Inside WorldCat
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Inside WorldCat
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Inside WorldCat
WorldCat consists of three components: a bibliographic catalog, a knowledge base, and a registry for library information.
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 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
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“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
WorldCat growth
Number of bibliographic records
(as of February 2021)
Number of holdings
(as of February 2021)
Bibliographic records
Local holdings
Local bibliographic data
(February 2020–February 2021)
WorldCat gets more than one new record
every second
Members fill an ILL request
every second
Watch WorldCat grow.
Watch in real time as librarians and information service professionals from all over the world contribute records to WorldCat.
Language composition of WorldCat items
(as of January 2021)
Number of languages
(as of January 2021)
More language statistics
Scripts represented in WorldCat
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.
The knowledge base also includes free and open-access materials that users can find and get alongside their library’s materials. As of February 2021, the knowledge base provides access to more than 52,330,663 records and 17,851 content collections from 731 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
Sharing holdings to improve discovery
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“Drastically improved discovery…”
“We have title-level OCLC cataloging for most of our subscribed databases, which is amazing. ...It has drastically improved discovery.”
Maurine McCourry
Technical Services Librarian
Hillsdale College
Hillsdale, Michigan, United States
Read Hillsdale’s story
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.
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