🪛 Preview from image

A preview node that shows you an image mid-graph plus the current run's metadata, and - the actually useful bit - caches what it shows, so you can disconnect it and still see the last image and its data to compare against a new run. Crystian built the whole metadata half of this pack around exactly that comparison instinct: his own README says the metadata comparator node was "the main reason" he made the extension at all.

Why you'd reach for it

Drop it after a sampler or upscaler to eyeball output without a separate Save Image step cluttering your output folder. But the real trick is the cache: run your graph, note the seed/steps/cfg shown, tweak your sampler settings, run again, and you can compare the new preview against the still-visible cached one - no need to keep two branches open side by side.

How it works

There's a genuinely important gotcha in how this node gets its data, straight from the README: to preview anything, ComfyUI has to save the image to a temporary folder first, and the metadata shown reflects that temp file and the current prompt run - not necessarily the original embedded metadata if the image came from somewhere else in your graph (say, loaded and then modified). If you need the real, original metadata of a loaded image, this is the wrong node - that's what Load image with metadata is for.

Inputs and outputs

One optional input: image - any image link in your graph. One output: Metadata RAW, which you can feed into Metadata extractor to pull out the prompt, file info, or raw formats, or into a metadata comparator to diff against another run.

Installing it

Through ComfyUI Manager, search crystools. Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/crystian/ComfyUI-Crystools.git
cd ComfyUI-Crystools
pip install -r requirements.txt

Restart ComfyUI. No models needed, just the pack's own lightweight dependencies.

Common issues

The cache is explicitly not permanent - it's on the author's own to-do list to fix ("survive to F5 or restart the server"), so don't count on it surviving a browser refresh or a server restart. If you need a comparison to persist across a session, save the images properly instead of relying on this node's cache.

And again: the metadata here is the current prompt's, tied to the temp save, not the image's original embedded data. It's easy to assume "preview" means "show me what's really in this file" - it doesn't, and mixing that up is the single most common way people misread this node's output.

Beyond that, this pack's nodes have a known pattern of disappearing or throwing IMPORT FAILED in the console after a ComfyUI update - a dependency resolution issue, not something wrong with your workflow. If the node vanishes from your menu, check the startup log and reinstall the pack.