appmanifest_<appid>.acf

Updated: 2026-08-25

One text file per installed game, a few kilobytes each. It is not the game; it is Steam's note to itself that the game is there. Almost every "my library is wrong" problem is a disagreement between this file and the disk.

What it is for

Steam does not look at your drives to decide what is installed. For each game it reads appmanifest_<appid>.acf from the library's steamapps folder, and that file is the claim. No manifest, no installed game — however many gigabytes are sitting in common next to it.

Windows	`<Steam>\steamapps\appmanifest_<appid>.acf`
Linux and Steam Deck	`~/.local/share/Steam/steamapps/appmanifest_<appid>.acf`
A second library	`<library>\steamapps\appmanifest_<appid>.acf`

What is inside

VDF, the same key–value format as libraryfolders.vdf. The fields worth knowing:

appid and name — the game, in a file whose own name only carries the number.
installdir — the folder under steamapps\common. It does not always match the store name.
SizeOnDisk — what Steam reports on the storage screen. It is a recorded figure, not a measurement, which is why that screen can disagree with the actual folder.
buildid and LastUpdated — how Steam decides an update is needed.
StateFlags — the state of the install.
InstalledDepots — which pieces of the game were actually downloaded, language packs and optional content included.

StateFlags

A bit field, and the reason a game can show as installed and still refuse to play. 4 means fully installed and ready. Anything else means Steam considers the install incomplete: an update queued, a download running, or a validation pending. A game stuck at a value other than 4 usually has files in the downloading folder.

What deleting one does

Deleting a manifest frees no space. The file is a few kilobytes. What it does is make Steam forget a game you still have on disk — which then shows as not installed and offers to download again, on top of the copy already there.

That is worth being precise about, because "delete the acf file" is common advice on forums. It is the right fix for exactly one situation: the game is genuinely gone from the disk and Steam still lists it. Then the manifest is the thing lying, and removing it is how you tell Steam the truth.

The reverse case is a ghost install: files present, no manifest. Steam sees nothing, and the gigabytes are invisible on the storage screen.

Rebuilding one

If the files are there but the manifest is not, you do not have to re-download. Start the install and stop it after a second: Steam writes the manifest, finds the files already present, and switches to verifying instead of downloading. Steam has to be closed before any manual edit, or it rewrites the file on exit.

Act on it

Vapor Storage Manager cross-references every manifest against the files on disk and reports both directions of the mismatch — manifests with no files, and files with no manifest. It backs up each one before removing it, and never touches a manifest whose game is really installed.

Download Vapor Storage Manager