WorldCat is a union catalog that itemizes the collections of tens of thousands of institutions (mostly libraries), in many countries, that are current or past members of the OCLC global cooperative.[3] It is operated by OCLC, Inc.[4] Many of the OCLC member libraries collectively maintain WorldCat's database, the world's largest bibliographic database.[5] The database includes other information sources in addition to member library collections.[6] 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.

WorldCat homepage as of June 2019
Type of site
Network of library content and services
Available in13 languages[1]
List of languages
  • Chinese (Simplified)
  • Chinese (Traditional)
  • Czech
  • Dutch
  • English
  • French
  • German
  • Italian
  • Korean
  • Japanese
  • Portuguese
  • Spanish
  • Thai
  • Urdu
RegistrationOptional, but some features require registration (such as writing reviews and making lists or bibliographies)
LaunchedJanuary 21, 1998 (1998-01-21) (date of registry of the new domain name; the database already existed since 1971)[2]
Current statusOnline
Content license
Copyright policy
OCLC number756372754

As of December 2021, WorldCat contained over 540 million bibliographic records in 483 languages, representing over 3 billion physical and digital library assets,[4] and the WorldCat persons dataset (mined from WorldCat) included over 100 million people.[7]


OCLC was founded in 1967 under the leadership of Fred Kilgour.[8] That same year, OCLC began to develop the union catalog technology that would later evolve into WorldCat; the first catalog records were added in 1971.[8][9]

In 2003, OCLC began the "Open WorldCat" pilot program, making abbreviated records from a subset of WorldCat available to partner web sites and booksellers, to increase the accessibility of its subscribing member libraries' collections.[10][11]

In October 2005, the OCLC technical staff began a wiki project, WikiD, allowing readers to add commentary and structured-field information associated with any WorldCat record.[12] WikiD was later phased out, although WorldCat later incorporated user-generated content in other ways.[13][14]

In 2006, it became possible for anyone to search WorldCat directly at its open website,[15] not only through the subscription FirstSearch interface where it had been available on the web to subscribing libraries for more than a decade before.[16] Options for more sophisticated searches of WorldCat have remained available through the FirstSearch interface.[15]

In 2007, WorldCat Identities began providing pages for 20 million "identities", which are metadata about names—predominantly authors and persons who are the subjects of published titles.[17]

In 2017, OCLC's WorldCat Search API was integrated into the cite tool of Wikipedia's VisualEditor, allowing Wikipedia editors to cite sources from WorldCat easily.[18][19]

Beginning in 2017, OCLC and the Internet Archive have collaborated to make the Internet Archive's records of digitized books available in WorldCat.[20]

In August 2022, OCLC launched a "redesigned and reimagined" website with the stated goal "to offer greater accessibility to the collections".[21] The website now requires the use of JavaScript and is therefore no longer accessible for users of older web browsers or those that have JavaScript disabled for security reasons. The update also removed users' book reviews and replaced them with reviews from Amazon subsidiary GoodReads.[22]

System architecture

Local catalogs of many OCLC member libraries are intermittently synchronized with the WorldCat database.[23] WorldCat allows participating institutions to add direct links from WorldCat to their own local catalog entries for particular items, which enables the user to click through to the local catalog to quickly determine an item's real-time status (for example, whether or not it is checked out).[24]

In a small percentage of libraries,[25] the local catalog is also run by OCLC using an integrated library system called WorldCat Discovery and WorldShare Management Services.[26]

Library contributions to WorldCat are made via the Connexion computer program,[27] which was introduced in 2001; its predecessor, OCLC Passport, was phased out in May 2005.[28] Cataloging librarians may also use the WorldShare Record Manager[29] or WorldCat Metadata API[30] for similar purposes.[31]

See also


  1. "Search for library items". WorldCat. OCLC. Retrieved March 29, 2017.
  2. 1998 is the date of registry of the domain; see: " WHOIS, DNS, & Domain Info – DomainTools". WHOIS. Retrieved January 21, 2017. However, the union catalog that became WorldCat was started three decades earlier, and it was already available on the web to subscriber libraries at several years before was a registered domain name; see: " WHOIS, DNS, & Domain Info – DomainTools". WHOIS. Retrieved June 26, 2019.
  3. The 2012–2013 OCLC Annual Report noted that the number of "participating libraries (includes active and inactive symbols)" was 78,985: 2012–2013 OCLC Annual Report (Report). p. 5. OCLC 1226313226. Retrieved March 10, 2022.
  4. "Inside WorldCat". OCLC. Retrieved June 19, 2021.
  5. Oswald, Godfrey (2017). "Largest unified international library catalog". Library world records (3rd ed.). Jefferson, NC: McFarland & Company. p. 291. ISBN 9781476667775. OCLC 959650095.
  6. "Content available through WorldCat Discovery" (XLS). OCLC. Retrieved September 22, 2020.
  7. "Data strategy [WorldCat]". Archived from the original on March 27, 2019. Retrieved February 11, 2018.
  8. Margalit Fox (August 2, 2006). "Frederick G. Kilgour, Innovative Librarian, Dies at 92". The New York Times. Retrieved December 22, 2009. Frederick G. Kilgour, a distinguished librarian who nearly 40 years ago transformed a consortium of Ohio libraries into what is now the largest library cooperative in the world, making the catalogs of thousands of libraries around the globe instantly accessible to far-flung patrons, died on Monday in Chapel Hill, N.C. He was 92.
  9. "A brief history of WorldCat". February 10, 2015. Retrieved February 13, 2014.
  10. O'Neill, Nancy (November–December 2004). "Open WorldCat Pilot: A User's Perspective". Searcher. 12 (10): 54–60. ISSN 1070-4795. OCLC 201889986.
  11. Quint, Barbara (October 27, 2003). "OCLC project opens WorldCat records to Google". Information Today. Retrieved June 26, 2019.
  12. "WikiD". OCLC. Retrieved March 5, 2015.
  13. Storey, Tom (September 2007). "A WorldCat community: using to build a social network of the world's library users" (PDF). NextSpace. OCLC (7): 16–17. ISSN 1559-0011. Retrieved June 26, 2019. Online ratings, tags, reviews, recommendations, lists, rankings, personal profiles—the social media revolution is here. It seems the world has exploded with Web 2.0, social networking tools and sites.
  14. Bertot, John Carlo; Berube, Katy; Devereaux, Peter; Dhakal, Kerry; Powers, Stephen; Ray, Jennie (April 2012). "Assessing the usability of WorldCat Local: findings and considerations". The Library Quarterly. 82 (2): 207–221. doi:10.1086/664588. JSTOR 10.1086/664588. S2CID 61287720. Breeding [2] also makes the following observations about the benefits of the search system: the presence of a more visually appealing interface; the grouping of related material; faceted navigation; and the capability for user-generated content (e.g., reviews). Eden [3] also refers to the advantages of user-generated content possible in WCL...
  15. Hane, Paula J. (July 17, 2006). "OCLC to open WorldCat searching to the world". Information Today. Retrieved June 26, 2019.
  16. Prucha, Francis Paul (1994). "National online library catalogs". Handbook for research in American history: a guide to bibliographies and other reference works (2nd ed.). Lincoln: University of Nebraska Press. pp. 25–27. ISBN 0803237014. OCLC 28018047. Online Computer Library Center has developed two new programs. One is called EPIC, a new command-driven full online service with sophisticated searching features, including subject searches, intended for librarians and other experienced users. The other, designed for end-users, is FirstSearch, which contains the database materials found in EPIC or subsets of them but has a menu interface that nonspecialists find easy to use. Both EPIC and FirstSearch make available the full OCLC Online Union Catalog (called WorldCat in FirstSearch), but they also function as online database services, offering their users a wide array of other databases.
  17. Hickey, Thomas B. (April 15, 2007). "WorldCat Identities: Another View of the Catalog" (PDF). NextSpace. OCLC (6): 18–19. ISSN 1559-0011. Retrieved January 18, 2016.
  18. "OCLC and Wikipedia Library link citations to millions of library materials, expanding access to quality sources". OCLC. May 11, 2017. Archived from the original on December 9, 2017. Retrieved April 25, 2020.
  19. Orlowitz, Jake (May 11, 2017). "You can now add automatically generated citations to millions of books on Wikipedia". Wikimedia Foundation. Retrieved April 25, 2020.
  20. Michalko, Jim (October 12, 2017). "Syncing Catalogs with thousands of Libraries in 120 Countries through OCLC". Internet Archive. Retrieved July 18, 2020.
  21. Gary Price (August 24, 2022). "OCLC Officially Announces the Launch of a 'Redesigned and Reimagined'". Retrieved August 29, 2022.
  22. "Frequently Asked Questions". WorldCat. Retrieved August 29, 2022.
  23. "About data sync collections – OCLC Support". OCLC. April 14, 2017. Retrieved June 18, 2021.
  24. "What is WorldCat?". Retrieved February 13, 2015.
  25. Schonfeld, Roger C. (December 5, 2019). "What are the larger implications of Ex Libris buying Innovative?". Retrieved April 25, 2020. OCLC's WorldShare cloud system has yet to achieve critical mass, amounting to 10% of the academic market (but only 4% of ARL), and OCLC's entire public library business represents just 10% of the public library market. For another source of statistics on library system market share, see: "Library Technology Guides: Marketshare Report".
  26. Breeding, Marshall (March 2014). "OCLC announces WorldCat Discovery service". Smart Libraries Newsletter. American Library Association. 34 (3): 6–7. ISSN 1541-8820.
  27. "Connexion – Features". OCLC. Retrieved June 18, 2021.
  28. Dean, Becky (March 3, 2005). "OCLC Authorities migration timeline". (Mailing list). Retrieved June 26, 2019.
  29. "WorldShare Record Manager: Record-at-a-time cataloging service". OCLC. April 2, 2021. Retrieved June 18, 2021.
  30. "WorldCat Metadata API | OCLC Developer Network". OCLC. Retrieved June 18, 2021.
  31. "OCLC cataloging application comparison". OCLC. Retrieved June 18, 2021.

Further reading

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