AppData is eating your C: drive: how to find what is big and what is safe to clear

If your C: drive is full and you can't work out why, check AppData. It is hidden by default, it holds data from every app you have ever installed, and Windows never shows you a total for it. Here is how to measure it, what usually lives in there, and how to clean it without breaking anything.

What the three folders are

Windows has three per-user AppData folders (Known Folders):

The notes on what each one is for come from Microsoft's community answers on Local, LocalLow and Roaming. In practice the big stuff is almost always in Local. You can open it by pasting %LOCALAPPDATA% into the File Explorer address bar.

Step 1: find the biggest folders

File Explorer won't show folder sizes, so measure them. This script adds up every top-level folder in Local and shows the 15 biggest. -Force includes hidden and system files, and -ErrorAction SilentlyContinue skips folders you can't read (Get-ChildItem, Measure-Object).

Get-ChildItem -LiteralPath $env:LOCALAPPDATA -Directory -Force |
  ForEach-Object {
    $bytes = (Get-ChildItem -LiteralPath $_.FullName -Recurse -File -Force -ErrorAction SilentlyContinue |
      Measure-Object -Property Length -Sum).Sum
    [pscustomobject]@{ Folder = $_.Name; GB = [math]::Round($bytes / 1GB, 2) }
  } | Sort-Object GB -Descending | Select-Object -First 15

It takes a minute or more on a big profile. For Roaming, swap $env:LOCALAPPDATA for $env:APPDATA. The result tells you where to look. It is not a list of things to delete.

Step 2: know what you are looking at

The WSL path comes from Microsoft's WSL disk-space page, which also shows how to look up the exact path for your distro (WSL disk space). NuGet's locations and commands are in Microsoft's NuGet docs (NuGet folders), and the npm cache location is in npm's docs (npm cache).

Rules before you delete anything

• Don't delete a whole app folder to "reset" it. You lose its settings, logins and sometimes its data.
• Be extra careful in Roaming. It mostly holds settings, not cache.
• Close the app first. Files in use can block the delete or leave the app half broken.
• Use the proper route when there is one: the app's own clear-cache option, Storage Sense, or the package manager's cache command.
• If you don't recognise a folder, search its name before you touch it. Folders left by apps you uninstalled ages ago are the safest to remove, but make sure the app is really gone.

Where developers lose the most

On a dev machine the biggest entries are usually a WSL distro's virtual disk and tool caches. These guides cover them: Why your WSL2 disk file never shrinks, Where Docker Desktop's disk space goes and How to clear npm, pip and NuGet caches.

Doing it without the command line

SpaceFree measures the developer-related items from this list: WSL2 and Docker virtual disks, package caches, IDE and build tool caches, and temp files. It shows each size and tags every item as safe to delete, rebuildable or not cleanable before anything is removed, and deletions go to the Recycle Bin by default. Download SpaceFree.