How can I find what uses an asset?

I'm cleaning up my project folder, and I'm trying to get rid of a few old unused assets.
The trouble is, I'm just not sure which ones are assets that something else is using.
This is particularly troublesome because I have a number of textures where I made alternate versions with different color variations, and I don't know which ones are used in a material.

There is an option to "find references in scene" that will reveal if anything in my current scene is using a given asset. But I'd like something a little more thorough; something to go through my whole assets directory, not just an open scene.
I thought "select dependancies" would show me something, but no matter what I use that on I only get a list containing just that asset itself.

Is there a way I can find everything that references a given asset? Every material, every prefab, every scene, etc.

 

There is no built-in tool for that since Unity only build the dependency tree upon build, so they can stay without meaningfully harm the project.
With that said, you can find some tools on the asset store which do what you described. I can't comment on them though, never used any of them. I usually organize as I go, keeping my project in one folder (well, the parts I add).

 

True, but I want to clean up and better-organize my project folder.