Nor

Nor is the strictest gate in the set: it returns true only when neither input is true. Where Or says "any of these," Nor says "none of these." It's the boolean you reach for when a workflow should take the special path only if no trigger is active - a clean "do nothing unless told otherwise" condition that's surprisingly rare to find spelled out as a single node.

It's part of marco-zanella's ComfyUI-BooleanExpression pack, a dependency-free logic collection that ships the full gate set (And, Or, Xor, Nand, Nor) so you don't have to staple a Not onto an Or. Nor is literally not (first or second) - Or's permissiveness, negated.

How it works

Two required inputs, both BOOLEAN and both defaulting to true:

• first - the first boolean value
• second - the second boolean value

Output is nor, a BOOLEAN: not (first or second). One line of Python. Truth table: false, false, false, true - the only passing case is when both inputs are false.

The natural use: "if neither condition applies, fall through." Two comparison checks - "is it high-res?" and "is the batch big?" - feed a Nor, and the output is true only for the plain, default case. Pipe that into a Conditional Branch and you've got "keep it simple unless there's a reason not to." It's the polite, default-respecting gate.

Installing it

No models, no dependencies, pure Python - the pack's requirements.txt is empty. ComfyUI Manager, search ComfyUI-BooleanExpression, or:

cd ComfyUI/custom_nodes
git clone https://github.com/marco-zanella/ComfyUI-BooleanExpression.git

Restart ComfyUI, and it's under Boolean Expressions.

Gotchas

• The defaults bite in reverse. Both inputs default to true, and not (true or true) is false - so a fresh Nor node is off until you wire real values in. If your workflow "doesn't do the default thing" after adding a Nor, this is why.
• Nor is not Or. The names rhyme and the shapes match, but the truth tables are opposites. If a branch flips behavior, check you didn't grab the wrong gate - it's the single most common mix-up in this family.
• It selects a value, not a path. Like every gate here, Nor just produces a boolean; both input chains of any downstream Conditional Branch still compute. Free for booleans.
• Juggling multiple gates? Binary Expression in the same pack collapses and/or/xor/nand/nor into one dropdown. Dedicated nodes read better in shared workflows; the dropdown wins for tinkering.

Nor is the least-loved gate in the pack, and honestly it's fine - most workflows never need "none of these." But when you're building a careful default-first workflow, it's the node that says exactly what you mean in one word.