Queue Previewer

Some nodes exist to change pixels. Queue Previewer exists to watch. It has no inputs, no outputs, and does nothing to your image - it's a resizable panel that shows the live preview stream right on the canvas, so you can keep a big eye on generation without hunting for the tiny Preview Image node at the far end of a sprawling graph.

How it works

The interesting part is how. This node is almost entirely JavaScript. The Python side is a stub - empty inputs, empty outputs, OUTPUT_NODE = True so ComfyUI doesn't prune a node that connects to nothing. The real work lives in the pack's web/preview_queue.js, which hooks into ComfyUI's b_preview websocket event - the same binary preview stream that fills the thumbnail preview in the corner of the UI. Every time a frame arrives, the node draws it into its own body. When the queue drains (queue_remaining hits zero), it clears back to a "Waiting for generation..." placeholder.

That mechanism also tells you its one honest limitation: it shows whatever preview frame the server last pushed, globally. It's not wired to a specific node. If you're running several Preview Image nodes, or a batch that streams frames, you see the latest one - not necessarily the one you care about. It's a monitoring panel, not a scoped monitor.

Should you bother?

Worth adding to your graph? It's a nice-to-have. If you work zoomed out on a big workflow, a live preview you can drag anywhere and resize beats squinting at the corner. If you already keep the built-in preview floating, it's redundant. There are no dependencies beyond the pack itself, and because there's no model or pixel math, it's the safest node in this suite to just add and forget.

Install and troubleshooting

Install is the standard pack route - ComfyUI Manager (search "comfyui-fams"), or clone the repo into ComfyUI/custom_nodes/ and restart. The frontend code loads automatically from the pack's web/ directory; nothing to configure.

One honest heads-up: the author left debug console.log calls in the extension, so open your browser devtools while generating and you'll see "Current Queue Remaining:" spam. Harmless, just noisy. And if the panel sits on "Waiting for generation..." forever, check that something is actually pushing a preview - no b_preview, no picture. That's the entire troubleshooting story.