libraryfolders.vdf

Updated: 2026-08-25

What it does

Steam does not scan your drives for games. It reads a list, and this is the list: every library folder it knows about, and for each one, which app ids are installed there and roughly how large they are.

That makes it a single point of failure in a useful way — one wrong path and a whole library disappears from the client, while every byte of it is still on the disk.

Where it lives

What is inside

VDF is Valve's own key–value format: quoted keys, quoted values, braces for nesting. The top level holds one block per library, and each block carries a path, some bookkeeping, and an apps block listing the app ids installed there against their size in bytes.

How it breaks

• A drive letter changes, so path points somewhere that no longer exists and the library is dropped.
• An external drive is disconnected. This is indistinguishable from the drive being gone for good, which is why nothing should purge entries automatically.
• A game is removed by hand outside Steam, leaving an apps entry for files that are not there — the game keeps counting toward Steam's storage figures. See uninstalled games still taking up space.
• The file is truncated by a crash mid-write, and then every library is gone at once.

Editing it

Close Steam first. It holds this file open and rewrites it on exit, so an edit made while the client is running is usually overwritten the moment you quit — which looks exactly like the edit not working.

Copy it somewhere safe before touching it. It is a few kilobytes and it is the only record of where everything is.

Most problems do not need an edit at all: Steam → Settings → Storage can add a library folder back, and re-adding the correct path is enough to make a library reappear with its games intact.