The OpenURL standard is a protocol for interoperability between an information resource and a service component. The underlying concept of the OpenURL standard is that links should lead a user to appropriate resources. A link server (such as SFX) defines the context of the user. When the link server accepts an OpenURL as input, it offers the user a range of services: such as links to licensed and/or free e-copies of full-text articles, physical library holdings information, docdel/ILL services, and a range of other services as defined and customized by the library.

The original OpenURL syntax was developed by Oren Beit-Arie of Ex Libris and Herbert Van de Sompel, now of Los Alamos National Laboratory; both Beit-Arie and Van de Sompel served on the NISO committee which developed what is now known as Standard Z39.88 (2004).

The OpenURL standard enables a user who has retrieved an article citation, for example, to obtain immediate access to the "most appropriate" copy of that object through the implementation of extended linking services. The selection of the best copy is based on user and organizational preferences regarding the location of the copy, its cost, agreements with information suppliers, and similar considerations. This selection is transparent to the user; it is made possible by the transport of metadata by means of the OpenURL link from the source citation to a "resolver" (the link server), which stores the preferences and the links to the appropriate material.

The initial development of the OpenURL standard - published as version 0.1 - was targeted at the electronic delivery of scholarly journal articles. In version 1.0, which is now the standard, the framework was generalized to enable communities beyond the original audience of scholarly information users to adopt extended linking services and lower the entry barrier for new implementers.

Many of today's information providers generate and output OpenURLs.

An information service that is OpenURL-aware must be able to distinguish between users who have access to a link server (such as SFX) and those who do not. The distinction can be made using a number of methods such as:

  • Identifying a user's IP address
  • Using information stored in a cookie (the CookiePusher mechanism)
  • Using information contained in a digital certificate, such as the one proposed by the DLF digital certificates prototype project
  • Obtaining user attributes via the Shibboleth framework

For users known to have access to an OpenURL-compliant link server, information providers must furnish an OpenURL for each object.

Note that an information service is not required to support the OpenURL standard in order to become an inbound Target of links (see a list of SFX Targets), although some providers do choose to incorporate the OpenURL standard or some of its elements into their inbound syntax.