What are Nodes?
Nodes are the Workers
Section titled “Nodes are the Workers”In ComfyUI, nodes are the basic units that do the work. Some are official Comfy Core nodes, some are community-built custom nodes — each has its own job.
Nodes are connected to each other via links, like people meeting: some pair up naturally, others just can’t connect. When two types don’t match, don’t force it — just swap in a compatible node.
Take the KSampler node: it has multiple inputs, outputs, and a bunch of parameters. How you set those parameters determines what that node computes. The logic is written Python under the hood; you generally don’t need to touch code — just configure things in the UI.
More Precisely: Nodes are “Operators” in a Graph
Section titled “More Precisely: Nodes are “Operators” in a Graph”In a graph, nodes rarely float alone — they’re usually connected in a network. In ComfyUI, they’re the boxes on the canvas.
They work more like function operators: take in data, process it by rules, pass results forward. To run an image generation task, nodes are the pieces that actually do the work. So nodes almost always have at least one input or one output, and many have multiple ins and multiple outs.
Node States: Spot Problems at a Glance
Section titled “Node States: Spot Problems at a Glance”When running a workflow, nodes show different states. Common ones:
- Normal: Default — not running, or finished without errors.
- Running: Currently executing after you hit Run.
- Error: Finished but something’s wrong, usually a bad input; the problematic input is typically highlighted in red — fix it and re-run.
- Missing: Common when importing someone else’s workflow:
- Missing core node: Your local ComfyUI version is likely too old — try updating ComfyUI.
- Missing custom node: The workflow uses a third-party node you haven’t installed. Use ComfyUI Manager to search and install by name, or follow the official “install custom nodes” guide.
Wiring: Only Matching Types Connect
Section titled “Wiring: Only Matching Types Connect”Nodes pass data between each other via links; types must match to connect two nodes.
No need to memorize everything — think of it like a color-matching game. Same-color ports can connect.
The UI uses color to distinguish common data types. A rough reference:
| Data Type | Color |
|---|---|
| Diffusion model | Lavender |
| CLIP model | Yellow |
| VAE model | Rose |
| Conditioning | Orange |
| Latent (latent image) | Pink |
| Pixel image | Blue |
| Mask | Green |
| Number (int / float) | Light green |
| Mesh | Bright green |
New types may be added over time — check the software for the latest.
To connect: drag from a node’s output port to another node’s same-color input port.
To disconnect: click and drag from the input end of a link, or click the midpoint of a link and select disconnect.
Can I Customize the Appearance?
Section titled “Can I Customize the Appearance?”Yes. Nodes are boxes and you can:
- Change style and color
- Double-click the title to rename it
- Drag the corner to resize