XMPP Core
XMPP powers enterprise messaging (Cisco Jabber), IoT device management, and many open federated chat systems. WhatsApp internally uses a modified XMPP protocol for message delivery.
What It Defines
XMPP (Extensible Messaging and Presence Protocol) is an XML-based protocol for real-time messaging. RFC 6120 defines the core: stream negotiation over TCP/TLS, stanza model (message, presence, iq), JID addressing (user@domain/resource), SASL authentication, TLS upgrading, and the stanza error model. XEPs (XMPP Extension Protocols) extend the core.
Canonical (Normative)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
The roster and subscription model in RFC 6121 defines how federated chat contacts work. Essential for implementing XMPP clients, servers, or S2S (server-to-server) federation between XMPP deployments.
Matrix is the modern alternative to XMPP for federated messaging: bridges to Discord/Slack/WhatsApp, end-to-end encryption by default, and full decentralization. Used by the German government, French public sector, and Mozilla.