YAZ is a toolkit for the development of client and server software built around the ANSI Z39.50 (ISO 23950) standard for information retrieval.

YAZ supports Z39.50-2003 (version 3), SRU versions 1.1 to 2.0, and the industry standard ZOOM API for Z39.50.

The yaz-illclient program is a command-line client that sends ISO ILL requests to a server and decodes the response.