NOT

NOT takes a single boolean and returns its opposite. If True goes in, False comes out; if False goes in, True comes out. That's it - and if you've ever spent ten minutes staring at a workflow trying to figure out why a branch runs when you thought it shouldn't, you know exactly why this tiny node earns its place.

Why you'd reach for it

Almost every conditional workflow needs an inversion at some point. The classic pattern: a node gives you a boolean that means "this condition was met," but the branch you're building needs the opposite - "do this only when the condition was not met." Instead of reworking upstream logic, you drop a NOT between them and move on.

It pairs constantly with switch nodes from this same pack. You might have a "face detected" flag feeding a switch, but want the other branch when no face was found. NOT on the flag flips the switch's behavior cleanly. It's also how you build more complex gates: NAND is literally an AND feeding a NOT, and you'll often see people compose the primitive gates this way rather than hunting for a specialized node.

The take: NOT is one of the three logic nodes you'll actually use daily, alongside OR and AND. If you're only going to install one thing from SimpleLogics, this plus a switch node covers a shocking amount of workflow logic.

How it works

It's Python's not a - a single boolean in, a single boolean out, no state, no dependencies, nothing clever. The author's description: "Returns the opposite boolean value of the input." It's in the SimpleLogics/Logic category with the rest of the gates.

The inputs that matter

Just one:

• a - the boolean you want to flip (required, BOOLEAN, defaults to False)

One BOOLEAN output. Wire it into a switch's condition, chain it into other gates, or use it to invert a compare result before it hits your routing logic.

Installing it

Comes with danipisca07/ComfyUI-SimpleLogics, the small pure-Python pack with zero dependencies - no requirements.txt, no model files, nothing to download. Install via ComfyUI Manager (search "SimpleLogics") or:

cd ComfyUI/custom_nodes
git clone https://github.com/danipisca07/ComfyUI-SimpleLogics

Then restart ComfyUI. Done.

Common issues

The only way to trip over NOT is to misread the flow: a boolean flipping can look like a wiring bug when you're not expecting it. If a branch runs when it shouldn't, trace the booleans back and look for an unexpected inversion - it's usually the NOT, not a broken node. One pack quirk to remember: installing SimpleLogics also registers an unrelated GeoCalib-to-fSpy camera node that the README doesn't document; ignore it. Otherwise there's genuinely nothing to troubleshoot on a one-input gate.