Microsoft's Unified Communication Web API (UCWA) REST API allows developers to modify their Enterprise applications using the Lync Server 2013's Instant Messaging and Presence capabilities. The API enables developers to add functions like anonymous web chat, multi-party instant messaging, and scheduling online meetings. The API also supports cross-platform communications across browsers and devices. It can be used from any language and any platform. Data is transferred with JSON or XML. Using the API requires that users have Lync on premises.