibliographic catalog

The worldwide catalog of library resources

The WorldCat bibliographic catalog includes everything that’s available to users in the library. Beyond books and print journals, the catalog of physical materials includes DVDs, historic photos, video games, musical scores, newspapers, webpages and many other standard items. It also includes unique items, such as 2,700-year-old jewelry, 18th century soup bowls and Soviet civilian medals.

In 1971, librarians in Alden Library at Ohio University added the first bibliographic records to what was then known as the OCLC Online Union Catalog. Within eight years, the catalog already included more than five million records. Now known as WorldCat, the catalog today includes millions of records and billions of holdings.

As the WorldCat bibliographic catalog continues to grow in quantity, efforts to improve the quality also increase. Professional catalogers all over the world consistently improve WorldCat records to make them as complete and useful as possible. This cooperative resource simplifies cataloging, maintenance, interlibrary loan and discovery tasks for libraries worldwide.

Learn more about WorldCat data quality

How WorldCat evolves

WorldCat has continued to keep up with the way modern library users prefer to consume media. From print books to streaming video and beyond, you can find it in WorldCat. Here are a just a few of the many formats that have been added to WorldCat over the years.

WorldCat launches with:





Musical scores





Audio cassettes

Sound recordings



Computer files


Floppy discs


Audio CDs






Streaming video


Blu-ray discs

Italicized years are approximate

Celebrating 45 years of WorldCat

Scott Seaman [photo]

“The world’s knowledge…”

“Modern scholarship would not have been possible without the creation of WorldCat. … To have the world’s knowledge cataloged and made available has just been an extraordinary miracle. And to have been the first contributor is almost unthinkable. It’s such an honor.”

Scott Seaman
Dean of Libraries, Ohio University
Athens, Ohio, United States

Vital statistics

Number of bibliographic records

380,812,918 (as of September 2016)

Number of holdings

2,466,078,986 (as of September 2016)

WorldCat gets a new record

Every second

Members fill an ILL request

Every 2 seconds

Percentage of non-English records

62% (as of July 2016)

Number of languages and dialects represented

491 (as of July 2016)

Watch WorldCat grow.

Watch in real time as librarians and information service professionals from all over the world contribute records to WorldCat.

WorldCat growth from August 2015 to August 2016


Bibliographic records




Local holdings


Local bibliographic data


icon for the WorldCat knowledge base

A knowledge base to connect users to e-resources

The WorldCat knowledge base connects library users to the electronic content provided by their library. It combines data about a library’s e-resources with linking features that make the collections easier to find, share, manage and use. Like data in the WorldCat bibliographic catalog, knowledge base data are not tied to a particular application, so libraries can streamline electronic content workflows across multiple systems.

The WorldCat knowledge base’s cooperatively maintained collections continue to grow with content from libraries and publishers from around the world. Because OCLC is a non-profit, vendor-neutral cooperative, the WorldCat knowledge base is the only source that includes records from both EBSCO and ProQuest, Gale and Springer, and Wiley and Elsevier, among many other content suppliers.

Logos of some of our partners in the WorldCat knowledge base: ProQuest, EBSCO, Elsevier, Springer, Taylor and Francis, McGraw Hill Education, Wiley, Ingram, Cambridge University Press, Gale Cengage Learning, ebrary, Oxford University Press.

The knowledge base also includes free and open-access materials that users can find and get alongside their library’s materials. As of May 2016, the knowledge base provides access to more than 29 million records and 15,756 content collections from 6,218 providers. Download an Excel spreadsheet that lists all knowledge base collections to see what’s available today.

Download a white paper on e-resource challenges

Collective cataloging in Canada using the WorldCat knowledge base

Marilyn Murphy [photo]

“Discovering more resources…”

“With our electronic holdings in the WorldCat knowledge base, 'View Online’ links take our students from search results to full-text articles. …Students are discovering more resources, and they are making better use of our existing databases. …In the first year, we experienced a 25% increase in the number of downloads of full-text articles from our databases, a 23% increase in e-journal article lending and a 25% increase in book borrowing. Our article borrowing decreased 11% because of the increase in downloads of full text.”

Marilyn Murphy
Director of Library Services
Mount Mercy University
Cedar Rapids, Iowa, United States


icon for the WorldCat registry

A registry of library profiles to increase visibility

The WorldCat registry allows libraries to maintain information about their services and contacts to help information seekers find the library online. When librarians maintain their institution’s location, hours, relationships, services and contact information, the WorldCat registry populates that information on and elsewhere through links on popular websites. Library staff can also share profiles with vendors and consortium members to ensure they always have the most accurate contact information.

Visit the WorldCat registry

Find in a Library links

Services across the internet help people find great books to read. The WorldCat data embedded into those websites through “Find in a Library” links help direct readers to libraries near them that hold the book they want. The WorldCat registry provides the location and other information needed to connect libraries with readers.