Where did my C: drive space go

Updated: 2026-08-25

Moving your library to a second drive moves the games. It does not move the caches, the prefixes, the launcher data or the saves — and those are what quietly fill the system drive over a couple of years.

Why moving the library did not help

A Steam library holds game installs. Nearly everything else a launcher writes is keyed to your Windows user profile or to the client's own install, both of which are on C: — and none of it moves when you add a library elsewhere.

What is on C: no matter where your games are

GPU shader caches, all vendors	`%LOCALAPPDATA%\NVIDIA, \AMD, \Intel, \D3DSCache`
Steam client caches	`<Steam>\appcache and <Steam>\steamapps\depotcache`
Steam Cloud saves and per-game config	`<Steam>\userdata`
Game saves and settings	`%USERPROFILE%\Documents\My Games, %APPDATA%, %LOCALAPPDATA%`
Epic, EA, Ubisoft, GOG launcher data	`%LOCALAPPDATA% and %PROGRAMDATA%`
Mod manager downloads and profiles	`%LOCALAPPDATA%\ModOrganizer, r2modman, Vortex, CurseForge`

The shader caches are usually the largest single item and the most surprising, because nothing in any launcher shows them to you. What they are and why they are safe to clear.

Work through it in order

Shader caches. Largest, safest, rebuilds itself. Start here.
Steam client caches — appcache and depotcache. Both rebuild; how to clear them properly.
Leftovers from games you uninstalled, which are not only on the drive the game was on. Where they hide.
Mod manager downloads. Mod Organizer 2, r2modman, Vortex and CurseForge each keep every archive they ever downloaded, and none of them prune.
Abandoned downloads — the downloading folder — which can hold tens of gigabytes for a game that no longer exists.

What not to clear

<Steam>\userdata is Steam Cloud's local side and the per-game settings for your account. It is often a few gigabytes and it looks exactly like a cache. It is not one.

Likewise everything under Documents, %APPDATA% and %LOCALAPPDATA% that belongs to a game rather than a launcher: those are saves and settings, and Steam Cloud does not cover every game.

Stopping it coming back

Point new installs at the second drive by making it the default library: Steam → Settings → Storage, select the drive, set as default.
NVIDIA's shader cache has a size limit in the Control Panel, under Manage 3D Settings → Shader Cache Size. The default is not generous so much as unbounded on some driver versions.
Mod managers almost all let you move their download folder in their own settings. Doing it once saves the largest recurring item on this list.

Act on it

Vapor Storage Manager scans every drive at once rather than one library at a time, and groups what it finds by launcher and by category, with the size of each. It is the same list as above, filled in with your actual numbers instead of folder names to go looking for.

Download Vapor Storage Manager