Foundations

The handful of concepts you need to build with Node-RED, and how they fit together. You wire pre-built nodes into flows and spend your effort on the logic — what the system should do — while the platform handles the syntax and the connectivity. Learn these and you can build real integrations in Node-RED with only a little JavaScript — the structure carries most of the weight.

How it fits together

A message enters a flow and passes from node to node, transformed along the way, until it reaches a sink that sends and routes nothing. Reuse comes from subflows and link nodes; shared state lives in context; new capabilities come from installing nodes off the palette.

What it connects to

Node-RED's reach comes from its nodes: install one for a protocol or service and the instance can talk to it. The same runtime — a Hosted Instance in the cloud or a Remote Instance on your own hardware — reaches field hardware, databases, message buses, cloud services and other systems. And any instance can serve its own Dashboard for the people who use it.

The core pieces

• Node — A single processing block: it receives a message, does one thing — read, transform, call, route — and passes it on.
• Flow — Nodes wired left-to-right on a tab; a message enters, is transformed, and exits. One working unit of automation.
• Message (msg) — The object that travels the wires, carrying msg.payload plus metadata between nodes.
• Subflow — A block you define once and drop in many places, with its own inputs, outputs and per-instance config.
• Link nodes — link in / link out route messages across tabs with no visible wires; link call is the one that returns — your in-process service call.
• Context — Storage that keeps state between messages — flow and global scope, in memory or persisted.
• Palette — The library of installable nodes (npm) you add new capabilities from.
• Editor & runtime — The browser editor where you wire flows, and the runtime that executes them continuously.