Preview Image (Queue)

Every ComfyUI user knows the feeling: you've built a twelve-node workflow and you just want to check whether this one image-processing branch works before committing to the full 40-minute generation. The built-in PreviewImage node can't do that by itself - running it queues your whole graph. Preview Image (Queue) adds a button on the node that queues just this node and its dependencies, so you can test a sub-branch in isolation. It's a quality-of-life node, and honestly it's the kind of thing that should be in core ComfyUI.

How it works

On the Python side it's a subclass of ComfyUI's own SaveImage that writes to the temp directory with a random suffix - so previews behave like normal previews and don't clutter your output folder. The interesting part is the JavaScript: the node draws a small queue button, and clicking it walks your graph backwards, collecting every node that feeds into this one, then queues only that subset. That's the whole trick - recursive dependency collection plus a targeted queue call.

The node also passes images through on its output, which sounds redundant for a preview node but matters: it means you can place it in the middle of a chain as an inspection point without breaking the flow.

The inputs and outputs

• images - the only required input, an IMAGE.
• images - the output, an IMAGE passthrough.

That's it. One in, one out, plus the button.

Where you'd reach for it

• You're iterating on a crop → process → uncrop pipeline and want to eyeball the crop node's output without running the sampler.
• You're tuning a mask and want to see the mask's effect without a full generation.
• Any "did this actually work?" checkpoint in a long graph.

It's the ComfyUI equivalent of a print() statement you can see, and for debugging graph branches that's worth more than it sounds.

Installing it

Ships in Pirog's Nodes:

cd ComfyUI/custom_nodes
git clone https://github.com/Pirog17000/Pirogs-Nodes
pip install -r Pirogs-Nodes/requirements.txt

Or search "Pirog's Nodes" in ComfyUI Manager and restart. The queue button is front-end code, so a hard refresh (Ctrl+Shift+R) after installing is a good idea if the button doesn't appear.

Gotchas

The button is a convenience, not a different execution engine - your sub-branch still needs all its inputs satisfied, so a preview node mid-graph with inputs dangling upstream of a missing node won't queue cleanly. And because it writes to the temp folder, the previews are subject to ComfyUI's temp cleanup; if you need a permanent copy, use the regular save node. Minor stuff, which is the point - this is one of the pack's "small details that make big differences" nodes.