Win10 - Phantom used disk space

I'm trying to clean up my C: drive under Windows 10, and I keep running into disk space that is used up, but I can't figure out by what. Here's a prime example: Windows Explorer is telling me that the various profiles under C:\Users are using up a lot of disk space. But when I go into the individual folders, I can't find where all these GBs of files are hiding out. Depending on how I query the folders, I get different answers.

If I right-click C:\Users\UserA and go to Properties, the disk size is 32.4GB.

If I browse to C:\Users\UserA and select everything in there and right-click--Properties (adding up everything in the folder), the disk size is only 21.5GB.

Where are the other 11GB?

Another profile shows 8.42GB one way, but only 3GB if I add up everything in the folder.

Basically I have dozens of GB of used space that I can't find, and can't clear out. I keep maxing out my C: drive because of this. Disk Cleanup has not helped. Is there another better way to do this? Hoping to stop short of re-installing Win10.

Maybe hidden files or folders?

Download Treesize, let it run as administrator when it prompts. It will find everything.

Random question - are you using the Xbox app / Game Pass? That thing cleans up after itself like my 6 year old, and hides stuff it's installing / failing to uninstall in hidden folders.

I am not.

Treesize reveals that a lot of the hidden files are in Users\User\AppData, which contains what is probably a lot of bloat that some programs need, but not really. I was able to clear out a good 2-3 GB alone from deleting all the Chrome folders, since I haven't used Chrome in over a year. Deleting Chrome apparently didn't do anything for all of this data. I still have almost 10GB in that folder for Firefox, Microsoft, Steam, Epic Games, nVidia...I have no idea why these programs need so much data in these folders. I feel like there ought to be an option to go into all of them and clear out a cache or something, but that probably doesn't exist.

At any rate, Treesize helped a bunch - thanks.

You can probably delete some of that 10GB if you are careful - drill down to the largest folders then google for space issues relating to those folder names.

It’s common for Microsoft folder to bloat up with Outlook email folders or cached mailboxes. Temp files and crash report data can also build up, but disk cleanup should have cleared those.

A lot of Windows software these days stores stuff (including their own installs) within the user's AppData folder instead of asking for the permissions required for a global, Program Files folder install.

If you're careful about digging in there, you can probably kill off a lot of that stuff, but make sure you understand exactly what you're deleting before you kill it.

BTW, you can work with these files via the normal desktop by opening any Explorer window. You'll see a menu bar with File/Home/Share/View/Drive Tools. Click on View, over to the far right on Options, and then down to Change Folder and Search Options. A new window will pop up.

Go to the View tab (the second one), and a short distance down will be a heading for "Hidden Files and Folders". Click the radio button for "Show hidden files, folders, and drives." You probably also want to UNcheck "Hide extensions for known filetypes" a few down from there. Then you can click OK, and you'll be able to see C:\Users\username\AppData from Windows Explorer.

There's also an option for "Hide protected operating system files", and I usually leave that on. You generally can't touch or interact with those files directly, and they'll just clutter up the view.

AppData has three subdirs, Local, LocalLow, and Roaming. Apps can put data in any of these, and if you're trying to kill off the data from any particular program, you need to look in all three.

There's some differentiation between the three; Local is supposed to be for machine-local data, and Roaming is supposed to be in your global, roaming network profile on a Microsoft network. I don't remember what LocalLow is for. In actual practice, however, files can be anywhere, without apparent rhyme or reason. Each program will make itself a subdirectory, but some put it under a parent dir of the company making it, so you may have to dig quite a bit to figure out where any given program puts its settings. Some use more than one spot, so search through all three. Even if you find something in Local, there may still be data in LocalLow or Roaming.

edit: as Legion says, many programs actually install themselves in those dirs, too. Make sure to remove those through Add/Remove Programs first. Once the program is uninstalled, you can prowl through the AppData subdirectories and kill off any remnants.

I use Wiztree instead of Treesize, but shouldn't make too much difference. The other day I had just deleted a bunch of old games off my HD but was still running out of space. When I went into wiztree, I found my $Extend folder was pulling 100 GB for no apparent reason. It wiped itself on restart and I haven't had any trouble with it since, but I'd keep an eye on it if you're seeing weird drops in storage space. I suspect that it holds some sort of pagefile. Also suspect my habit of keeping open like 10,000 tabs might have fueled it.

I had a similar thing a few months ago, so I used WinDirTree or something similar to map the drive contents. Turned out that the entire download of Forza Horizon 4 was sitting there in a hidden directory of the C: drive, but completely invisible to the game pass app and Windows itself. Even better, it was locked behind edit permissions, so I had to do some funky reassigning of directory ownership before I could actually delete them. That was an 80gb mystery solved.