Debug Print

The single most common "why is my workflow broken" answer is: what is actually flowing through this wire? Debug Print answers that. You drop it anywhere in the graph, it prints the value and its type to the ComfyUI terminal, then passes the value through untouched so you don't have to rewire anything around it. It's the console.log you wish the core graph shipped with.

It's part of DebugPadawan's ComfyUI Essentials, a small MIT-licensed utility pack. The node's AnyType plumbing is openly borrowed from pythongosssss's ComfyUI-Custom-Scripts (the source says so), which is a good sign - that's the trick that lets one node accept literally any type.

How it works

The value input is a wildcard (*), so it accepts images, latents, strings, numbers, lists, whatever. At execution it prints a line like this to the server console:

[MyLabel] list: ['Element1', 'Element2', 'Element3']
[Debug] str: Hello World
[Checkpoint] int: 42

The format is [label] typename: value. The label input (default "Debug") is your friend - when you've got six of these in a graph, labels are the only way to tell them apart.

The output, passthrough, is the exact same value. That's what makes it useful mid-pipeline: you can tee off a wire, log it, and the original flow keeps going.

The big gotcha: where the output goes

The print lands in the ComfyUI terminal / server log, not on the canvas. If you're running a hosted service or a desktop build where you can't see the server console, this node prints into the void and you'll think it's broken. In that situation you want a Show Text-style node that renders on the canvas instead. In a normal local install, though, this is the fast path: check the terminal window you launched ComfyUI from.

Install

Standard custom-node fare:

cd ComfyUI/custom_nodes
git clone https://github.com/DebugPadawan/DebugPadawans-ComfyUI-Essentials.git

Restart ComfyUI, or install via ComfyUI Manager by searching "DebugPadawan". requirements.txt lists numpy, torch, and opencv-python - numpy and torch already ship with ComfyUI and the shipped code never imports cv2, so there are no heavy downloads, no model files, no API keys.

Using it well

Community debugging doctrine is "change one variable at a time with a fixed seed." Debug Print is the tool that makes that doctrine usable - print the seed, print the conditioning size, print whatever list you suspect is empty. One honest tip: print types, not just values. Half the time the bug is "this is a list of floats, not a list of strings," and Debug Print shows you that in one line without any guessing.