Back in 2020 we added MQTT support to curl.

When curl 8.19.0 ships in the beginning of May 2026, we have also added MQTTS; meaning MQTT done securely over TLS.

This bumps the number of supported transfer protocols to 29 not too long after the project turned 29 years old.

What’s MQTT?

Wikipedia describes it as a lightweight, publish–subscribe, machine-to-machine network protocol for message queue/message queuing service. It is designed for connections with remote locations that have devices with resource constraints or limited network bandwidth, such as in the Internet of things (IoT). It must run over a transport protocol that provides ordered, lossless, bi-directional connections—typically, TCP/IP.

Coming protocol support reduction

If things go as planned, the number of supported protocols will decrease soon as we have RTMP scheduled for removal later in the spring of 2026.