Boolean Not (mtb)

There's not much to explain about a node that inverts a boolean, and that's kind of the point of writing about it - this is the one-line utility node from MTB Nodes' mtb/utils category that you install the whole pack for other reasons and then quietly reach for constantly, because ComfyUI's graph logic is entirely wire-driven and sometimes what you need is just "the opposite of this toggle."

Why this earns a place in your graph

ComfyUI doesn't have an inline "not" operator on a wire - booleans are values that travel between nodes like anything else, and if two branches of your workflow need opposite conditions off the same underlying toggle, you either duplicate the checkbox and remember to keep both in sync by hand (a recipe for a graph that silently drifts out of sync after your third edit), or you drive one from the other with a Not node. This is that node. Flip one switch, and both the "if true" and "if false" branches of your workflow stay correctly wired to a single source of truth.

Typical use: a single "use ControlNet" checkbox feeding a Switch node that needs the inverse condition on its other input, or gating two mutually-exclusive branches (say, "load from URL" vs. its opposite, "load from disk") off one toggle instead of two.

The input and output

• bool_in (default false) - the boolean to invert.

Output: inverted_bool - exactly what it says. true in, false out, and back again.

Installing it

ComfyUI Manager: search MTB Nodes, install, restart. By hand:

cd ComfyUI/custom_nodes
git clone https://github.com/melMass/comfy_mtb

then restart ComfyUI. Nothing to download, no dependencies of its own - it's a single Python function.

Common issues

Realistically, there's nothing this specific node can go wrong on its own - it's a boolean flip. The only thing worth flagging is pack-wide: MTB is a large pack, and it doesn't hard-fail if one of its many other nodes can't import on startup. It logs a line like [comfy_mtb] Some nodes (N) could not be loaded. This can be ignored, but go to http://127.0.0.1:8188/mtb if you want more information and keeps the rest of the pack - including simple utility nodes like this one - running fine. That's a real behavior confirmed in other users' install logs, not a hypothetical, so if you install MTB Nodes and Boolean Not (or anything else from the pack) doesn't show up in your node search, check that console line before assuming the clone or install failed. It almost always points at one specific missing dependency for a different, heavier node, not a problem with the whole pack.