All OpenURL requests made by end users via the Router at openurl.ac.uk are logged, and (subject to the metadata included by the referring service) provide a record of the article that user was attempting to find via their local resolver. The Router redirects these requests to the appropriate local resolver for each user, so though the Router logs each request, the ultimate outcome (whether the end user obtained a copy of the article, and from where) is unknown to the Router.
The OpenURL Router supports various types of requests other than links direct to local resolvers. These include the "lookup" requests (registry searches) and requests for the preferred button image to be used for each resolver. These requests are all logged, but they are not OpenURL requests and do not contain bibliographic metadata.
The OpenURL Router Data are thus data about traffic flowing through the UK OpenURL Router, and are sometimes known as activity data. The data are made publicly available so that other service providers may use them.