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You may also see “The specified module could not be found,” “There was a problem starting api-ms-win-core-winrt-string-l1-1-0.dll,” or “api-ms-win-core-winrt-string-l1-1-0.dll is either not designed to run on Windows or it contains an error.”
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The 60-second answer
api-ms-win-core-winrt-string-l1-1-0.dll is a Windows API-set contract used for Windows Runtime string functions. It is not an ordinary third-party DLL and is not a Visual C++ Redistributable file.
Do not download a replacement from a DLL website. The name is a virtual alias that Windows can redirect to a host system DLL, so a physical file with this exact name may not exist in C:WindowsSystem32 or C:WindowsSysWOW64. Microsoft explains this API-set design in its Windows API sets documentation.
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The most common cause is an application built for a newer version of Windows being launched on Windows 7, Vista, XP, or another unsupported release. If you are using Windows 10 or Windows 11, install pending updates, repair Windows, and then repair or reinstall the application that displays the error.
Why this error appears
The filename identifies an API contract, not a normal runtime package. An application asks Windows for a particular API-set name, and the Windows loader maps that request to the appropriate implementation for that operating-system build.
That is why searching for the exact filename in System32 or SysWOW64 can be misleading. The alias might not be present as a standalone file at all. Its absence does not automatically prove that Windows has deleted a DLL.
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Windows 7 users see this error frequently because newer applications increasingly depend on Windows Runtime APIs that are not available on that operating system. Reports have involved Microsoft PowerToys, SteelSeries Engine, Jellyfin Media Player, Pro Tools First, and custom C++ programs. A newer application build may therefore fail before its main window opens, even when the application was installed correctly.
The decisive questions are:
- Which application shows the message?
- Which Windows release and build are installed?
- Does that application officially support the installed Windows version?
- Does the application fail for every Windows user, or only on this computer?
Check Windows compatibility first
On Windows 7, Vista, or XP
Treat this primarily as a compatibility problem. Installing Visual C++, DirectX, .NET, or a driver package will not add a missing Windows API contract to an unsupported operating system.
Your practical choices are:
- Upgrade to a supported Windows release and install the current application version.
- Install an older application release that explicitly supports your Windows version.
- Contact the application publisher if its support requirements are unclear.
Do not assume that installing every available Windows update will make a newer application compatible. The required API may simply not exist on the older operating system.
On Windows 10 or Windows 11
The application may require a newer Windows build, or the Windows component store may be damaged. Check the operating-system version before changing anything:
- Press
Windows+R. - Type
winver. - Press Enter.
- Note the Windows edition and version shown in the window.
- Check the application publisher’s requirements for that release.
Then install updates:
- Open Start → Settings.
- Select Windows Update.
- Choose Check for updates.
- Install all available updates.
- Restart the computer, even if Windows does not immediately require it.
- Try the application again.
Windows Update is useful for bringing a supported installation current, but it is not guaranteed to create a file with this exact name.
Repair Windows system components
Use this step when a supported Windows 10 or Windows 11 system began showing the error after an interrupted update, disk problem, malware cleanup, aggressive system cleanup, or other system damage.
- Right-click Start.
- Choose Terminal (Admin) or Windows PowerShell (Admin).
- Select Yes when User Account Control asks for permission.
- Run this command and wait for it to finish:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- When DISM completes, run:
sfc /scannow
- Wait until SFC reaches 100 percent.
- Restart Windows.
- Return to Settings → Windows Update and install any remaining updates.
- Test the affected application.
DISM repairs the Windows image that system-file checking relies on. SFC checks protected Windows files and repairs corrupted copies where possible. Microsoft documents these commands in its System File Checker instructions.
If DISM reports that the source files cannot be found, restart the computer, confirm that Windows Update is working, and run the command again from an administrator terminal. If SFC reports that it could not repair some files, restart and repeat the check once after DISM has completed. Persistent repair failures may require a Windows recovery repair or support from Microsoft.
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Repair or reinstall the affected application
If Windows is supported and system repair completes normally, focus on the application named in the error.
For a conventional desktop program
- Save your work and close the application.
- Open Settings → Apps → Installed apps.
- Find the affected program.
- Select the three-dot menu beside it.
- Choose Uninstall, if no repair option is available.
- Restart Windows.
- Download the current installer from the application publisher’s official website.
- Install it and test the program.
If the application has its own updater or repair option, use that first. Do not replace a program file with a DLL copied from another computer.
For a Microsoft Store application
- Open Settings → Apps → Installed apps.
- Select the application’s three-dot menu.
- Choose Advanced options.
- Select Repair.
- Test the application.
- If Repair does not help, use Reset only after checking whether it removes the application’s local settings or data.
- Reinstall the application from Microsoft Store if necessary.
The exact buttons can differ by Windows release and application.
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Use the launcher’s built-in file verification or repair command. The wording varies:
- Open the game launcher.
- Open the game’s properties, manage, or settings menu.
- Select Verify, Verify integrity, Repair, or the equivalent command.
- Wait for the scan to finish.
- Allow the launcher to replace damaged game files.
- Restart the launcher and test the game.
If the game still fails, reinstall prerequisites from the game’s official installation folder or publisher instructions. There is no evidence that DirectX supplies this particular Windows API-set contract, so installing unrelated DirectX packages is not a reliable first step.
Check antivirus quarantine
Security software can quarantine the application itself or a genuine dependency beside it.
- Open Windows Security.
- Select Virus & threat protection.
- Choose Protection history.
- Look for an event that matches the application and the time the failure began.
- Confirm that the installer came from the publisher before taking action.
Restore a quarantined file only when the detection is confirmed as a false positive and the program came from a trusted official source. If you are unsure, leave the file quarantined and reinstall the application from its official installer instead. Never restore or download an unknown DLL merely because its filename resembles the error message.
Check application architecture
A 32-bit application and a 64-bit application can use different dependencies. Identify the application’s architecture from its publisher’s download page or support documentation, then install the build intended for your Windows installation.
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This matters especially when the application also reports errors involving files such as MSVCP140.dll or VCRUNTIME140.dll. Those are Visual C++ runtime errors and are separate from the Windows API-set error.
If the application separately requires Visual C++ Redistributable:
- Confirm whether it needs x86, x64, or ARM64.
- Download the matching package from Microsoft’s latest supported Visual C++ Redistributable page.
- Install it.
- Restart Windows.
- Test the application again.
Installing the x64 package does not necessarily satisfy an x86 application. Visual C++ Redistributable can repair a separate C/C++ runtime dependency, but it does not provide api-ms-win-core-winrt-string-l1-1-0.dll.
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Drivers and Windows Features are not the first fix
A graphics, chipset, or storage driver can cause an application to fail for other reasons, but driver packages do not install this API-set contract. Do not use Device Manager as a substitute for checking Windows compatibility.
If the affected program is a game or hardware-dependent application, update the relevant driver after repairing Windows and the application:
- Right-click Start.
- Select Device Manager.
- Expand the relevant category, such as Display adapters.
- Right-click the device.
- Choose Update driver.
- Select Search automatically for drivers.
- Restart Windows if a driver is installed.
For graphics drivers, the hardware manufacturer’s official support page may provide a newer package than Windows Update. Outbyte Driver Updater offers a free scan showing which drivers appear outdated, while driver installation is handled by the full version; it is optional and cannot replace fixing an unsupported Windows or application build.
Likewise, do not enable random items under Control Panel → Programs → Turn Windows features on or off. This API-set contract is not added by toggling a generic Windows feature.
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Do not use regsvr32
regsvr32 is for registering certain DLLs that expose registration functions, commonly COM components. This API-set name is not a conventional COM library that users should register.
Running commands such as these will not create a missing Windows API contract:
regsvr32 api-ms-win-core-winrt-string-l1-1-0.dll
It may instead produce another error, because the named file may not physically exist and may not be registerable.
Do not copy the file from another computer
Copying a file from another Windows installation is unsafe and usually ineffective:
- The file may be a virtual alias rather than a real standalone file.
- API-set mappings depend on the Windows loader and operating-system version.
- A copied file may have the wrong architecture.
- It may not match the application or Windows build.
- It can conceal the actual compatibility or system-repair problem.
Do not place downloaded DLLs in System32 or SysWOW64. Random DLL catalogs can provide malware, an unrelated file, or a file that does not solve the loader failure.
If the error remains
Use this order:
- Confirm the exact Windows version with
winver. - Confirm the application’s minimum supported Windows version.
- Install Windows updates.
- Run DISM and SFC as administrator.
- Repair or reinstall the affected application.
- Check antivirus history.
- Verify game files if the affected program is a game.
- Check whether the application has separate x86, x64, or ARM64 builds.
- Contact the application publisher with the full error text and Windows version.
If several unrelated applications begin reporting missing system files, stop reinstalling individual runtimes. Prioritize Windows repair, malware investigation, disk-health checks, and System Restore. If the error continues on a fully updated Windows 10 or Windows 11 system after DISM, SFC, and application reinstall, the named API set may only be the first dependency failure. The application publisher’s dependency or diagnostic tools may be needed.
FAQ
Does this file need to exist in System32?
No. Microsoft describes API-set names as virtual aliases, so an exact physical file may not appear in System32 or SysWOW64.
Will Visual C++ Redistributable fix it?
Not directly. Visual C++ Redistributable fixes Microsoft C and C++ runtime dependencies. It does not install this Windows API-set contract.
Is this a 32-bit or 64-bit DLL?
The filename alone does not answer that question. The application’s architecture and the Windows build determine which loader path and dependencies are relevant.
Can Windows Update restore the file?
Windows Update can repair and update a supported Windows installation, but it is not guaranteed to place a file with this exact name on disk. The main goal is a compatible, healthy Windows build.
What is the fix for Windows 7?
Use an application release that officially supports Windows 7, or upgrade Windows. A redistributable package cannot retrofit newer Windows APIs into Windows 7.
Should I install .NET, DirectX, or a driver package?
Only if the application separately requires that component. None should be treated as the source of this API-set contract.
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