MF Show Data

The most common debugging question in ComfyUI is "what is actually in this wire?" - because half the time it's not what you think, it's an error string or an unexpected format that your next node silently accepts. MF Show Data (MF_ShowData) is the answer: drop it anywhere in a string path, and it displays the exact contents in a read-only widget on the node, prints the same text to the console, and passes the data straight through. From the MF PipoNodes pack (pierreb-mf / Moment Factory).

How it works

One required input, one output:

• data (STRING, forced input) - whatever string you want to inspect.
• data (STRING output) - the same value, unchanged, so the node never interrupts your flow.

You literally splice it between two nodes:

LLM node ──▶ MF Show Data ──▶ Save/Next node
                  │
                  ▼
          (widget shows the text)

The display widget auto-sizes between 5 and 25 rows based on content length (the shipped code clamps there, despite docs that claim 3–20) and uses a monospace font, which makes JSON and structured text actually readable. It also prints the contents to the ComfyUI console with divider lines - useful when you want the value in the terminal for copy-pasting.

Two small details worth knowing. First, the node strips markdown code fences (```json ... ```) from the input before displaying and passing on - same helper as MF Save Data, so LLM output with fences reads clean and flows clean. Second, it's an output node, so it always executes and the widget updates on every run; there's no caching trap where you stare at stale data.

When you'll actually reach for it

• LLM output inspection. Feed the raw response in, confirm it's valid JSON before it hits a parser. This is the single most common use.
• Debugging transformations. Validate what a string-manipulation node produced before you trust it downstream.
• Verifying saved data round-trips. MF Read Data → Show Data → eyeball the load before it feeds a workflow.

It's the cheapest possible version of "print debug the graph" - no console hunting, no JSON-in-image metadata decoding, just look at the node.

Install

cd ComfyUI/custom_nodes/
git clone https://github.com/pierreb-mf/ComfyUI-MF-PipoNodes
cd ComfyUI-MF-PipoNodes
pip install -r requirements.txt

Restart after, or ComfyUI Manager → "MF PipoNodes". Only aiohttp and pyyaml; nothing to download.

Gotchas

• It only shows strings. Feed it an image or a mask and there's nothing to display - the node accepts STRING only, so for non-text debugging you'll want a preview node instead.
• The display is read-only - you can't edit the value in the widget. If you need to tweak a string mid-flow, that's a text-manipulation node's job, not this one's.
• If the widget doesn't appear or doesn't update, check the browser console for a JS error - the pack's frontend extension is the part most likely to break across ComfyUI frontend updates.