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Five-color WorldCat emblem, with WorldCat in black letters and OCLC in smaller grey letters
WorldCat homepage, 29 March 2017
Type of site
Network of library content and services
Available in13 languages[1]
Template:Begin hidden
  • Chinese (Simplified)
  • Chinese (Traditional)
  • Czech
  • Dutch
  • English
  • French
  • German
  • Italian
  • Korean
  • Japanese
  • Portuguese
  • Spanish
  • Thai
  • Urdu
Template:End hidden
OwnerOnline Computer Library Center
Alexa rankIncrease 3,446 (Global 03/2017)
RegistrationOptional, but some features require registration (such as writing reviews and making lists or bibliographies)
LaunchedJanuary 21, 1998; 25 years ago (1998-01-21)[2]
Current statusOnline
Content license
Copyright policy
IP address132.174.11.84
OCLC number756372754

WorldCat is a union catalog that itemizes the collections of 72,000 libraries in 170 countries and territories[3] that participate in the Online Computer Library Center (OCLC) global cooperative. It is operated by OCLC Online Computer Library Center, Inc.[4] The subscribing member libraries collectively maintain WorldCat's database, the world's largest bibliographic database. 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).


OCLC was founded in 1967 under the leadership of Fred Kilgour.[5] 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.[5][6]

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. In 2006, it became possible to search WorldCat directly at its website. In 2007, WorldCat Identities began providing pages for 20 million "identities", predominantly authors and persons who are the subjects of published titles.[7]

As of December 2017, WorldCat contains over 400 million bibliographic records in 491 languages, representing over 2.6 billion physical and digital library assets,[3] and the WorldCat persons dataset (mined from WorldCat) includes over 100 million people.[8]


WorldCat operates on a batch processing model rather than a real-time model. That is, WorldCat records are synchronized at intermittent intervals with the underlying library catalogs instead of real-time or every day. Consequently:

  • WorldCat shows that a particular item is owned by a particular library but does not provide that library's call number.
  • WorldCat does not indicate whether or not an item is currently borrowed, lost, undergoing restoration or repair, or moved to storage not directly accessible to patrons (thereby forcing interested patrons to submit a retrieval request and wait).
  • Furthermore, WorldCat does not show whether or not a library owns multiple copies of a particular title.

As an alternative, WorldCat allows participating institutions to add direct links from WorldCat to their own catalog entries for a particular item, which enables the user to determine its real-time status.[4] However, this still requires users to open multiple Web pages, each pointing to a different OPAC with its own distinctive user interface design (which places item status in a different portion of the Web browser display), until they can locate a catalog entry that shows the item is currently available at a particular library.

See also


  1. "Search for library items". Online Computer Library Center. 
  2. " WHOIS, DNS, & Domain Info - DomainTools". WHOIS. Retrieved 2017-01-21. 
  3. 3.0 3.1 "Inside WorldCat". Online Computer Library Center. Retrieved February 11, 2018. 
  4. 4.0 4.1 "What is WorldCat?". Retrieved 13 February 2015. 
  5. 5.0 5.1 Margalit Fox (August 2, 2006). "Frederick G. Kilgour, Innovative Librarian, Dies at 92". The New York Times. Retrieved 2009-12-22. "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." 
  6. "A brief history of WorldCat". February 10, 2015. Retrieved February 13, 2014. 
  7. Hickey, Thomas B. (15 April 2007). "WorldCat Identities: Another View of the Catalog". NextSpace (OCLC) (6): 18–19. ISSN 1559-0011. Retrieved 18 January 2016. 
  8. "Data strategy [WorldCat"]. Retrieved 11 February 2018. 

Further reading

  • Blackman, Cathy; Moore, Erica Rae; Seikel, Michele; Smith, Mandi (July 2014). "WorldCat and SkyRiver: a comparison of record quantity and fullness". Library Resources & Technical Services 58 (3): 178–186. doi:10.5860/lrts.58n3.178. 
  • Breeding, Marshall (May 2015). "Library services platforms: a maturing genre of products". Library Technology Reports 51 (4): 1–38. doi:10.5860/ltr.51n4. 
  • Matthews, Joseph R. (July 2016). "An environmental scan of OCLC alternatives: a management perspective". Public Library Quarterly 35 (3): 175–187. doi:10.1080/01616846.2016.1210440. 
  • McKenzie, Elizabeth (January 2012). OCLC changes its rules for use of records in WorldCat: library community pushback through blogs and cultures of resistance (Technical report). Boston: Suffolk University Law School. Research paper 12-06.
  • What the OCLC online union catalog means to me: a collection of essays. Dublin, Ohio: OCLC. 1997. ISBN 1556532237. OCLC 37492023. 
  • Wilson, Kristen (August 2016). "The knowledge base at the center of the universe". Library Technology Reports 52 (6): 1–35. doi:10.5860/ltr.52n6. 

External links