mrt100_app.dll Is Missing: Rebuild the App That Needs It

mrt100_app.dll is a Microsoft .NET Native runtime component used by some compiled Microsoft Store and UWP apps. If Windows says it is missing or cannot be loaded, repair the affected app or its package dependencies rather than downloading a loose DLL.

The safest first fix is to update Windows and Microsoft Store, then repair or reinstall the app that shows the error. Do not copy mrt100_app.dll into System32, SysWOW64, or an app folder.

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Fix 1: Restart, update Windows, and update Store apps

Time needed: 5–15 minutes

A failed app update or incomplete framework installation can leave a Store app without a required runtime file.

1. Restart Windows.
2. Open Start > Settings > Windows Update.
3. Select Check for updates.
4. Install all available updates and restart if Windows asks.
5. Open Microsoft Store.
6. Select Library.
7. Select Get updates.
8. Wait for the affected app and its framework packages to finish updating.

Try opening the app from the Start menu afterward. If it opens normally, the missing dependency was likely restored during the update.

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Microsoft documents the update and Store repair process in its Microsoft Store app troubleshooting guidance.

Fix 2: Repair the affected Store app

Time needed: 2–5 minutes

Repair is the best next step when only one app reports mrt100_app.dll. It reinstalls or refreshes app data without immediately removing the app.

1. Open Start > Settings.
2. Select Apps > Installed apps.
3. Find the app that displays the error.
4. Select the three-dot menu beside it.
5. Select Advanced options.
6. Under Reset, select Repair.
7. Launch the app from Start.

If the error remains, return to the same screen and select Reset. Reset can remove the app’s local settings, saved data, or sign-in state, so use it only after Repair fails.

If the app does not appear under Installed apps, or Advanced options has no Repair button, continue with a reinstall.

See Microsoft’s repair and reset instructions for Windows apps.

Fix 3: Reinstall the app from Microsoft Store

Time needed: 5–15 minutes

A broken or incomplete package is the most likely cause when one Store app reports a missing runtime file.

1. Open Microsoft Store.
2. Select Library.
3. Locate the affected app.
4. Select the download or install button.
5. If the app is already installed, uninstall it first from Start > Settings > Apps > Installed apps.
6. Restart Windows after uninstalling.
7. Return to Microsoft Store > Library and install the app again.
8. Start it from the Start menu, not from a copied executable.

Reinstalling through Store restores the app’s package registration, permissions, architecture-specific files, and declared framework dependencies. It is more reliable than replacing one DLL manually.

If the app is unavailable in Store, obtain it only through the publisher’s official installation channel. Copying a WindowsApps folder from another computer normally does not preserve the registration and dependencies that the app requires.

Why the .NET Native packages matter

mrt100_app.dll belongs to the .NET Native runtime used by native-compiled UWP applications. It is normally included in the app package or supplied through a framework package, rather than installed as a general-purpose Windows system DLL.

The related framework packages are commonly named:

• Microsoft.NET.Native.Runtime.2.2
• Microsoft.NET.Native.Framework.2.2

Their package versions can vary between Windows and app releases. The required architecture can also differ between x86, x64, and ARM64 systems. A file from a different package version or architecture is not a safe substitute.

UWP manifests declare these framework dependencies. If a dependency is missing or cannot be resolved, deployment or app startup can fail. Microsoft’s documentation explains UWP package dependencies and the role of the .NET Native runtime.

Fix 4: Check Windows Security quarantine

Time needed: 3–10 minutes

Antivirus software can quarantine a package file after an update or after a detection changes. Do not immediately restore the file or download a replacement.

1. Open Start and search for Windows Security.
2. Select Virus & threat protection.
3. Select Protection history.
4. Look for an event involving the affected app, its package, or mrt100_app.dll.
5. Review the detection name and file path.
6. If you believe it is a false positive, confirm that the app came from Microsoft Store or another legitimate publisher source.
7. Follow your organization’s or security software’s review process before allowing or restoring the file.
8. Reinstall the app after resolving the detection.

If Defender repeatedly removes the file, investigate the detection instead of repeatedly restoring DLL copies. Microsoft’s quarantine restoration guidance explains the risks and procedure.

Fix 5: Repair Windows components with DISM and SFC

Time needed: 15–30 minutes

Use this step when several Microsoft Store apps fail, Windows updates are failing, or Store packages appear damaged system-wide. DISM and SFC are less likely to repair one app’s package than an app reinstall.

1. Open Start.
2. Type Command Prompt.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Run:

DISM.exe /Online /Cleanup-Image /RestoreHealth

1. Wait for DISM to finish.
2. Run:

sfc /scannow

1. Restart Windows.
2. Run Settings > Windows Update > Check for updates again.
3. Update or reinstall the affected Store app.

DISM repairs the Windows image, while SFC checks protected Windows system files. A successful SFC scan does not prove that an app package containing mrt100_app.dll is intact.

When manually repeating DISM and SFC makes it difficult to identify what changed, Outbyte PC Repair can scan for reported Windows problems and identify repair areas; its full version performs the repair. It is optional, and reinstalling the affected Store app remains the definitive fix for a broken app package.

Microsoft’s command guidance is available in its documentation for repairing Windows images and update corruption.

Fix 6: Confirm the app architecture and package identity

Time needed: 5–15 minutes

Windows Store apps may use x86, x64, or ARM64 package components. Even on 64-bit Windows, an app may require an x86 dependency. Do not replace an x86 file with an x64 file, or use an ARM64 file on an x64 installation.

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Use the official Store package or the app’s official installer so Windows selects the correct architecture. Avoid extracting a DLL from another PC, another Windows installation, or an unrelated app.

Also avoid launching an executable directly from:

C:Program FilesWindowsApps

Store applications depend on package registration, manifests, permissions, and framework dependencies. Running an .exe directly is not equivalent to launching the registered app from Start. If the app opens from Start but fails from a copied executable or third-party launcher, repair the launcher or use the app’s normal shortcut.

Microsoft’s MSIX dependency guidance describes architecture-specific package dependencies.

Fix 7: Update drivers only when the app has broader graphics problems

Time needed: 10–20 minutes

A driver update is not the normal solution for a missing mrt100_app.dll. Consider it only if the same app also crashes with display errors, rendering problems, or problems that began after a graphics driver change.

To check manually:

1. Right-click Start.
2. Select Device Manager.
3. Expand Display adapters.
4. Right-click the graphics device.
5. Select Update driver.
6. Select Search automatically for drivers.
7. Restart Windows if a driver is installed.

When checking many devices manually means guessing which driver is stale, Outbyte Driver Updater can scan and identify driver updates; its full version installs them. It is optional, and it does not replace repairing or reinstalling the Store app that owns the missing dependency.

Do not use Windows Features to enable .NET Framework as a response to this specific error. .NET Native app dependencies are not the same thing as enabling legacy .NET Framework components.

Do not use regsvr32 for this file

regsvr32 registers DLLs that provide registration entry points such as DllRegisterServer. It is not a general missing-DLL repair command.

mrt100_app.dll is a packaged runtime dependency, not a standalone ActiveX or COM component that should normally be registered. Running a command such as this is therefore not an appropriate fix:

regsvr32 mrt100_app.dll

It may produce an entry-point error and does not restore the app’s package registration or framework dependency graph. Microsoft’s regsvr32 documentation explains its intended purpose.

If Microsoft Store will not open

Time needed: 15–30 minutes

If Store itself is broken, start with:

1. Restart Windows.
2. Install pending updates from Settings > Windows Update.
3. Run DISM and SFC using the commands above.
4. Repair or reset Microsoft Store if it appears under Settings > Apps > Installed apps.
5. Reinstall the affected app through its supported official package channel.

If every Store app fails after these steps, test the app from another Windows user account. A new account can help identify profile or package-registration corruption. If the app works there, repair or reinstall it for the affected account rather than copying DLLs between profiles.

Common causes of mrt100_app.dll errors

The error can appear after a Windows update, failed app migration, cleanup utility, permissions change, antivirus action, or interrupted Store installation. These events can damage the package relationship even when the app’s visible files still exist.

FAQ

Is mrt100_app.dll a Windows system file?

It is a genuine Microsoft runtime component, but it is normally app-local or supplied through a framework package. It is not a general-purpose DLL that every Windows installation must place in System32.

Is it part of Visual C++ Redistributable?

No. Do not install Visual C++ 2010 merely because the filename resembles a runtime component. The .NET Native runtime and Visual C++ Redistributables are different dependencies.

Should I download mrt100_app.dll separately?

No. Random DLL downloads can contain malware, the wrong architecture, or an incompatible package version. They also leave package registration and related dependencies unresolved. Use Windows Update, Microsoft Store, the app’s official installer, and Microsoft repair tools.

Will SFC restore the file?

Not necessarily. SFC checks protected Windows system files, while this DLL is generally app or framework package content. Repairing or reinstalling the affected Store app is more direct.

Why does the app work from Start but not from an .exe?

The Start shortcut launches the registered package with its manifest, permissions, and dependencies. A copied or directly launched executable may not receive that package context.

What should support receive if the problem continues?

Provide the affected app’s name, Windows 10 or Windows 11 version, exact error text, package architecture if known, Event Viewer details including any faulting module, and whether the app launches from Start but fails from a copied executable. Also mention whether the issue affects one app or several and whether Defender shows a quarantine event.

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