Fix the api-ms-win-core-libraryloader-l1-1-1.dll is missing error

Martin Brinkmann
Jan 3, 2018
Updated • Jan 3, 2018

You may get the error message api-ms-win-core-libraryloader-l1-1-1.dll is missing when you try to upgrade a PC running Windows 7 to Windows 10.

The error is not limited to the upgrade from Windows 7 to Windows 10 and the Windows10UpgraderApp.exe. Windows 7 users ran into the error when they tried to run other programs on Windows 7 as well, but the bulk of issues is caused by Microsoft's upgrade tool.

The error is thrown after you run the Windows 10 Update Assistant on the Windows 7 machine. The Update Assistant downloads the Windows 10 installation files fine but throws the error when it starts the installation of the operating system.

The Error Message

api-ms-win-core-libraryloader-l1-1-1.dll missing

The error message reads:

The program can't start because api-ms-win-core-libraryloader-l1-1-1.dll is missing from your computer. Try reinstalling the program to fix this problem.

The description is not that useful. It does highlight that a dll library file is missing on the computer, but gives no indication where users may get it or which program they may need to re-install to add it.

How to fix it

fix issue

The fix is simple thankfully. All you need to do is copy a DLL file from the system32 folder of the Windows 7 installation to the root Windows10Upgrade folder.

  1. Open c:\windows\system32\ using Explorer or another file manager.
  2. Type "wimg" quickly to jump to the right file. Or, browse until you find the file wimgapi.dll this way.
  3. Select wimgapi.dll, right-click on it, and select copy from the context menu.
  4. Open c:\Windows10Update\
  5. Right-click on the folder and select Paste.
  6. Confirm that you want to replace the pasted DLL file with the existing one.
  7. The process may require elevation. Accept the prompt as well.

Restart the upgrade to Windows 10 once you have copied the file wimgapi.dll from the system32 folder to the Windows10Upgrade folder.

The download step is skipped this time as the files are still cached on the local system. You should notice that the installation proceeds as planned at this point. Congratulations, you fixed the error.

Closing Words

The error api-ms-win-core-libraryloader-l1-1-1.dll is missing appears to be a packaging error that Windows 7 users ran into after the release of the Fall Creators Update.

The file api-ms-win-core-libraryloader-l1-1-1.dll that the Windows 10 Upgrade Assistant uses is not a Windows 7 DLL file and is therefore not on machines running Windows 7.

What makes this particularly difficult to troubleshoot is that you cannot get the missing dll file for Windows 7.

Microsoft needs to release an update for the Windows 10 Upgrade App to fix the issue. Users and admins who run into it in the meantime can resolve it with a quick copy and paste action.

Fix the api-ms-win-core-libraryloader-l1-1-1.dll is missing error
Article Name
Fix the api-ms-win-core-libraryloader-l1-1-1.dll is missing error
You may get the error message api-ms-win-core-libraryloader-l1-1-1.dll is missing when you try to upgrade a PC running Windows 7 to Windows 10.
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  1. troubled program said on August 3, 2019 at 9:51 am

    i cant find windows10uprgade or pdate anywhere and my computer is windows 8 but its not bloody working

  2. simran sidhki said on October 31, 2018 at 12:47 pm


  3. Anonymous said on February 27, 2018 at 1:42 pm

    Thank you very much bro, keep it up

  4. Gaby1988 said on February 27, 2018 at 11:28 am

    Thank You !!

  5. Aman said on February 23, 2018 at 5:29 am

    Thanks sir… Started the installation..

  6. Michael said on February 22, 2018 at 7:07 pm

    How do you fix the problem on Win 7 and I didn’t run the 10update

  7. Anonymous said on February 16, 2018 at 3:38 pm

    Your awesome thank you for sharing this information.

  8. mick said on February 10, 2018 at 4:01 am

    now it just keeps failing

  9. Anonymous said on February 5, 2018 at 9:22 pm

    Thanks so much for this! I heard that the fix involved messing around with System32 files and was immediately terrified, but your step-by-step process made it quick and easy.

  10. Anonymous said on February 1, 2018 at 9:24 am

    Great advice,works well


  11. Anonymous said on January 28, 2018 at 2:17 am

    Wow, wild fix for this. THANK YOU

  12. Anonymous said on January 22, 2018 at 9:56 pm

    Thank you… so freaking much.

  13. Gurpreet Singh said on January 20, 2018 at 7:32 pm

    Thanks:) A very simple solution.

  14. Ash said on January 14, 2018 at 9:05 pm

    All was good but when i put c:\Windows10Update\ it says it cant find it?

    1. Anonymous said on February 13, 2018 at 6:01 am

      C:\Windows10Upgrade it may be on some pc’s

  15. Tony said on January 10, 2018 at 2:48 am

    Thank you! I thought upgrading from Windows 7 to Windows 10 would be a nightmare for this evening. This post helped me to correct the error that Windows upgrade was throwing at me.

  16. Anonymous said on January 7, 2018 at 9:09 pm

    Thank You

  17. Rick A. said on January 5, 2018 at 2:51 am

    i ran into this problem on new years eve trying to get my other Laptop from Windows 7 to Windows 10. i found the fix on another site. But i can verify that this will fix the problem.

  18. 4cameraForked said on January 5, 2018 at 1:23 am

    Hey how do I eat horrible nutrition so that I have stents and heart attacks, what’s the best beer to drink and fastest cigarretes to lung cancer and liver failure diabeties and heart failure.

    I was just wondering maybe I could get the BEST advice to my timely end.

    Seriously I want to upgrade my computers too, I mean they need to be FAST instead of having all those decades of pesky family photos or old recorded songs of dead people who worked for years..

    Of course it’s my fault for not educating myself on the proper replacement of failed backup systems and failed recovery and allowance of younger friends to format C every month so that no data really ever exists of your (and I mean “OUR” this time) existance anyway.

    This is for the best, I mean why would you possibly want to remember the HORROR or back stabbing or even attempt to unwind the madness I am ranting on about. It’s a good thing I don’t drink. But it’s a good thing you care even less about your History, or Past or Family. I must upgrade the wallet to bitcoin and computer to a flash disk, website /network in the cloud and ISP/wireless. NOthing wrong with tracking, just look at the stop sign, it needed 4 cameras.

    1. Anonymous said on January 18, 2019 at 3:48 pm

      You need to switch to decaf.

    2. Anonymous said on January 5, 2018 at 4:14 pm


      Are you alright?

  19. Richard said on January 4, 2018 at 7:20 pm

    all went well up to the final step of windows 10 upgrade, it locked at 99% in the installing windows phase. i left it like this overnight. I did check the Task Manager and it said the upgrade is running….12 hours at 99% and no change….

  20. MazterGee said on January 4, 2018 at 1:47 pm

    Good Fix, thanks for sharing.

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