A node group won't go away despite being unused

There is a node group in one of my Blender files that refuses to be deleted despite not being used by any materials. The node group has no fake user. Yet, the outliner still states that the node group has one user. I have checked each individual material’s nodes for this stray group, finding that the group is not in any material’s nodes. How do I delete this group?

That’s a good question! I was about to suggest adding the node group to a material, then shift+clicking the X to remove it from all users, but it looks like node groups don’t have that X.

Change the outliner type to data-blocks, then expand node groups > your node group. The second line will show you how many users contain the group. That’ll at least tell you if you do indeed have it hidden away on an object somewhere. Beyond that, I’m not sure.

Check in Outliner: (Type of information to display:) Orphan Data > Uncheck Fake user > Purge All
Or look into Data-Blocks, Blender File…

Used in world nodes?

Whenever I localize all so I can take the project with me (linked library of useful functions), I have to do the “Purge, Save, Revert” thing many times while I observe in Orphan view that there is nothing more to purge.