OpenURL is a standardized format for encoding a description of a resource within a Uniform Resource Locator (URL), intended to help Internet users to find a copy of the resource that they are allowed to access. Although OpenURL could be used with any kind of resource on the Internet, it is usually used by libraries to help connect patrons with such content as articles, books, or patents held in their collections or available by subscription. The National Information Standards Organization has developed standards for OpenURL and its data container (the ContextObject) as American National Standards Institute standard ANSI/NISO Z39.88-2004.
The OpenURL standard is designed to enable linking from information resources such as abstracting and indexing databases (sources) to library services (targets), such as academic journals, whether online or in printed or other formats. The linking is mediated by "link resolvers", or "link-servers", which parse the elements of an OpenURL and provide links to appropriate targets available through a library by the use of an OpenURL knowledge base.