mrt100.dll is a Microsoft file associated with the .NET Native runtime used by some compiled Windows and Microsoft Store applications. If mrt100.dll is missing, not found, or could not be loaded, repair the application and its Windows dependencies rather than downloading a replacement DLL.
The correct fix depends on which application displays the error. A Store or UWP app usually needs package repair or reinstalling. A damaged Windows component needs Windows Update, DISM, and System File Checker. A desktop program may need repair or reinstallation from its official installer.
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First, identify what is failing
Before changing system files, record the complete error and the program name. Common wording includes:
- “mrt100.dll is missing”
- “mrt100.dll was not found”
- “The code execution cannot proceed because mrt100.dll was not found”
- “This application failed to start because mrt100.dll was not found”
- “mrt100.dll file could not be loaded”
- “Cannot find mrt100.dll”
The exact message varies by application, Windows version, and process architecture.
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Ask these questions:
- Which program or game fails?
- Did you install it through Microsoft Store, MSIX/AppX, or a desktop installer?
- Did the problem begin after Windows Update, an app update, cleanup software, antivirus activity, disk trouble, or an interrupted installation?
- Does the error affect one application or several Store apps?
- Does Windows Update work normally?
- Is the affected program 32-bit, 64-bit, ARM64, or packaged for multiple architectures?
This distinction prevents a common mistake: treating an application package problem as proof that a single system DLL must be copied manually.
What mrt100.dll does
Microsoft documents mrt100.dll as a library related to the .NET Native runtime. It can improve the performance of mrt100_app.dll, which is normally included with the compiled application. When present, mrt100.dll is loaded from the local computer’s System32 directory according to Microsoft’s .NET Native documentation.
These files are related but not interchangeable:
mrt100.dllis a Windows-side .NET Native library.mrt100_app.dllis an app-local .NET Native runtime library.Microsoft.NET.Native.Runtimepackages are packaged Store-app dependencies.msvcr140_app.dllis a packaged C runtime dependency.msvcr100.dllbelongs to the Visual C++ 2010 runtime.
The absence of mrt100.dll does not necessarily stop mrt100_app.dll from functioning in Microsoft’s documented .NET Native design. An app can still fail because its package registration, runtime dependency, or Windows component store is damaged.
Do not expect the modern .NET Desktop Runtime, .NET Framework, or Visual C++ Redistributable to automatically restore this file. They are different products.
Fix 1: Repair or reinstall the affected Store app
Time needed: 5–15 minutes
Use this first when the error appears in a Microsoft Store, UWP, MSIX, or AppX application.
Repair the app
- Press Windows + I to open Settings.
- Select Apps.
- Select Installed apps.
- Find the application that displays the
mrt100.dllerror. - Select the three-dot menu beside it.
- Choose Advanced options.
- Select Repair.
- Start the application again.
Repair preserves the app’s data while replacing or correcting some application files and registration data.
If the error remains:
- Return to the same Advanced options page.
- Select Reset.
- Confirm the reset.
- Launch the application again.
Reset can remove the app’s locally stored data, so use it only after considering whether the application stores unsynchronized settings or saves locally.
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- Open Settings.
- Select Windows Update.
- Select Check for updates.
- Install all available updates.
- Restart Windows, even if it does not immediately request a restart.
- Open Microsoft Store.
- Select Library.
- Select Get updates.
- Allow the Store to update the affected app and any related packages.
Store applications may depend on versioned packages such as Microsoft.NET.Native.Runtime.1.7 or Microsoft.NET.Native.Runtime.2.2. These packages are separate from the system-side mrt100.dll, and the required architecture and minimum version are defined by the application package.
Reinstall the Store app
If repair and reset do not help:
- Open Settings > Apps > Installed apps.
- Select the affected application.
- Choose Uninstall.
- Restart Windows.
- Open Microsoft Store.
- Search for the application.
- Select Get or Install.
- Launch it after installation completes.
Reinstalling through Microsoft Store is safer than downloading a runtime package from an unofficial source because the Store supplies the application and its supported package dependencies together.
Fix 2: Repair Windows components with DISM and SFC
Time needed: 15–45 minutes
Use this when mrt100.dll is missing from its expected protected Windows location, several applications fail, or the problem began after an interrupted update, disk error, or system cleanup.
First install pending updates and restart. Then:
- Open the Start menu.
- Type Command Prompt.
- Right-click Command Prompt.
- Select Run as administrator.
- Approve the User Account Control prompt.
- Run this command:
DISM.exe /Online /Cleanup-Image /RestoreHealth
Wait for DISM to finish. It may appear to pause for a while. Do not close the window during the repair.
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When DISM completes, run:
sfc /scannow
Microsoft recommends running DISM before SFC because DISM can repair the component source that SFC uses. The commands and result meanings are covered in Microsoft’s guide to repairing missing or corrupted system files.
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Restart Windows after SFC finishes, then test the application.
How to read the result
- “Windows Resource Protection did not find any integrity violations” means SFC found no protected system-file corruption.
- “Windows Resource Protection found corrupt files and successfully repaired them” means restart and test the app.
- SFC found corruption but could not repair some files means run Windows Update again, restart, and repeat the DISM and SFC sequence.
- DISM could not obtain repair files means use a matching Windows installation source according to Microsoft servicing guidance. Do not replace the source with a downloaded DLL.
Repeatedly running SFC and DISM by hand can make it difficult to see what changed. Outbyte PC Repair can scan for system issues and show what needs attention, while repair actions are provided by the full version. It is optional, and Windows servicing remains the direct fix for a damaged component.
Fix 3: Repair or reinstall a desktop application
Time needed: 10–30 minutes
If only one traditional desktop program or game fails, the application installation is the stronger suspect.
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- Open Settings with Windows + I.
- Select Apps > Installed apps.
- Find the affected program.
- Open its three-dot menu.
- Select Advanced options, if available.
- Choose Repair.
- Test the program.
Some desktop programs instead use Control Panel:
- Open the Start menu.
- Type Control Panel and open it.
- Select Programs > Programs and Features.
- Right-click the affected program.
- Select Repair or Change.
- Follow the installer’s instructions.
- Restart Windows if requested.
For a game, open its official launcher and use its Verify, Repair, or Verify integrity of game files command. The wording differs between launchers. Do not delete the game directory unless the publisher’s instructions specifically require it.
Reinstall from the official source
If repair fails:
- Back up settings, saves, or project files if the application stores them locally.
- Uninstall the affected program from Settings > Apps > Installed apps or Control Panel.
- Restart Windows.
- Download the current installer from the application’s publisher, or reinstall through Microsoft Store.
- Install the program again.
- Start it before restoring optional modifications or third-party plug-ins.
A clean reinstall restores the application’s own files and dependency declarations. It is the definitive remedy when the program’s installation is incomplete or damaged.
Fix 4: Check antivirus quarantine safely
Time needed: 5–20 minutes
If the error began immediately after a security scan or cleanup operation:
- Open your security software.
- Open Protection history, Quarantine, or the equivalent section.
- Search for
mrt100.dlland the affected application. - Do not restore the file solely because its filename looks correct.
- Check that it is located in the expected protected Windows directory.
- Open the file’s Properties and inspect Digital Signatures.
- Restore it only when the signature identifies Microsoft and the detection has been confirmed as a false positive.
- Run an updated Microsoft Defender scan afterward.
If the file is unsigned, stored in a temporary directory, or associated with suspicious behavior, leave it quarantined and scan the system. Windows repair or reinstalling the application is safer than manually restoring an unverified copy.
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Fix 5: Check architecture and Windows paths
Time needed: 5–10 minutes
On 64-bit Windows, System32 is not simply a label meaning “64-bit files,” and SysWOW64 is not evidence that a file is broken. Windows uses filesystem redirection for 32-bit processes. The correct library depends on the Windows build and the process requesting it.
To inspect the file without replacing it:
- Open File Explorer.
- Browse to
C:WindowsSystem32. - Search for
mrt100.dll. - Right-click the file and select Properties.
- Check the Details and Digital Signatures tabs.
- Note the path, file version, and signer.
Do not use a historical file size or version as a universal target. Microsoft’s older Windows 8.1 update records list separate x86 and x64 entries, but those values do not establish the correct version for every Windows 10 or Windows 11 build.
If the affected program is 32-bit, do not automatically copy a file into SysWOW64. If it is 64-bit, do not automatically copy one into System32. Let Windows servicing and the application installer select the correct architecture.
Fix 6: Investigate drivers only when the failing app belongs to a driver suite
Time needed: 10–30 minutes
mrt100.dll is not a driver file. Do not install unrelated device drivers as a general DLL repair. Driver checks make sense only when the failing program is part of a graphics, audio, printer, scanner, chipset, or other hardware vendor package and the error began after a driver update.
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To check a device:
- Right-click the Start button.
- Select Device Manager.
- Expand the category for the relevant hardware.
- Right-click the device.
- Select Properties.
- Open the Driver tab.
- Note the provider and version.
- Use Update Driver or install the current package from the hardware manufacturer.
- Restart Windows and test the vendor application.
Do not replace a working driver merely because mrt100.dll appears in an error. Outbyte Driver Updater can scan for outdated drivers and identify what needs attention, while driver installation is handled by the full version. It is optional; for a program-specific failure, repairing or reinstalling that program remains the definitive fix.
Fix 7: Test another Windows profile and consider recovery
Time needed: 15 minutes to several hours
If the app fails only in one Windows account, its per-user registration or profile data may be damaged.
Create a temporary local account:
- Open Settings.
- Select Accounts.
- Select Other users.
- Choose Add account.
- Follow the prompts to create a local test account.
- Sign in to that account.
- Test the affected application.
If it works there, repair or reinstall the app for the original account and migrate only necessary user data.
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If the error affects every account and Windows repair does not help, consider System Restore to a point before the problem began. If no suitable restore point exists, an in-place Windows repair installation may restore system components while preserving applications and personal files, depending on the installation path and Windows configuration.
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Why downloading mrt100.dll is unsafe
Avoid standalone DLL download pages, “DLL fixer” programs, and instructions that tell you to copy an unknown file into System32 or the application folder. A downloaded DLL can have the wrong architecture, version, signature, or dependency chain. It can also introduce malware, overwrite a protected Windows file, or hide the real problem in the Store package or application installation.
The safe sources are:
- Windows Update and Windows component servicing
- Microsoft Store
- The affected program’s official publisher installer
- The hardware manufacturer’s official driver package when a related vendor application is involved
Why regsvr32 usually does not help
regsvr32 is a registration utility, not a general DLL installer. It works with libraries that expose the registration entry point expected by the utility, commonly DllRegisterServer. There is no evidence that ordinary mrt100.dll repair requires registration.
Do not run:
regsvr32 mrt100.dll
as a routine fix. If it produces a registration error, that does not prove the file is missing or defective. Use Windows servicing or repair the application instead.
Likely causes and matching fixes
- One Store app fails: repair, reset, update, or reinstall that app.
- Several Store apps fail: update Windows and Store packages, then run DISM and SFC.
- One desktop program fails: repair or reinstall it from the official source.
- The problem follows antivirus activity: inspect quarantine and verify the Microsoft signature.
- The issue follows an update or cleanup task: run Windows repair commands and consider System Restore.
- The app fails only in one profile: test a new account and repair per-user registration.
- The program is old: obtain a current version from its publisher rather than forcing an old DLL.
FAQ
Is mrt100.dll a Windows file?
It is a Microsoft file associated with the .NET Native runtime, and Windows may load it from System32. The application that reports the error is still important because Store packages and app-local runtime files can fail independently.
Is mrt100.dll the same as mrt100_app.dll?
No. mrt100_app.dll is an app-local .NET Native runtime library. mrt100.dll is the related system-side library documented by Microsoft.
Should I install .NET Framework or Visual C++ Redistributable?
Not automatically. Those are different runtimes and are not a guaranteed repair for mrt100.dll.
Should I copy the file into System32 or SysWOW64?
No. The correct path and architecture depend on Windows and the requesting process. Use Windows Update, DISM, SFC, Microsoft Store, or the application installer.
Does the file need registration?
Normally, no. regsvr32 is generally irrelevant to this runtime library.
What if the file exists but the app still fails?
Repair or reinstall the affected app, update Microsoft Store packages, run DISM and SFC, and check whether the required Microsoft.NET.Native.Runtime package is installed through supported Windows and Store channels. A present system DLL does not prove that the app’s package dependencies are healthy.
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