Node-RED

Node-RED is a browser-based flow programming tool where nodes are dropped onto a canvas and connected to describe how events move through a system. It ships nodes for HTTP, MQTT, serial ports, databases, message brokers, cloud services and common hardware, and functions can be written inline in JavaScript when a standard node is not enough.

It is a favourite in home labs and IoT projects for connecting sensors, lights and notifications, and in operations for bridging legacy devices into modern message buses and dashboards.

Running it yourself means the traffic flowing between your devices and services stays on your network, there is nothing to pay per device or user, and saving the flow editor contents as JSON gives you a complete, restorable version of every automation.