OCLC Opens up WorldCat through APIs

By Marshall Breeding |

The following article originally appeared in the February 2010 issue of Smart Libraries Newsletter. You can purchase that issue, which contains more of Marshall Breeding's expert analysis of the library automation industry, at http://bit.ly/9Cosm1.

In a move that opens the massive WorldCat database to external developers, OCLC has released a limited set of application programming interfaces (APIs) to programmers outside of its direct membership.  OCLC has offered a more robust API to affiliated organizations for more than a year.  Releasing an API to external, unaffiliated developers, may open up new opportunities that enable library-created bibliographic data to be used in new types of applications. 

Dubbed the WorldCat Basic API, a limited number of Web services have been exposed for non-commercial use.   OCLC also offers the WorldCat Search API, which provides programmatic access to complete bibliographic records.  OCLC limits access to the full WorldCat Search API to qualified institutions.  

WorldCat Search API – Full programmatic access to WorldCat.org

The WorldCat Search API provides a powerful set of services for programmatically searching and retrieving data from WorldCat.  OCLC initially released this API in August 2008.  This API essentially allows external developers to create applications that make use of the 150 million-item WorldCat bibliographic database. 

The WorldCat Search API involves requests submitted through the OpenSearch protocol or SRU CQL syntax.  OpenSearch finds broad use for all types of information environments.  SRU, loosely based on the Z39.50 protocol and implemented as a Web service, is used primarily in library-specific applications.  In response to SRU search requests, the API responds with records from WorldCat, formatted in MARC XML or in Dublin Core.  Requests sent through OpenSearch results can also be returned as RSS or Atom feeds.  Records in responses can also be delivered in one of several supported bibliographic citation formats, including APA, Chicago Manual of Style, Harvard, MLA, or Turabian. 

The WorldCat Search API makes it possible to embed information from WorldCat in third-party applications.  Such applications could display lists of resources found in WorldCat, present bibliographic details for any given resource, and show an item’s availability in libraries. The OCLC Web Services Application Gallery shows other examples of how the WorldCat Search API has been used (see: http://www.oclc.org/worldcatapi/applicationgallery/). OCLC provides complete documentation for the API that provides the information required by programmers to send requests and to receive and interpret response data. 

Individuals affiliated with qualifying institutions can use the WorldCat Search API without cost.  These institutions include libraries that contribute their holdings to WorldCat and that make their holdings visible on WorldCat.org. Libraries without that level of involvement with OCLC may use the more limited WorldCat Basic API.  OCLC encourages commercial use of WorldCat API, although such use must be negotiated in advance.

WorldCat Basic API

In December 2009, OCLC released a limited version of the WorldCat Search API to all interested developers for non-commercial use, even if they are not directly affiliated with a library or OCLC.   This version of the API only supports queries submitted through OpenSearch and returns more limited results.  While the full version of the API can provide a complete record from WorldCat in MARC XML, the WorldCat Basic API provides a subset of the bibliographic information in RSS or Atom, and may include citation formats.  The specific bibliographic fields available in responses include authors, titles, ISBN, and OCLC Record Number.  Results also include a link to the full record in WorldCat.org, where users can find the item in a nearby library, initiate an interlibrary loan request, read reviews and ratings, add items to lists and more. 

In order to use either WorldCat API, it is necessary to register and obtain a unique identifier used as a developer key.  Other API’s, such as those made available by Amazon.com and Google, also require registration and use developer keys. The Basic API key is available immediately; the Search API key requires verification of eligibility.



WorldCat Search API

WorldCat Basic API


SRU (Search/Retrieve URL)




Dublin Core


Bibliographic Citation Formats