Have you ever hit Win + R to quickly jot down a note, only to be greeted by a confusing error saying “Microsoft.UI.Windowing.Core.dll was not found”? You aren’t alone. As Windows 11 evolves, apps like Notepad have transformed from simple executables into modern WinUI 3 applications. While this brings a sleek new look, it can sometimes lead to technical hiccups.
In this article, we’ll explore what Microsoft.UI.Windowing.Core.dll actually is, where it belongs, and why you should never try to move it manually. We will also break down exactly how to fix the error so you can get back to your workflow. Whether you are a tech enthusiast or just want your Notepad back, you’re in the right place!
What Is Microsoft.UI.Windowing.Core.dll?
Microsoft.UI.Windowing.Core.dll is a vital system component used by applications built with the Windows App SDK Runtime. Unlike older files you might be familiar with, this isn’t a standalone file you manage yourself; it is the engine behind the modern look and feel of apps like the new Notepad.
Key Features
- Runtime Dependency: It is part of the Windows App SDK, ensuring modern apps run smoothly on your system.
- Modern UI: It powers features like custom title bars, modern resizing behaviors, and high-DPI scaling.
- System Managed: Windows handles this file automatically—it is not designed to be copied, moved, or manually installed by users.
- Safety: It is a 100% safe, official Microsoft component, provided it is in the correct system folder.
Where Does It Actually Go?
Many users ask, “Where do I put this file?” The short answer is: You don’t.
The file is stored internally inside protected system folders managed by Windows. Specifically, it resides in a locked directory, typically found here: C:\Program Files\WindowsApps
Important Note
Do not download this DLL from third-party websites. Downloading DLL files from random sites is dangerous. They often come bundled with malware or version mismatches that can break your system further. If Windows cannot find the file, it means the runtime is corrupted or Notepad is looking in the wrong place, not that the file needs to be manually pasted.
Why Does This Error Appear?
The issue usually stems from a conflict between the Classic Notepad and the Modern Notepad. When you open Notepad from the Start Menu, it works perfectly. However, using the Run command (Win + R) relies on specific registry paths that may still be pointing to the wrong location.
Classic vs. Modern Notepad Execution
Here are the differences in how Windows handles Notepad, which leads to this error:
| Aspect | Classic Notepad (System32) | Modern Notepad (WinUI 3) |
| Technology | built on older Win32 architecture. | Built using the modern Windows App SDK. |
| Location | Located in C:\Windows\System32. | Located in a hidden WindowsApps folder. |
| Launch Method | Launches directly via executable. | Requires the App SDK Runtime to function. |
| The Problem | Windows sometimes tries to launch the Modern app using Classic methods, causing a “DLL Not Found” error. |
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How to Fix Microsoft.UI.Windowing.Core.dll Errors?
Fixing this issue requires correcting how Windows looks for the app, rather than moving files around. Here are the most effective methods to get Notepad working again.
Method 1: Run System File Checker (Recommended)
This is the standard first step to repair corrupted system components or missing runtime links.
- Press Windows + S and type cmd.
- Right-click Command Prompt and select Run as administrator.
- Type the following command and hit Enter:
sfc /scannow - Wait for the process to finish and restart your PC.
Method 2: Clear the App Paths Registry (Most Effective)
This forces Windows to stop looking for a broken link and use the correct default path.
Using PowerShell:
- Open PowerShell as an Administrator.
- Copy and paste this command:
Remove-Item -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\App Paths\notepad.exe" -Force - Restart your PC.
Method 3: Reset or Reinstall Notepad
If the app itself is glitchy, a quick reset often solves the problem without affecting your documents.
- Go to Settings > Apps > Installed Apps.
- Search for Notepad.
- Click the three dots (…) and select Advanced options.
- Click Repair or Reset.
Frequently Asked Questions
Here is a summary of common questions regarding missing DLL files:
- Is Microsoft.UI.Windowing.Core.dll a virus? No, it is an official file from Microsoft used for modern app interfaces.
- Should I download the file manually? No. Never download DLLs from unofficial sites. Always use Windows Update or SFC commands to restore them.
- Why does Notepad work from the Start Menu but not Run? The Start Menu uses the correct modern shortcut, while the Run command (
notepad.exe) may rely on a broken registry entry (“App Paths”) that needs to be cleared.
Conclusion
To sum up, Microsoft.UI.Windowing.Core.dll is a crucial part of the modern Windows experience, but it is not a file you need to manage manually. The error usually indicates a confusion in the system registry rather than a missing file. Understanding the difference between the packaged app and the classic executable helps clarify why these errors happen. By following the steps above—specifically cleaning the registry path or resetting the app—you can resolve the issue safely. So go ahead, apply these fixes, and get back to using Notepad without those annoying error pop-ups!
