Let's say I bought a game on retail or another digital, non-Steam download and installed it on my hard drive. I buy the same game (or a minor variant of it, say the GOTY edition) on Steam. It should be possible to use the existing installation to avoid the generally large downloads. This is very useful, as it saves both bandwidth and time.

Previously, as far as I understood, Steam downloaded the game files directly to steam\steamapps\common\<game_name>. Since this folder would be created on starting the download, pausing and closing Steam, copying the game files to this folder, and then validating the game files would make Steam absorb as much as possible and just download the missing files.

Currently, Steam downloads the files to steam\steamapps\downloading\<game_id> and then moves them over to the aforementioned folder once the download finishes. So first of all, what the final folder would be is not clear. So what would be the correct way of doing the same thing, that is, making Steam use as much of the existing files as possible? Should the files be copied to downloading\*\, or should I figure out the actual folder (say via googling) and copy the files to steamapps\common\*\?

More specifically, I had a retail copy of Arkham City installed, and I just bought the GOTY version on Steam. Now I tried both of the above things, in either case, the validating does not seem to do anything. Assuming I have the correct folder name, steamapps\common\Batman Arkham City GOTY, according to this, if I copy the files there, Steam seems to just continue with its 17GB download. If I copy it to steamapps\downloading\200260, then the download keeps stopping every few seconds with "Disk Write Error" after modifying 1 or 2 files, and I have to keep hitting resume.


6 Answers 6


I think the following is the correct way to currently do what I wanted:

  1. Ensure that Steam thinks the game is not installed. Close Steam just to be sure.
  2. Copy the game files to SteamApps\common\<game_name>, where <game_name> is to be found out via googling/equivalent. In my specific instance, this was Batman Arkham City GOTY.
  3. Launch Steam and install the game. The installation will go through a "Discovering existing files for _" stage.
  4. Watch and wait as it downloads only the missing parts.

I still have to download 9.8 GB though (instead of 17) in my specific case.

  • 1
    are you sure it actually downloading only 9.8GB/17GB instead of 9.8 then uncompressing it to 17GB? When you actually get it installed, did it keep your game saves? how big is the resulting folder that holds the steam install?
    – Colin D
    Commented Jan 8, 2013 at 19:44
  • @ColinD If I started the download from scratch, it wanted to download 17 GB, and I know it has downloaded only 9.8 GB using this method. I also noticed that after the "discovering" stage was over, the common\* folder was reduced to around 7 GB, presumably by removing the files that don't match. The final folder size is 18.6 GB. It didn't keep the saves, probably since the Steam saves are kept somewhat differently than the retail version (I didn't need it to anyway, since I was did a fresh playthrough for the Steam achievements).
    – ronno
    Commented Jan 8, 2013 at 19:50
  • I'm trying to do this (with Thief), but Steam doesn't "see" the files. Is there an actual "Discovering existing files" stage ?
    – Manu
    Commented Mar 7, 2014 at 16:53
  • @Manu There was, at least when this answer was written. Are you sure you are using the correct directory name (<game_name> in the answer)?
    – ronno
    Commented Mar 7, 2014 at 16:58
  • That may be it, I thought it was "ThiefGame" based on what I saw in the Downloading folder, but it may be simply "Thief". I'll try that.
    – Manu
    Commented Mar 7, 2014 at 17:52

Actually you can bind a steam app folder simply from the steam gui!

view -> settings -> download -> steam library folder

and then choose your shared steam folder. Also now steam let you choose where download games; i hove NOT tested cross-gaming (using the same folder on windows and linux), but just relinked my folder (somehow steam lost track of my external HDD) and everythings work fine.

Tested having game in different HDD/partition and works fine. If you Start up steam without external HDD, a reboot of steam is needed to let it "see" the folder


Go to Steam -> Setting -> Download -> Steam Library Folder -> Add your old folder

Ideal folder structure that I added:

Main Folder
- SteamApps
  - common
    - DOTA 2 beta
    - DOTA2 test
  - downloading
  - temp
  - appmanifest_xxx
- steam.dll
- steam2.dll
  • This will not work if you only have the steamapps folder backed up. Commented Jan 6, 2021 at 5:30

Issue solved:

Hope this helps you guys.

  1. Go to View > Settings > Downloads
  2. On STEAM LIBRARY FOLDERS add the folder on the unit where you want to have your games (must be empty, Steam will prompt if not) and close.
  3. Go to that folder and you should have the following structure:
    • new_folder>
      • SteamApps> <- create this folder! (no ">"...)
      • common> <--- create this folder! (where games go)
      • downloading> <--- won't exist unless are downloading something
      • appmanifest_xxx.acf <--- copy all the appmanifest_xxx.acf files you have
  4. Copy all the games folders from your old .../common/ folder to the new location (into the new .../common/ folder you just created).

At this point games will not work. This will make your Steam recognize your games...

  1. Copy all appmanifest_xxx.acf files from from the old .../steamapps/ folder into the new one. THIS IS WHAT MAKES STEAM SEE THE GAMES. For each game there is one manifest.

  2. Play the game.



  • 1
    That's very nicely explained and detailed, but I'm not sure this actually answers the question being asked. This seems to ask about moving the files from one Steam installation to another, while the question is about moving the files from a non-Steam installation to Steam.
    – DJ Pirtu
    Commented Mar 26, 2015 at 8:01
  • I came here from Google, this resolved my issue so +1. One thing i'd note is to open each manifest with a text editor and check which game you're trying to add and move that one.
    – Edward
    Commented Dec 24, 2017 at 2:56
  • Nice, the part I was missing was moving the manifest files. Once I copied these to the new location, Steam recognized all of the games immediately. Cheers! Commented Dec 2, 2020 at 5:28

This solution should work if the game is displaying in the library folder in Steam with the words 'update required' written next to it but the game won't recognize the existing game files on the hard drive.

-Pay close attention to these steps!!!-

  1. -Important- First go to your games folder either in Steam\SteamApps\Common or whatever folder you've already copied the game to and make a copy of the game to a different destination on the hard drive other than in the Steam folder or copy it to a external hard drive as a back up. The next step will delete the game folder in the Steam\SteamApps\Common directory. So this is why this is important.

  2. Go to your Steam library and right click on the game that is causing the issue and then click "delete local content". This will delete the game file from the Steam library and from the Steam directory on the hard drive.

  3. Now copy the games folder back into the common folder located in Steam\SteamApps\Common from the location we had copied it to before in step #1

  4. Finally open Steam, the game title should now be grey-ed out in the Steam library and when you right click on it, it should say "install game..." click on install game and choose the games directory for installation (usually the the default one) is the one to choose, click next, Agree... now it should say discovering existing files... (this is a good thing) and click finish. Now it should work.

If so congratulations! if not idfk what will work but this seemed to work for me. If it did work for you please leave a comment so i can be sure this is a solution that others can use.

  • Yes this worked for me did not have to download a 40 gig game all over again over a 1 Mb/s internet speed.Just follow the instructions to a tee.
    – user88846
    Commented Oct 11, 2014 at 10:59
  • Works perfectly! I had started an update and the accepted answer didn't work. Thanks! Commented Jul 30, 2017 at 8:59

Tried everything and this worked:

Step 1: go to settings/backup or restore | game on a computer that has the game ---> choose game to backup and where to back it up to. Step 2: go to settings/backup or restore game ---> choose file to restore on the computer that you want it on. Click install and you are all ready to go.

If you cant understand what I have said just watch the youtube video

Hope it helps

  • That video is at least slightly NSFW, due to the background. Any chance you can use a different video?
    – Frank
    Commented Mar 27, 2015 at 16:33

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