How does Steam uninstall games so damn quickly?

[DJ Satomi]

Even a huge game like Doom or GTA 5 is gone practically instantly after you hit the button. Uninstalling games outside of Steam takes way, way longer and I'm really curious how Steam does this.

[ShelLuser]

This is just a (somewhat educated) guess but one part of it seems to be that Steam simply removes the game but doesn't bother itself with any optional components. You know: some games also install other things like a new ActiveX library and such.

Well.. during de-install of a game many also try to uninstall those extra components while also making sure that they're not being used by other programs anymore. That in itself takes extra time, and it's something Steam doesn't do.

I wouldn't even be surprised if Steam doesn't even really uninstall but simply deletes the game directory from its library and then deregisters the software from the OS.

[[R] Nerva]

When Steam uninstalls, it only removes library entries, desktop links & the game's primary executable immediately.

Everything else is consigned to a background process to finish the uninstallation. As a result, it only seems that the process is instantaneous, when in reality it's still going on in the background, at a low priority so as to interfere with your use of the system as little as possible. This is easiest to notice on lower-end machines that are running software that's at their limit, as the ongoing uninstallation still uses some resources.

Some games never actually get fully uninstalled. Their entry in your library is disabled and any desktop links are removed, but the rest of the game's files remain in the Steam directory, taking up space. Steam may even leave the appmanifest in place, so that when the game is reinstalled, the reinstallation is extremely brief as it only has to download a few files and re-use the existing ones left behind from the previous installation. Dungeon Fighter Online does this.

[Satoru]

So basically this is how it 'generally' works

If you're instaling a game outside of steam you are by and large, using either a microsoft MSI installer or wise/installshield. Basically these are 'databases' that run through various tasks to install and reinstall something. So to uninstall the game, it reads the database, checks for what it needs to do, goes and finds a bunch of files, deletes each file, does some more cleanup in the registry, etc.

For steam it knows where games are installed and that nothing is going to be underneath them because of steam is set up so it does basically this

rm -rf <game directory>

which basically takes no time

[Start_Running]

It works so quickly because of how steam compartmentalizes the games. Pretty much each install is contained entirely (with the exception of config and save directories sometimes) So when you uninstall a game in steam, its basically just deleting the files in the game's directory. No hunting down secondary components, no tracking down registry entries, etc, its all self contained.