The core specifications for XMPP are developed at the Internet Engineering Task Force (IETF). The XMPP Standards Foundation develops extensions to XMPP in its XEP series. Good places for developers to start are the compliance suites, as well as the technology overview pages. Basic XMPP RFCs RFC 6120: Extensible Messaging and Presence Protocol (XMPP): CoreRFC 6121: Extensible Messaging and Presence