The core of the protocol is specified in RFC 7252. Various extensions have been proposed, particularly:
* [https://datatracker.ietf.org/doc/html/rfc7641{{IETF RFC|7641]}} (2015) Observing Resources in the Constrained Application Protocol
* [https://datatracker.ietf.org/doc/html/rfc7959{{IETF RFC|7959]}} (2016) Block-Wise Transfers in the Constrained Application Protocol (CoAP)
* [https://datatracker.ietf.org/doc/html/rfc8323{{IETF RFC|8323]}} (2018) CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets
* [https://datatracker.ietf.org/doc/html/rfc8974{{IETF RFC|8974]}} (2021) Extended Tokens and Stateless Clients in the Constrained Application Protocol (CoAP)