🔧 Console Debug

When a graph is doing something weird and you genuinely don't know what's flowing through a given wire, Console Debug is the fastest way to find out. Clip it onto any connection - it accepts literally anything, typed as * - and it prints what's actually passing through to your ComfyUI console, without breaking the rest of the graph, because it doesn't need to sit at the end of anything.

How it works

value takes any type at all. prefix (optional STRING, default "Value:") is printed before it, which matters more than it looks once you've got three or four of these scattered around a busy graph - set a distinct prefix on each so you can tell which one fired in the console log. It has no outputs at all; it's a pure side-effect node, and is_output_node: true means it actually executes when the graph is queued instead of getting silently pruned as "unused" the way a dead-end node with no consumer normally would.

Inputs and outputs

Required: value (any type). Optional: prefix (STRING). No outputs.

Installing it

Via ComfyUI Manager, search "ComfyUI Essentials". Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/cubiq/ComfyUI_essentials

Restart. Maintenance-only pack since April 2025 - for a node this simple, that barely matters.

Common issues & troubleshooting

Nothing seems to happen when the node runs. That's the point - it has no outputs and does nothing visible on the canvas. The payoff is in your terminal or server console, not the graph UI. If you're staring at the node waiting for something to change on screen, you're looking in the wrong place.

Can't find where the output actually printed. If you're running ComfyUI as a background service or through a process manager, the console output goes wherever that process's stdout/stderr is being captured - not necessarily the browser window you're looking at. Check wherever you'd normally see ComfyUI's own startup logs.

Debugging a busy graph with multiple debug nodes and can't tell them apart. Set a distinct prefix on each one before you start - "why is this happening" debugging gets a lot faster once each printed line tells you which node it came from.

Wanted to inspect something without touching Python. This is exactly that use case - cheaper and faster than adding a print statement to custom node code, and you don't need to edit anything outside the graph.