The error messages you may see
Windows may report:
- “The program can’t start because api-ms-win-core-string-obsolete-l1-1-0.dll is missing from your computer.”
- “The code execution cannot proceed because api-ms-win-core-string-obsolete-l1-1-0.dll was not found.”
- “There was a problem starting api-ms-win-core-string-obsolete-l1-1-0.dll. The specified module could not be found.”
- “api-ms-win-core-string-obsolete-l1-1-0.dll is either not designed to run on Windows or it contains an error.”
These messages usually appear when an application cannot resolve a Windows API dependency. They do not necessarily mean that one physical file must be copied into the program folder.
The 60-second answer
api-ms-win-core-string-obsolete-l1-1-0.dll is a Microsoft Windows API-set component, commonly described as an ApiSet Stub DLL. An API-set name is normally a loader contract that Windows redirects to an implementation DLL, so the exact filename is not guaranteed to exist as a standalone file on every Windows installation.
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Do not download it from a random DLL website, copy it into System32, or run regsvr32 on it. If several programs fail, repair Windows with DISM and SFC. If only one program fails, repair or reinstall that application and obtain a build compatible with your Windows version and system architecture.
What “obsolete” means
The word “obsolete” describes the age or status of the API contract name. It does not mean the file is malware, and it does not mean you should delete a matching Windows component.
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Windows API sets let applications call stable contract names while the loader redirects those calls to the correct host implementation. Microsoft explains this architecture in its documentation on Windows API sets and API-set loader operation.
Public Windows file inventories identify this API-set component in Windows 8 and Windows 10-era system files, including downlevel system locations. Exact files and paths vary by Windows build and architecture, so do not treat an inventory path as a universal location for Windows 10 or Windows 11.
This is not normally a Visual C++ Redistributable file. Do not install Visual C++ merely because this filename appears in the error. That runtime is relevant when the error names dependencies such as api-ms-win-crt-* or vcruntime*.dll.
Why the error happens
The likely cause depends on how widely the failure occurs.
| What you observe | More likely explanation | Best first repair |
|---|---|---|
| Several unrelated programs fail | Damaged or incomplete Windows components | DISM, SFC, updates |
| Only one application fails | Broken installation or incompatible build | Repair or reinstall the application |
Many api-ms-win-* names appear |
Wrong target Windows version, architecture, or deployment | Update or rebuild the application |
| Failure started after a security scan | Possible quarantine or cleanup | Check Windows Security history |
| A 32-bit host fails to load a DLL | Mixed 32-bit and 64-bit dependencies | Install the matching application build |
A documented example involves LabWindows/CVI DLLs loaded by NI TestStand or LabVIEW. NI reports that an unsuitable or incompletely deployed DLL can produce a long list of missing API-set dependencies, including this one. That pattern usually indicates one compatibility or deployment problem, not dozens of unrelated missing files.
Fix 1: Repair or reinstall the affected application
Use this fix first when only one game, utility, engineering tool, or older program refuses to start.
Repair it through Windows Settings
- Press Windows + I.
- Select Apps.
- Select Installed apps.
- Find the affected program.
- Select the three-dot menu beside it.
- Choose Advanced options, if available.
- Select Repair.
- Start the application again.
The Repair button may not appear for every program.
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- Press Windows + R.
- Type
appwiz.cpl. - Press Enter.
- Select the affected application.
- Choose Repair or Change.
- Follow the installer prompts.
- Restart Windows and test the program.
If no repair option exists, uninstall the application and restart Windows. Download the current installer from the software vendor or your organization’s approved software source, then install the correct build for your Windows architecture.
A repair worked if the application starts without the API-set error. If the same message returns, the installer may target a different Windows release, omit a dependency, or contain a 32-bit/64-bit mismatch. Contact the application vendor or install a newer compatible build rather than copying this API-set name manually.
Fix 2: Check 32-bit and 64-bit compatibility
A 32-bit program and a 64-bit program do not resolve Windows components in exactly the same way. On 64-bit Windows, System32 traditionally contains 64-bit system binaries, while SysWOW64 supports 32-bit binaries. The names are confusing, so do not move files between these folders.
Check the application’s installer or vendor documentation for whether it requires x86 or x64. Install the matching release and matching third-party dependencies.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesThis matters especially when:
- A 32-bit engineering host loads a vendor DLL.
- A program was moved from another computer.
- A legacy application was upgraded to Windows 10 or Windows 11.
- A developer compiled a DLL for a different target operating system.
- A program lists many missing
api-ms-win-*contracts at once.
For LabWindows/CVI, TestStand, or LabVIEW deployments, rebuild or redeploy the DLL for the target Windows system and include its required dependencies. Replacing one reported API-set filename is unlikely to correct the underlying deployment problem.
Fix 3: Repair Windows with DISM and SFC
Use this step when several programs fail, Windows components appear damaged, or the problem began after an interrupted update, cleanup, or system failure.
Run DISM
- Open Start.
- Type
Command Prompt. - Right-click Command Prompt.
- Select Run as administrator.
- Select Yes at the User Account Control prompt.
- Enter:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Press Enter.
- Wait for the operation to finish.
DISM repairs the Windows component store that SFC uses. Do not close the window while it is working.
Run System File Checker
In the same administrator Command Prompt, enter:
sfc /scannow
Press Enter and wait until verification reaches 100 percent. Microsoft documents this repair process in its guidance for DISM and SFC and System File Checker.
Restart Windows after both commands finish. Then install available updates through Settings > Windows Update > Check for updates, restart again if requested, and test the application.
If SFC says it found and repaired corrupt files, the repair may have resolved the problem. If it says it could not repair some files, repeat the process after DISM has completed successfully. If DISM says that source files could not be found, use a matching Windows installation source or proceed to an in-place repair installation. Do not use a random DLL archive as the source.
Repeating SFC and DISM without knowing what changed can make troubleshooting tedious. Outbyte PC Repair can scan for system issues and show what needs attention, while its repair functions require the full version; it is optional, and application-specific failures still require repairing or reinstalling the affected program.
Fix 4: Install pending Windows updates
An older Windows build may not provide the compatibility expected by a newer application.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
- Press Windows + I.
- Select Windows Update.
- Select Check for updates.
- Install available updates.
- Restart when prompted.
- Return to Windows Update and repeat the check until no required updates remain.
- Test the affected program.
If the program stopped working immediately after a Windows upgrade, look for an updated application build from its vendor. A legacy binary may reference API contracts that are not available in the same form on the target release.
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Fix 5: Check antivirus quarantine
If the error began immediately after a scan, inspect whether security software quarantined a Windows or application file.
- Open Start and select Windows Security.
- Select Virus & threat protection.
- Select Protection history.
- Review recent detections.
- Check the detected file’s location, publisher, and signature.
- Restore a file only when the detection is confirmed to be a false positive.
Do not restore an unknown copy simply because its filename resembles the missing dependency. If a system file is involved, run DISM and SFC instead. If you find suspicious copies outside normal Windows or application directories, run a full Microsoft Defender scan and consider an offline scan.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 6: Update drivers only when the failure points to a driver
A driver is not the usual owner of this API-set contract, but a system-level application can fail after a driver or hardware-software compatibility change.
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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →First check Settings > Windows Update > Advanced options > Optional updates > Driver updates. Install only drivers that match your hardware. You can also inspect Device Manager:
- Right-click Start.
- Select Device Manager.
- Expand the relevant category, such as Display adapters, Network adapters, or Sound, video and game controllers.
- Right-click the device.
- Select Update driver.
- Choose Search automatically for drivers.
- Restart Windows if a driver is installed.
Do not remove a working driver just because this DLL name appears in an application error. Outbyte Driver Updater can scan for outdated drivers and identify versions, while driver installation through the full version remains optional; verify every suggested driver against your hardware and vendor support.
Why regsvr32 is not the fix
Do not run:
regsvr32 api-ms-win-core-string-obsolete-l1-1-0.dll
API-set contracts are loader mappings, not ordinary application plug-ins. They generally do not provide the DllRegisterServer entry point that regsvr32 expects. The command can produce a registration error and does not restore Windows API-set redirection.
regsvr32 is appropriate only when a trusted application’s documentation specifically tells you to register a COM or ActiveX DLL that supports registration. It is not a general repair command for missing system dependencies.
Do not download or copy the DLL
Random DLL download sites sites can provide malware, an incorrect version, an incorrect architecture, or a file that does not match your Windows build. Copying a replacement into System32, SysWOW64, or an application folder can also create signature, search-order, and compatibility problems.
Use these safe sources instead:
- Windows Update and Windows servicing tools.
- The affected application’s official installer.
- A vendor-provided update or rebuilt deployment.
- Microsoft installation media for an in-place repair.
Final recovery options
If the problem continues after application repair and DISM/SFC:
Windows 11 repair reinstall
On Windows 11, open:
Settings > System > Recovery > Fix problems using Windows Update > Reinstall now
Microsoft says this reinstalls the current Windows version while repairing system files and components and preserving apps, files, and settings where supported. Follow the on-screen instructions, keep the computer connected to power, and restart when finished.
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If the error began after a recent system change:
- Open Start.
- Search for Create a restore point.
- Open it.
- Select System Restore.
- Choose a restore point from before the failure.
- Review affected programs.
- Select Finish.
System Restore changes system files and settings but does not replace a badly deployed application. Microsoft lists this and other options in its Windows recovery guidance.
Diagnostic checklist
Before requesting technical support, record:
- The exact program that fails.
- The complete error text.
- Your Windows edition and build.
- Whether Windows is 32-bit or 64-bit.
- Whether the failing application is 32-bit or 64-bit.
- Whether other programs fail.
- Whether the issue began after an update, cleanup, or security scan.
- Whether the program was copied from another computer.
- Whether the error lists one API-set name or dozens.
That information distinguishes a damaged Windows component from an application that was built for the wrong target or deployed with incomplete dependencies.
FAQ
Is api-ms-win-core-string-obsolete-l1-1-0.dll part of Windows?
Yes. It is a Microsoft Windows API-set component associated with Windows 8 and later, although the contract name is not guaranteed to appear as a standalone physical file on every installation.
Is it part of Visual C++ Redistributable?
Not normally. Install Visual C++ only when the error identifies a Visual C++ dependency such as vcruntime*.dll or api-ms-win-crt-*.
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Does a specific game own this DLL?
No specific game or third-party publisher is identified as its owner. A program may reference the Windows API contract because of how it was built.
Why are dozens of api-ms-win-* files missing?
That usually points to an incompatible binary, wrong architecture, incorrect deployment target, or a dependency-resolution failure. Repairing one filename rarely solves the complete problem.
Should I delete the word “obsolete” file?
No. Do not delete or rename Windows API-set components.
What is the safest first step?
Repair the affected application if only one program fails. If multiple programs fail, run DISM, then SFC, restart Windows, and install pending updates.
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What if every repair fails?
Use Windows 11’s repair reinstall where available, or use System Restore and Microsoft installation media. Keep the application vendor involved when the failure is limited to one legacy or professionally compiled program.
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