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I realize that many times when there is an issue with a game on Steam, it can be solved with "Verify Integrity of Game Cache". But, what exactly does this do?

I tried running Darksiders and it gave me an error of "Missing Executable", so I figured the verify would easily catch that and install the missing files. I was wrong, though, since the validation found no problems with the installation and the game continued to not launch from the same error.

I'm curious as to what exactly the verify option does. I know on some other games I have tried it on, steam will end up downloading some files, but apparently not all files are included in this.

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  • It's likely doing some sort of checksum, comparing it to the values stored on the Steam servers, then determining if something needs to be replaced.
    – Nolonar
    Commented Dec 15, 2013 at 23:18
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    Interesting, I've definitely seen this redownload an exe when I've manually patched the exe so it's checksum would be different. I wonder if the fact that it was completely missing prevented it from redownloading. Seems an odd oversight for Valve to make...
    – Rob
    Commented Dec 17, 2013 at 16:19

3 Answers 3

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It compares the game files you have on installed your computer with those of of the latest version on the steam servers. If its different in any way it replaces or adds on any files.

If I ever have a problem with a game on steam this always the first thing i do.

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  • So why would "Missing Executable" not get downloaded, or even detected, from this process?
    – Batophobia
    Commented Dec 16, 2013 at 15:50
  • Have you tried re-installing the entire game?
    – Bungalo Soldier
    Commented Dec 17, 2013 at 10:08
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    Yes and that worked, but I had to delete it first to get the install option. After that I had to wait for the 10GB game to download and install itself. Seems like if Verify checks against the files I downloaded during installation, then it should have picked up on the executable error.
    – Batophobia
    Commented Dec 17, 2013 at 15:36
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    @Batophobia Sounds like it was missing the proper directory structure, or that a file got corrupted somehow. Verification tools are good for running a simple check to see if your base files are in good order, but no tool is perfect.
    – Zibbobz
    Commented Jul 15, 2014 at 18:17
  • @Zibbobz I understand that, but you'd think the executable would be included in the base files. Also, knowing how this works can be helpful in solving problems where this step does not resolve the issue.
    – Batophobia
    Commented Jul 15, 2014 at 19:06
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The Steam Client conducts a checksum of the *.manifest files for the game. If your local checksum mismatches the checksum on the Steam Servers, the client will download the files that are "corrupted".

In other words, say your game is several word files in a folder. It will go through each file and count all the a's, b's, ..., z's in the files. If the count is mismatched with the Server record, you will be triggered to redownload the errant file(s).

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What happens is that it checks the games has all the proper files (sometimes if you want to mess with maps and stuff might accidentally delete some stuff so it adds all the right files!) This happened when I was trying to make Portal 2 and Stanley pabs together and I deleted some files accidentally. So I clicked the Verify thing and I could play Stanley pabs again!

Hope this helps!

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