Discovery Services enable OPC UA Applications to locate other OPC UA Applications. For example, a Client application can use a Local Discovery Server (LDS) to find Servers on the local network. In a larger, more complex network, a Global Discovery Server (GDS) might be used to discover Servers across different network segments. The Client sends a Discovery request, and the Discovery Server responds with a list of available Servers and their connection details.

OPC UA defines three levels of dedicated Discovery Servers:

1. Local Discover Servery (LDS)
2. Local Discovery Server with multicast extension (LDS-ME)
3. Global Discovery Server (GDS)

OPC 10000-12 describes how to use the Discovery services with dedicated Discovery Servers.