api-ms-win-crt-filesystem-l1-1-0.dll: Fix Load Errors Safely

If api-ms-win-crt-filesystem-l1-1-0.dll is missing, Windows or an application cannot load part of the Microsoft Universal C Runtime that it expects. The api-ms-win-crt-filesystem-l1-1-0.dll error usually points to an incomplete Windows update, a missing Visual C++ Redistributable, a damaged application installation, or a dependency problem.

The safest repair is to restore the runtime through Windows Update, the matching Microsoft Visual C++ Redistributable, or the installer for the affected program. Do not download an isolated DLL from a random website and copy it into a Windows folder.

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What this DLL is

api-ms-win-crt-filesystem-l1-1-0.dll is a Microsoft Universal C Runtime API-set component. It acts as a forwarder or contract for filesystem-related C-runtime functions, including _access, _chdir, _mkdir, _stat, _unlink, and related wide-character APIs. Microsoft lists these functions under this exact module name in its Win32 extension API reference.

It is not:

• A DirectX graphics library
• A .NET component
• A graphics-driver DLL
• A game-specific library
• A COM or ActiveX component that should be registered manually

The Universal C Runtime became part of the Windows development and deployment model with Visual Studio 2015. Windows 10 and Windows 11 include and service the UCRT as part of the operating system. Older supported Windows versions received it through Windows Update or a Microsoft UCRT update package. Microsoft explains this model in its Universal CRT deployment documentation.

A program built with Visual Studio 2015 or later may require this runtime even when the program itself is unrelated to Microsoft development tools. Games, game launchers, database utilities, Python-based software, development tools, installers, and native Windows applications can all expose the same missing-runtime problem.

File identification

Item	What can be established safely
File	api-ms-win-crt-filesystem-l1-1-0.dll
Runtime	Microsoft Universal C Runtime
Role	API-set forwarder for filesystem-related C-runtime functions
Category	Visual C++ Redistributable or Windows runtime component
Part of	Windows servicing or the program that installed it, depending on deployment
Developer or publisher field	Not reliably listed for a particular application package
Internal name	Not dependably published by Microsoft
Current version	No single independent version applies to every Windows build
Historical Microsoft payload	Microsoft has documented a UCRT package payload with version 10.0.10240.16390; this is not a universal current version
Architecture	The application architecture must match the runtime architecture

The filename alone does not identify the program that is failing. The executable named in the error matters more than the DLL name.

Where the file belongs

For centrally deployed runtime files on 64-bit Windows, Microsoft documents these general locations:

• C:\Windows\System32 contains 64-bit system files.
• C:\Windows\SysWOW64 contains 32-bit system files.

The names are confusing but intentional. On 64-bit Windows, System32 is normally the 64-bit system directory, while SysWOW64 contains 32-bit components used by 32-bit applications.

A 32-bit application running on 64-bit Windows normally needs the x86 Visual C++ runtime and may use files associated with SysWOW64. A 64-bit application needs the x64 runtime and normally uses files associated with System32.

The file may also exist beside an application’s executable as an application-local copy. This is more common with older Windows versions, older application installers, or software vendors that package their own runtime files. Microsoft supports application-local UCRT deployment in some situations but generally recommends central deployment where it is available.

Because API-set names are loader contracts, do not assume that a visible standalone file is the only thing Windows needs. The loader may also need ucrtbase.dll, other API-set forwarders, or a dependent library.

First, identify the scope of the failure

Before changing Windows files, determine whether one program fails or several unrelated programs fail.

If only one program fails

The likely causes are:

• An interrupted installation
• A missing application-local runtime
• A corrupted private DLL
• A damaged game installation
• A missing prerequisite that the application’s installer failed to install
• A 32-bit or 64-bit mismatch

Start with the application’s Repair option, launcher verification, or official installer.

If several unrelated programs fail

The likely causes are:

• Missing Windows updates
• A damaged or incomplete UCRT installation
• A missing Visual C++ Redistributable
• Corrupted Windows component files
• Antivirus quarantine
• A system-wide architecture or servicing problem

Start with Windows Update, then repair the matching Visual C++ Redistributable.

If the error appeared after security software acted

Open Windows Security and inspect Protection History before reinstalling anything:

1. Open Start.
2. Type Windows Security.
3. Open the app.
4. Select Virus & threat protection.
5. Select Protection history.
6. Look for an action involving the application or runtime files.

Restore a quarantined file only when you can confirm that it came from a trusted Microsoft or application installer. If the file came from an unknown DLL website, do not restore it. Reinstall the official package instead.

Fix 1: Install all available Windows updates

This is the correct first step on Windows 10 and Windows 11 because the UCRT is part of Windows servicing.

Windows 11

1. Open Start.
2. Select Settings.
3. Select Windows Update.
4. Select Check for updates.
5. Install every available update.
6. Restart the computer.
7. Return to Settings > Windows Update.
8. Check again after restarting.

Launch the affected program again. If the program starts normally, the missing component was likely restored through Windows servicing.

Windows 10

1. Open Start.
2. Select Settings.
3. Select Update & Security.
4. Select Windows Update.
5. Select Check for updates.
6. Install the available updates.
7. Restart the computer.
8. Check for updates again.

Microsoft provides the current menu paths in its guide to installing Windows updates.

If Windows Update fails, record the error code and continue with the Visual C++ Redistributable repair below. Do not assume that a failed update means the DLL should be downloaded separately.

Fix 2: Install the UCRT update on older Windows

Windows 7, Windows 8, and Windows 8.1 do not receive the UCRT in exactly the same way as Windows 10 and Windows 11. The UCRT is supplied through Windows Update or the official Microsoft update package named Update for Universal C Runtime in Windows.

Before installing an update, press Windows key + R, type winver, and press Enter. Confirm the Windows edition and whether the system is x86 or x64.

Windows 7 requires Service Pack 1. Windows 8.1 requires the documented April 2014 update rollup prerequisite. Microsoft lists the supported versions and prerequisites in its Universal C Runtime update guidance.

Use the package that matches the operating system:

• Windows 7 x86 KB2999226, named Windows6.1-KB2999226-x86.msu
• Windows 7 x64 KB2999226, named Windows6.1-KB2999226-x64.msu
• Windows 8.1 x86 KB2999226, named Windows8.1-KB2999226-x86.msu
• Windows 8.1 x64 KB2999226, named Windows8.1-KB2999226-x64.msu
• Windows 7 x64 KB3118401, a later UCRT update for that platform

To install an MSU package:

1. Download it from the Microsoft Download Center.
2. Open the downloaded .msu file.
3. Accept the update installation.
4. Restart when prompted.
5. Try the affected application again.

Do not install an x64 package on x86 Windows. If the package refuses to install, check the service-pack and prerequisite requirements instead of forcing the installation.

Fix 3: Repair or install the matching Visual C++ Redistributable

The Visual C++ Redistributable is the most important application-level repair for this category of error.

Microsoft provides current Visual C++ Redistributable packages here:

• Visual C++ Redistributable downloads
• x86 vc_redist.x86.exe
• x64 vc_redist.x64.exe
• ARM64 vc_redist.arm64.exe

Choose based on the application, not only the Windows installation:

• A 32-bit application needs the x86 package.
• A 64-bit application needs the x64 package.
• An ARM64 application may need the ARM64 package.
• A 32-bit application on 64-bit Windows still needs x86.
• Many PCs need both x86 and x64 because they run programs of both architectures.

Repair an installed package

1. Open Start.
2. Select Settings.
3. Select Apps.
4. Select Installed apps.
5. Search for Microsoft Visual C++ Redistributable.
6. Open the menu beside the relevant entry.
7. Select Modify, if available.
8. Choose Repair.
9. Repeat for the other architecture if both x86 and x64 entries are installed.
10. Restart Windows.

On some Windows versions, the entry appears under Apps & features, and the available button may be Change rather than Modify.

Install a missing package

1. Download the required package from Microsoft’s official page.
2. Close the affected program.
3. Run the downloaded installer.
4. Accept the license terms.
5. Select Install or Repair, depending on what the installer offers.
6. Restart Windows.
7. Launch the affected program.

For a 32-bit program, installing only x64 is not sufficient. This is one of the most common reasons a user reports that reinstalling Visual C++ did nothing.

Repair from an elevated Command Prompt

If the installer is already downloaded, open Command Prompt as administrator, change to the folder containing the installer, and run the matching command:

vc_redist.x86.exe /repair

vc_redist.x64.exe /repair

The file name must match the installer you downloaded. Microsoft documents these redistributable command-line options in its Visual C++ deployment guidance.

If the installer fails, install pending Windows updates, restart, and try again. Microsoft also recommends checking installer logs, permissions, antivirus interference, and Windows Update prerequisites in its Visual C++ Redistributable troubleshooting guide.

Do not uninstall every Visual C++ entry. Older programs may require older redistributables, and Visual C++ 2013 and earlier packages remain side by side. Visual Studio 2015 through 2022 runtimes share binary compatibility, but that does not mean every old installer can be removed safely.

Fix 4: Repair the affected program

If only one application reports the DLL error, repair that application before changing system directories.

Repair a Windows application

1. Open Start.
2. Select Settings.
3. Select Apps.
4. Select Installed apps.
5. Find the affected application.
6. Open its menu.
7. Select Advanced options, if available.
8. Select Repair.
9. Test the application.

Microsoft describes these options in its guide to repairing apps and programs in Windows.

Traditional desktop programs may instead have their own installer:

1. Open Control Panel.
2. Select Programs.
3. Select Programs and Features.
4. Select the affected program.
5. Choose Repair or Change, if offered.
6. Complete the wizard.
7. Restart Windows.

If there is no Repair option, download the installer from the application’s official vendor and reinstall the program. Do not use a DLL-only download as a substitute for the complete installer.

Repair a game installation

Use the game launcher’s file verification feature before reinstalling the entire game. The wording differs between launchers, but the usual sequence is:

1. Open the launcher.
2. Open the game library.
3. Open the menu beside the game.
4. Select Manage, Properties, or a similar option.
5. Choose Verify, Verify files, or Repair.
6. Wait for the scan to finish.
7. Restart the launcher.
8. Test the game.

Launcher verification can restore application-local files, but it may not repair system-wide UCRT components. Combine it with Windows Update and Visual C++ Redistributable repair when the error names an API-set runtime file.

Fix 5: Check both system locations and the application folder

A file can exist while the program still fails because Windows is loading another copy or cannot load a dependency.

Open Command Prompt and run:

dir "%WINDIR%\System32\api-ms-win-crt-filesystem-l1-1-0.dll"

dir "%WINDIR%\SysWOW64\api-ms-win-crt-filesystem-l1-1-0.dll"

If the command reports that the file cannot be found, that does not by itself identify the correct repair. The expected location depends on Windows architecture, application architecture, and deployment method.

Also inspect the folder containing the failing executable:

1. Right-click the application’s shortcut.
2. Select Open file location.
3. Look for a private copy of the DLL beside the executable.
4. Do not delete or replace it manually.
5. Use the application’s Repair or reinstall option instead.

A private copy may be corrupt, incomplete, or the wrong architecture. Replacing one file can leave the rest of the UCRT set inconsistent.

Fix 6: Repair Windows components with DISM and SFC

Use Windows component repair when:

• Several programs fail
• Windows Update cannot restore the runtime
• Protected system files may be damaged
• The error appeared after an interrupted update
• The Visual C++ packages install successfully but applications still fail

Open an elevated Command Prompt:

1. Open Start.
2. Type Command Prompt.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Approve the User Account Control prompt.
6. Run DISM first:

DISM.exe /Online /Cleanup-Image /RestoreHealth

Wait for the command to finish. Then run System File Checker:

sfc /scannow

Restart Windows after both commands complete and test the affected program again.

DISM repairs the Windows component store. SFC checks protected system files against the repaired source. Microsoft documents the process in its Windows image repair guidance and SFC command reference.

A successful result does not necessarily mean that this exact DLL was the only problem. SFC may report that no integrity violations were found, that damaged files were repaired, or that some files could not be repaired. If DISM cannot find repair files through Windows Update, use a matching Windows installation source with the /Source option rather than copying a DLL from another computer.

Running DISM and SFC manually means waiting through repairs and still having to infer which component changed. Outbyte PC Repair offers a free scan that shows what it finds, while repair is handled by the full version; it is optional, and the official Windows commands remain the baseline for system-file repair.

Fix 7: Check application architecture and dependencies

The message “The specified module could not be found” does not always mean that the named DLL itself is absent. Windows may be unable to load a dependency of that DLL or of the application.

Possible causes include:

• The program is 32-bit but only the x64 runtime was installed.
• The program is 64-bit but only the x86 runtime was installed.
• A dependent DLL is missing.
• An application-local copy is damaged.
• A DLL exists in an unexpected directory.
• A file has an invalid format.
• The application installation is incomplete.

Identify the failing executable from the error message, shortcut, launcher, or installer log. Do not assume that a 64-bit Windows installation means every program on it is 64-bit.

If the application includes an installer log, inspect it for the failed prerequisite. A dependency-inspection tool can also show which module the loader could not resolve. Microsoft discusses this class of failure in its dependency troubleshooting guidance.

When the error says that the file is “not designed to run on Windows” or “contains an error,” the message can indicate a damaged dependency, invalid architecture, or malformed application-local file. It does not prove that this particular API-set file is corrupt.

Fix 8: Check antivirus quarantine

Antivirus software can quarantine a runtime file or an application-local copy. Treat this as an evidence check, not as a reason to disable security software.

1. Open Start.
2. Type Windows Security.
3. Open the app.
4. Select Virus & threat protection.
5. Select Protection history.
6. Expand any relevant detection.
7. Check the original file path and detection details.
8. Restore only if the file came from Microsoft or a trusted application installer.
9. Run a security scan afterward.

If the file came from an unknown source, do not restore it. Remove the untrusted package and reinstall the application or runtime from its official source. Microsoft explains Protection History actions in its Windows Security guidance.

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Fix 9: Update a driver only when the failing program belongs to that driver

This DLL is a UCRT component, not a graphics or hardware-driver component. Reinstalling a graphics driver will not normally restore it.

A driver update is relevant when the failing executable belongs to:

• A printer’s control software
• A device-management utility
• A hardware configuration panel
• A driver installer
• A vendor support application

To check a device driver manually:

1. Open Start.
2. Type Device Manager.
3. Open Device Manager.
4. Expand the category related to the failing hardware.
5. Right-click the device.
6. Select Properties.
7. Open the Driver tab.
8. Note the provider and driver date.
9. Select Update Driver.
10. Choose Search automatically for drivers.
11. Restart Windows if an update is installed.

You can also check Settings > Windows Update > Advanced options > Optional updates > Driver updates, when that section is available.

Finding a stale driver among many hardware entries can take time and still leave the original application runtime problem unresolved. Outbyte Driver Updater offers a free scan that identifies driver issues, while driver installation is handled by the full version; it is optional, and a driver should be changed only when the failing executable is actually tied to that hardware.

If the problem began immediately after a driver update, open the device’s Properties > Driver tab and select Roll Back Driver, if available. Do not uninstall unrelated devices merely because the error names a DLL.

What Windows Features can and cannot do

There is no normal Windows Features checkbox that installs this particular UCRT API-set component.

You can inspect the available features here:

1. Open Control Panel.
2. Select Programs.
3. Select Turn Windows features on or off.
4. Review the list.
5. Close the window without enabling unrelated features.

Do not enable .NET Framework, legacy components, or other optional features as a general DLL repair. That can add unrelated software without restoring the missing Visual C++ runtime.

What not to do

Do not download the DLL from a random website

Isolated DLL download sites can provide:

• Malware or tampered files
• The wrong architecture
• A version intended for another Windows build
• An incomplete UCRT set
• A file that does not match its dependencies

Even if the copied file removes one message, it may leave the application unable to start or hide the real installation problem. Use Windows Update, Microsoft’s UCRT package, Microsoft’s Visual C++ Redistributable, or the application’s official installer.

Do not copy the file into System32 manually

Copying a DLL into System32 can create a version mismatch and does not repair the component store, servicing metadata, registry state, or related UCRT files.

Manual application-local deployment is a developer or vendor task that should use a trusted Windows SDK or official runtime package. It is not the normal end-user repair path.

Do not run regsvr32 on this file

regsvr32 is intended for DLLs that expose registration entry points such as DllRegisterServer. An API-set/UCRT forwarder is not a COM or ActiveX component.

This is not an appropriate repair command:

regsvr32 api-ms-win-crt-filesystem-l1-1-0.dll

Running it may produce a registration error without changing the runtime installation. Microsoft explains the purpose and common errors of Regsvr32.

Do not remove all Visual C++ entries

Different applications can require different redistributable families. Removing every Visual C++ entry can create new failures for unrelated programs.

Repair the matching package first. If the affected program has its own prerequisite installer, use that installer rather than uninstalling runtimes globally.

Do not assume DirectX or .NET is the answer

This file belongs to the Universal C Runtime. Installing DirectX, enabling a .NET feature, cleaning the registry, or reinstalling a graphics driver will not normally repair this component.

When every normal fix fails

Collect the following information before contacting the application’s developer or Microsoft support:

• Exact Windows edition and build
• x86, x64, or ARM architecture
• Exact executable that fails
• Complete error text
• Any status or error code
• Whether one application or several applications fail
• Whether the DLL exists in System32
• Whether it exists in SysWOW64
• Whether a private copy exists beside the executable
• Visual C++ installer results
• Windows Update error details
• DISM and SFC results
• Antivirus Protection History entries
• Application or installer logs

If the failure began immediately after a specific update, driver installation, or application installation, System Restore may be appropriate when a suitable restore point exists:

1. Open Start.
2. Type Create a restore point.
3. Open the result.
4. Select System Restore.
5. Choose a restore point from before the change.
6. Review the affected programs and drivers.
7. Confirm the restore.
8. Restart Windows.

System Restore does not remove personal documents, but it can revert system files, registry settings, drivers, and installed programs. Microsoft describes the process in its System Restore guidance.

Frequently asked questions

Is api-ms-win-crt-filesystem-l1-1-0.dll safe?

It is a Microsoft Universal C Runtime API-set component when supplied by Windows servicing or a trusted application installer. The filename alone cannot prove that an arbitrary copy is safe. Verify the file’s location and source, and use Windows Security if antivirus software reported it.

Do I need both x86 and x64 Visual C++ packages?

Possibly. A 32-bit program needs x86 even on 64-bit Windows. A 64-bit program needs x64. Users who run both types of software commonly need both packages installed.

Will installing the latest Visual C++ Redistributable always fix the error?

No. Windows 10 and Windows 11 service the UCRT as part of Windows, while older Windows versions may require the Microsoft UCRT update package. A damaged application installation, missing dependency, wrong architecture, or corrupted Windows component store can also cause the error.

Why does the file exist but the application still fail?

The application may be loading a different copy, using the wrong architecture, or failing to load a dependency. A private copy beside the executable can also override or conflict with the centrally deployed runtime.

Should I copy the file from another computer?

No. The other computer may have a different Windows build, architecture, or runtime state. Restore the component through Windows Update, the official redistributable, or the application’s installer.

Should I register the DLL with regsvr32?

No. This is not a COM or ActiveX library that needs registration. Use runtime repair, Windows servicing, application repair, DISM, or SFC instead.

Is this a DirectX problem?

Normally, no. The file belongs to the Universal C Runtime and provides filesystem-related C-runtime APIs.

Is this a .NET problem?

Normally, no. A .NET repair may be relevant only if the failing application separately reports a .NET error. It does not normally restore this UCRT component.

Can a game launcher repair it?

A launcher can restore a missing or damaged application-local runtime file when its verification feature includes that file. It may not repair system-wide UCRT components, so also check Windows Update and the Visual C++ Redistributable.

Is the historical version 10.0.10240.16390 the version I should install?

No. That version appears in a historical Microsoft UCRT file table. It is not a universal current version for every Windows build. Let Windows servicing or the official redistributable provide the appropriate files.

What is the most likely fix on Windows 11?

Install all Windows updates, restart, repair the matching Visual C++ Redistributable, and repair the affected application. If several programs fail, run DISM followed by SFC.

What is the most likely fix on Windows 7 or Windows 8.1?

Install the required service packs and updates, then install the matching Microsoft UCRT update package. Repair or install the correct x86 or x64 Visual C++ Redistributable afterward if the application still fails.

What if only one installer reports the error?

The installer may have failed to install its prerequisites or may be running with an incomplete application-local runtime. Restart Windows, install updates, repair the matching Visual C++ package, and rerun the official installer. If it still fails, inspect the installer log.

What if antivirus removed the file?

Check Protection History and confirm the original path. Restore only a verified Microsoft or trusted application file. If the source is unknown, do not restore it; reinstall the official package and scan the system.

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