Is None

"Is this thing connected, and does it actually have a value?" That's the whole question Is None answers, and it turns it into a BOOLEAN you can act on. One input, one output, and it's quietly the most useful little gate in this pack if you build branching workflows.

Here's the mechanic. In ComfyUI, an optional input you leave unwired simply isn't passed to the node - it arrives as None. So "not connected" and "connected to a node that produced None" look identical. Is None checks exactly that: plug anything into any_value (any type, optional), and IS_NONE comes back True if the input is unwired or if its value is None. False otherwise.

What you'd do with a boolean like that

Feed it into a switch. The classic build: a fallback-style switch that picks the first non-null input (rgthree's Any Switch is the canonical one) will automatically skip dead branches - but sometimes you want explicit control. Wire IS_NONE into an A/B selector or a logic node, and you can route around missing data deliberately: if the image load failed, take the blank branch; if the model loaded, skip the fallback. Pair it with None Primitive from this same pack and you can construct situations on purpose - a node that always emits None, gated by Is None, becomes a switch you control from the data instead of by bypassing nodes.

One subtlety that trips people: a legitimately empty value is not the same as None. An empty string "", an empty list, a zero - all of those are real values, and Is None will return False for them. If you need "is this string empty," this isn't the node; if you need "does this wire have anything at all," it is.

Inputs and output, complete list

• any_value - optional, any type. Connect whatever you want to inspect. Leave it unconnected and the answer is trivially True.
• IS_NONE - BOOLEAN output. True when the input is unconnected or None, False otherwise.

That's the whole node. No settings, no widgets, nothing to misconfigure.

Install

It's part of comfyui-sg-nodes by sebagallo. Install via ComfyUI Manager (search comfyui-sg-nodes) or:

cd ComfyUI/custom_nodes
git clone https://github.com/sebagallo/comfyui-sg-nodes

Restart ComfyUI; it appears under SGNodes/Utilities. No model downloads, no extra dependencies.