A deep-linking URL is the way a library link within WorldCat.org results takes a user directly to an individual item's record within your online catalog (OPAC). In order for this to occur, the "syntax" of deep links for your particular OPAC must be registered with OCLC in the WorldCat Registry > Online Catalog section of OCLC Service Configuration.
A deep link's syntax is the basic structure of the link, focusing on where standard identifier information about the searched item (e.g. ISBN) is embedded within the URL. A sample deep link syntax is shown below:
The "library_opac_baseURL" portion of the URL above would be replaced with the base URL for your library's OPAC (e.g. "catalog.mylibrary.org"). In the instance shown above, the standard identifier is an ISBN, and is passed from WorldCat.org to your OPAC with an ISBN appended after the "=" sign at the end.
If your library has not registered its deep-linking syntax for your OPAC with OCLC, WorldCat.org users do not reach the individual item record; rather, they reach the main search page for your library's OPAC, where they must repeat their search. Please consider that the continued success of this kind of access to library content depends in part on OCLC member libraries guiding Internet searchers directly to item records.