Comparing Two Frames ♾️Mixlab

Sometimes you just want to look at two images side by side without tabbing out to an image viewer or building a grid. Comparing Two Frames is exactly that: hand it a before image and an after image, and it renders them as an interactive comparison inside the node itself, right there in the ComfyUI canvas. It's a dead-end node on purpose - it has no data outputs, because its entire job is to be looked at, not to pass anything further downstream.

Mixlab's README mentions comparison as a recurring theme - "PromptImage & PromptSimplification, assist in simplifying prompt words, comparing images and prompt word nodes" - and this is the plain image-versus-image half of that family, without the prompt-pairing baggage.

How it works

You wire two images in and the node draws them as a comparison view - the standard drag-slider-to-reveal pattern most image-diff tools use. There's no processing happening here beyond rendering; it doesn't compute a difference map or a similarity score, it just gives you eyes on both images at once.

The inputs and outputs that matter

Two required inputs, nothing else:

• before_image (IMAGE) - the reference frame.
• after_image (IMAGE) - the one you're checking against it.

There are no outputs. This is marked as an output node - it renders in the UI and terminates the branch it's on.

How to install it

Ships with the Mixlab pack.

• ComfyUI Manager: search comfyui-mixlab-nodes, install, restart.
• Manual: cd ComfyUI/custom_nodes && git clone https://github.com/shadowcz007/comfyui-mixlab-nodes.git, install requirements (install.bat on Windows, or ../../../python_embeded/python.exe -s -m pip install -r requirements.txt), restart.

Nothing to download for this one - it's a pure viewer.

Common issues & troubleshooting

I tried to wire something after it and couldn't. That's expected - it has no outputs at all, so it belongs at the end of a branch, not in the middle. Use it for "let me look at this" moments: original vs. upscaled, seed A vs. seed B, before vs. after a compositing step.

The comparison looks off / misaligned. These viewers generally work best when both images are the same resolution or close to it - if before_image and after_image come from very different pipeline stages (say, a small preview versus a full-res render), expect the compare view to look mismatched even though nothing is technically wrong.

It's not doing anything measurable. Correct - it's not meant to. If you need an actual numeric or pixel-diff comparison rather than a visual one, this isn't the node for that; it's purely for eyeballing.