I wanted to clear some room on my SSD, so I move a unity project over to hard drive. Now, opening the project again brings up warning message and I have to reimport that project. Go thorugh the green bar from hell.
What is happening here? Where are all the assets being imported too? I knew this would happen, but I don’t understand why.
I would assume that the green bar from hell leads only to the (n+1)th dimension of nonexistence.
On topic:
Honestly wish I knew. Though I’d actually assume Unity is just caching and recompiling meta files…
Yeah basically it’s doing that.
There are a few subfolders above the asset folder (i forget the names, obj and temp or something) - and Unity generates craploads of stuff that sit in those folders (they can grow to be 10 or 20 gigs iirc).
I’m not sure what all that stuff is, but most likely its just reprocessing all the assets into some kind of intermediate form so the editor can stay relatively snappy.
Yeah - the main folder is the Library folder, under which the ‘metadata’ folder can grow to be almost the size of the asset folder in total. Obj folder is the compiled c# code.
So, in other words, Unity is like your parents coming over and rearranging things to suit their liking, but you can’t say shit because your mother is very particular and if you want her to cook at all you gotta let her have her way.
Why can’t I like my own post?? We’re not allowed to be megalomaniacal here? 
Surprised I was smart enough to guess that was the case with the reimport stuff…
@BIGTIMEMASTER dude you read my mind. What the hell?? That is EXACTLY what my mom does. She even vehemently complains about my driver when she’s in the car with me, even though SHE taught me and I have had no collisions in my almost 10 year driving history.
Smart people never admit when they were guessing ^^^ 
Serious question though, is there a way to look up all dependencies up or down stream of an asset? Say I want to go through a third party tool and clear out non-essential stuff (like all the junk textures and skyboxes they come with), is there a way to do that without guessing?
the stuff in the library folder is ‘invisible’ to you, you will never actually touch any of it directly.
Sometimes, that folder will become f’d up, and the only way to deal with it is to delete it and let unity regenerate it (green bar from hell).
In terms of cleaning up asset folder, there are things in asset store that might fit. I’ve used a couple but never trusted any w/ deleting stuff from asset folder.
Oh, right. Obviously I must know everything and never guess. How could I have missed that…
Buf if you move the whole project folder then the existing cached stuff is already there. I just copied a whole project folder, and when I opened the copy it didn’t do any re-importing.
Runtime-format versions of them are being cached in the Library folder, which is inside your project folder. If this is being done again, there are a few possibilities I can think of:
Basically, the “Assets” folder is not your whole project. You need to copy the project folder, which is the parent of that, so that all of the derived data comes along for the ride.
I did move the entire project folder. I think something got bunged up with the target platform. I’m new to using unity hub and I think I may have swapped versions or something.