Imprint - API Key

First, the name is a lie. This node doesn't call any API and it never needs you to paste a key into a field. All Imprint - API Key does is read an environment variable and hand the value to the other nodes in the ImprintAI pack that actually do the network work. It's a plumbing node - a very thin one - but it exists for a genuinely good reason.

ImprintAI is the provenance service behind this pack: you generate an image, it anchors a record of that generation to the Bitcoin SV blockchain, and you get back a transaction id (txid) that later proves what happened. Anchoring needs an account and an API key from imprintai.link. The pack's authors would rather you not type that key into a widget, because whatever you type into a ComfyUI node ends up embedded in the saved PNG's metadata by default - and that PNG is the thing you're about to share. One input string, shared workflow, and your key is traveling in the file with every download. So the recommended flow is to set the key once in the environment and keep it out of the graph.

What you get, what it takes

The input side is exactly one optional field: env_var_name, a string that defaults to IMPRINT_API_KEY. Leave it alone unless you've stored your key under a different variable. The output is a single string called api_key, which you wire into the api_key input of Imprint - Log Provenance or Imprint - Export Labelled PNG (+ C2PA).

Mechanically it's a one-liner: it reads os.getenv(env_var_name). If the variable isn't set you get an empty string and a console warning - no crash, which is a small trap in itself because the downstream nodes will then fail a step later with "No API key provided" and you'll chase the wrong node.

Setting the key up

Get an approved account and key from imprintai.link, then export it into the exact shell you use to launch ComfyUI:

export IMPRINT_API_KEY="your-key-here"
cd ComfyUI
python main.py

If you launch ComfyUI from a desktop launcher, a service script, or another machine's environment, the variable won't be there - put the export in whatever startup script actually starts ComfyUI, and restart ComfyUI fully after changing it.

Installing

This pack isn't on the ComfyUI Registry yet (the README says publication is waiting on an immutable publisher identity), so ComfyUI Manager probably can't find it by search - that's not a typo on your part. Install it manually:

cd ComfyUI/custom_nodes
git clone https://github.com/svcBSV/imprintai-comfyui.git
cd imprintai-comfyui
python -m pip install -r requirements.txt

Restart ComfyUI completely. Dependencies are just requests and Pillow, both of which ship with ComfyUI anyway, so this is the rare custom node with nothing heavy to fetch. The README is blunt about one thing: because the Registry listing isn't live, don't trust a similarly-named unofficial package - install from this exact repo.

Where people get burned

The usual failure is that the environment variable is set in your login shell but not the process running ComfyUI, so the node silently returns empty and the workflow dies at the anchor step with a confusing error. Test it in the same shell first with echo $IMPRINT_API_KEY. And remember this node is optional in one sense - ImprintLog and ImprintExportC2paPng both fall back to the same environment variable if you leave their api_key inputs blank. The node mainly earns its place by making the credential visible in the graph as an explicit wire, and by letting you point at a differently-named variable without editing every node.