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How To Fix The api-ms-win-core-libraryloader-l1-1-1.dll Is Missing Error During Windows 10 Upgrade

Windows 10 has a never ending slew of bugs but they’re rare enough to not effect too many users. That doesn’t mean they’re not a problem. In fact, the more rare a bug is, the harder it is to resolve and Microsoft is less likely to fix it. One bug that users who are still on Windows 7, trying to upgrade to Windows 10 via the WIndows 10 Upgrade app are seeing is the “api-ms-win-core-libraryloader-l1-1-1.dll Is Missing Error”. This is a fairly recent bug that appears to have surfaced after the last major build of Windows 10, the Fall Creators Update was released. Here’s how to resolve it.

The Error

When upgrading from Windows 7 to Windows 10, the upgrade fails and you get the “api-ms-win-core-libraryloader-l1-1-1.dll Is Missing” error. The error is basically telling you a DLL file is missing and without it, the upgrade cannot proceed. It doesn’t tell you where you can download said DLL file.

The Fix

The fix for the “api-ms-win-core-libraryloader-l1-1-1.dll Is Missing” error comes by replacing the DLL file on the following location;


with the DLL file found in the directory given below;


Once you’ve replaced the file, run the upgrade again and this time, it ought to work. This error only appears if you’re upgrading from Windows 7 to Windows 10. If you’re doing a clean install of Windows 10, you won’t see it.

It seems that when packaging the latest updater, Microsoft accidentally had it look for the wrong file. The DLL file that’s missing isn’t supposed to be on your Window 7 machine to begin with. The real fix is probably going to have to come from Microsoft whereby they have the update app look for the correct DLL file. This could take awhile because although the fix is simple enough, it will require a change to the Windows 10 update app which Microsoft is unlikely to make unless there is a major new build that has been released.

The problem has been documented on Microsoft’s TechNet forum and that’s where the viable solution comes from.

Clean Installs Are Better

We should also mention that this is hardly the only problem with Windows 10, and the upgrade process. In fact, if it’s possible you should try doing a clean install of Windows 10 instead of an upgrade. Most errors that users see on Windows 10 are on machines that were upgraded from 7/8/8.1 to Windows 10. The upgrade process is not all that smooth and ends up breaking quite a few things. In fact, users who upgrade from one build of Windows 10 to the next encounter problems too. A clean install is the best way to avoid bugs and broken features.


  1. Thanks mate, Your fix worked like a treat. I loved the clear way you described the problem and the fix. It gave me confidence to trust you. Both my Win 7 computers encountered the problem.

  2. this solustion worked for me! i have lost 2 days to fix this problem, even in Microsoft official website you couldnt find right solution. thank you very much.

  3. after I replaced the ddl the permission page to start is so huge I can’t click accept, it’s off screen and I can’t scroll over to it
    I rebooted and got it before it went huge

  4. Thank you so much! It works for me too! I tried even to reinstall Win 7!… What a shame on MS! Their haste makes so much waste of time for other people!..

  5. This post also helped from tearing my hair out. It’s ridiculous that a huge company such as Microsoft has untested app distributed to users.
    The windows 10 upgrade app is the one who downloaded this wimgapi.dll, yet it rejects it.

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