File Exists 🐑

Does this file exist? Yes or no. That's the entire node - and it's more useful than it sounds. FileExists takes a path and returns a boolean, which is exactly the primitive you need to build caching and skip logic into a ComfyUI graph: check whether an output already exists, and branch on the answer so you don't regenerate something you already have.

Part of ComfyUI-MieNodes (ComfyUI_MieNodes), MieMieeeee's utility pack, in the Common group.

Why you'd use it

ComfyUI has its own execution caching, but it doesn't know about your files. If you're running an expensive step - a long video render, a big generation - and you've already produced the output once, you'd like to skip it on the next run. To do that you need a way to ask "did I already make this?" and act on it. FileExists is that question, expressed as a wire.

The default value in the node is telling: output/cache/abc.mp4. This is built for caching. The intended pattern is to compute a deterministic filename for a piece of work - often a hash-based name, which is what the pack's ImageHash and StringHash nodes exist to produce - then check whether that file is already on disk before spending the compute to create it. If exists is true, route around the heavy node; if false, run it. It turns a filename convention into a genuine skip-if-cached switch.

The inputs and outputs that matter

One required input:

• file_path - the path to check (default output/cache/abc.mp4). Feed it a computed cache path or a literal one.

One output:

• exists (BOOLEAN) - true if the file is there, false if not.

Wire exists into whatever consumes a boolean in your branching setup - a conditional/switch node, or a trigger_signal on another MieNodes node - to decide whether the expensive branch runs.

Installing it

ComfyUI Manager → search ComfyUI-MieNodes → install → restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/MieMieeeee/ComfyUI-MieNodes

then restart. No model download. Nodes appear under the 🐑 MieNodes menu.

Common issues

It only reports; it doesn't branch. FileExists gives you a boolean and nothing more. The actual "skip this" behavior comes from whatever you wire the exists output into - a switch, a conditional, a gate node. This is the sensor, not the valve.

Relative vs absolute paths. The default is a relative path (output/cache/abc.mp4), which resolves against ComfyUI's working directory. If your files live elsewhere, use an absolute path so there's no ambiguity about where it's looking.

Caching needs a stable filename. The whole pattern falls apart if the filename isn't deterministic - check-then-generate only helps when the same input produces the same path every time. That's why it's usually paired with a hashing node (ImageHash / StringHash) that turns your inputs into a stable cache key. A random or timestamped name will never be found.

Serverless caveat. On a cloud/serverless ComfyUI the filesystem is often ephemeral, so a file "cached" on one run may be gone on the next. This caching trick works best on a local install with a persistent output folder.