Live Preview (Large)

If you've ever dragged the corner of your KSampler node out to comical proportions just to get a slightly bigger view of the built-in preview thumbnail, this node is what you actually wanted. Live Preview (Large) pops a big, floating, draggable window over the ComfyUI page that shows your image forming step by step - the live-denoising view A1111 and Forge users have had for years, bolted onto Comfy's graph instead.

Why this exists

ComfyUI won the UI wars on power and reproducibility - the node graph lets you build things a form-based UI like A1111 simply can't represent, and a workflow doubles as a shareable PNG. But it gave something up to get there: A1111 put the live preview front and center as you generated; ComfyUI tucked it into a small thumbnail inside the sampler node, easy to miss on a busy graph. This pack is a straight fix for that one regression - it doesn't touch your pipeline, it just gives you back the big preview.

How it actually works

The README is blunt about this, and it's worth believing: "zero overhead - hooks into ComfyUI's existing websocket preview stream, no extra processing." ComfyUI already broadcasts step-by-step preview frames over its websocket while a KSampler runs; the built-in UI renders those into that small thumbnail. This node's frontend JS just listens to the same stream and renders it into a large, resizable overlay instead - draggable by the header, resizable from the corner, positioned wherever you like. The header shows a step counter and an FPS readout, plus a status dot: green while generating, purple once done. A persistent ⚡ button sits in the bottom-right corner of the page so you can toggle the window at any time - including after generation finishes, if you just want to glance back at the last preview.

Inputs and outputs

There's exactly one input and one output, and both are the same type:

• images (IMAGE, required) - wire in wherever you'd normally send an image, e.g. straight off a VAE Decode.
• images (IMAGE, output) - passed straight through, unchanged.

That's the whole schema - no tooltips, no optional knobs, nothing to tune. It's genuinely a pass-through: whatever comes in goes out untouched, so you can splice it into an existing chain (VAE Decode → Live Preview → Save Image) without disturbing the rest of the pipeline. The README also says you can leave it floating unconnected anywhere in the graph and it'll still activate the overlay - which tracks with how it's built: the live frames come off the websocket stream ComfyUI already sends, not from the images tensor itself, so the node's real job is just marking "a Live Preview node exists here" for the frontend to notice. If you want it guaranteed to run every time rather than possibly get pruned as unused, wiring it inline is the safer habit.

Installing it

Two options, both trivial:

• ComfyUI Manager - search for "ComfyUI Live Preview" (or the node's display name, "Live Preview (Large)"), install, restart.
• Manual - cd ComfyUI/custom_nodes && git clone https://github.com/TechnoWarrior2/comfyui-live-preview, then restart ComfyUI. (Or grab the ZIP from GitHub and drop the folder into custom_nodes/ yourself.)

There's nothing else to it - no model downloads, no Python dependencies to fight with. It's a small frontend extension plus a one-input pass-through node, about as low-risk as a custom node install gets. Find it afterward by searching "Live Preview (Large)" in the node menu, filed under image.

Troubleshooting

The one real gotcha, called out directly in the README: ComfyUI has to have previews enabled at launch for any frames to broadcast over the websocket at all. If your overlay window opens but stays blank or never updates, check your launch arguments - you need --preview-method auto (or latent2rgb / taesd) rather than --preview-method none. Since this node just rides the existing preview stream, if your built-in tiny thumbnail is already blank, the big overlay will be blank too - the flag is the actual fix, not the node.

Beyond that, the window only activates when a Live Preview node is somewhere in your current graph - delete or bypass it and the ⚡ toggle has nothing to show. And don't expect the node to do anything to your image: it's a passthrough, so if you're chasing a color shift or quality change elsewhere in the pipeline, this isn't the place to look - the images output is bit-identical to whatever went in.

It's a small, single-purpose pack from a maintainer without much of a track record yet, so treat it like any fresh node: works as advertised today, but there's not much community mileage on it to fall back on if something breaks after a ComfyUI frontend update.