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xISBN (Web service)

Use this Web service to retrieve a list of International Standard Book Numbers (ISBNs) associated with a submitted ISBN, based on WorldCat information. Free and subscription versions are available.

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The xISBN Web service supplies ISBNs and other information associated with an individual intellectual work that is represented in WorldCat. Submit an ISBN to this service, and it returns a list of related ISBNs and selected metadata.

Ideal for Web-enabled search applications—such as library catalogs and online booksellers—and based on associations made in the WorldCat database, xISBN enables an end user to link to information about other versions of a source work.

How xISBN works

ISBNs are related to each other in WorldCat using an algorithm developed by OCLC Research. The algorithm restructures WorldCat bibliographic records to conform to the FRBR conceptual model for information objects. For instance, rather than requiring an end user to traverse multiple records that represent many different manifestations of a book—including printings, hardback or paperback editions or even filmed versions—"FRBRized" WorldCat information allows that user to review a core record that lists all manifestations.

The xISBN Web service queries database tables in WorldCat created by the FRBR algorithm.

Using the xISBN Web service

To use the service, you submit a single, known ISBN value embedded in a URL to the xISBN server, and the server returns a list of associated ISBNs and relevant metadata. The ISBNs are sorted by the number of times each represented item is held by a WorldCat library, highest to lowest. Therefore, the first returned ISBN represents the most-held item in WorldCat among all associated items.

You may receive associated ISBNs in either XML, XHTML, Python, Json or Ruby format. The xISBN server supports REST-based requests as well as the OpenURL and unAPI protocols.

The ISBNs returned from the service can in turn be re-used in an "or" query to a bibliographic database to improve the chances of an end user finding all instances of the work in a given database. For example, a user finding an item of interest at an online bookseller could conveniently query a local library's online catalog to find out if any editions or printings of the item are held by the library.


The xISBN Web service is free for non-commercial use when usage does not exceed 500 requests per day. Free usage is governed by the WorldCat Affiliate Terms and Conditions. See the xISBN API for instructions.

The service is also available on a subscription basis for non-commercial and commercial use for usage that meets or exceeds 500 requests per day. Subscription-based use is governed by the WorldCat Affiliate Terms and Conditions for Subscription Access and is available in three types:

  1. Data file
    Intended for high-volume local use in environments where use of a Web service is impractical.
  2. Token-controlled query use
    Intended for Web sites and for-fee or private information services. Tokens enable a specific number of queries (e.g. 100,000 accesses) that have no time limits or expiration date.
  3. Single-host, IP address-controlled use
    Ideal for libraries and individual users. Your IP address is allowed a specific number of queries (e.g. 1,000 accesses) per day.

Review the xISBN subscription price list >>

How to order

You must first create a WorldCat Affiliate account. Have one already? Sign in to place an order.