The error messages you may see
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Windows may display one of these messages when an application, installer, launcher, or native library fails to load:
- “The program can’t start because api-ms-win-core-interlocked-l1-2-0.dll is missing from your computer.”
- “The code execution cannot proceed because api-ms-win-core-interlocked-l1-2-0.dll was not found.”
- “Error loading api-ms-win-core-interlocked-l1-2-0.dll. The specified module could not be found.”
- “The application was unable to start correctly.”
- “The procedure entry point could not be located.”
- “The DLL is either not designed to run on Windows or it contains an error.”
api-ms-win-core-interlocked-l1-2-0.dll is a genuine Microsoft Windows API-set contract name. It is not automatically a standalone file that should be downloaded and copied into a program folder.
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The 60-second answer
First identify the program named in the error dialog. Repair or reinstall that application from its original vendor, then restart Windows and try again. If several Windows programs fail, repair Windows itself with DISM and SFC.
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This filename represents a Windows loader contract for interlocked and singly linked list functions. Microsoft explains that API-set names ending in .dll can be virtual aliases rather than physical files on disk. The loader uses the API-set schema to redirect the request to an implementation DLL such as KernelBase.dll.
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Do not begin with a DLL download site, a copied file from another computer, or regsvr32. Those actions can install the wrong architecture, fail to recreate Windows API mappings, or introduce unsafe code.
What this file actually is
The contract covers Windows functions including:
InitializeSListHeadInterlockedFlushSListInterlockedPopEntrySListInterlockedPushEntrySListInterlockedPushListSListExQueryDepthSList
Microsoft documents these APIs in its Win32 API table. The API-set design is explained in Microsoft’s documentation for Windows API sets and API-set loader operation.
This is not normally a Visual C++ Redistributable DLL, graphics-driver DLL, DirectX file, or .NET runtime file. An application may reference the contract because it was built against Windows APIs, but that does not prove that a physical file with this exact name belongs in its installation directory.
The contract’s documented APIs were introduced with Windows 10 version 10.0.10240, and several were later moved to the api-ms-win-core-interlocked-l1-1-0 contract in version 10.0.16299. Older Windows releases may contain historical files with this name, but those records are not a universal replacement guide for current Windows installations.
What caused the failure
The likely cause depends on whether one program or Windows generally is affected.
| What you observe | More likely cause | Correct direction |
|---|---|---|
| One application fails | Incomplete application files or incompatible build | Repair, update, or reinstall that application |
| An installer or launcher fails | Missing bundled dependency or unsupported Windows version | Obtain a current installer from the vendor |
| Several unrelated programs fail | Damaged Windows components | Run DISM, then SFC |
| The issue began after an update or downgrade | API compatibility problem | Install supported application and Windows updates |
| Antivirus recently quarantined a file | Quarantine or incomplete installation | Verify the path and restore only trusted Microsoft files |
| A vendor DLL or engineering tool fails | Incompatible compiled dependency | Ask the vendor for a rebuild supporting your Windows version |
The named DLL can also be where loading stopped rather than the real missing component. A transitive dependency, such as a runtime required by the application’s own DLL, may be missing behind the first error.
Fix 1: repair the program that triggers the error
This is the safest first repair when only one application refuses to start.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errors- Close the affected application and its launcher.
- Open Settings with Windows + I.
- Select Apps, then Installed apps.
- Find the affected program.
- Select the three-dot menu beside it.
- Choose Advanced options, if available.
- Select Repair, wait for it to finish, and test the program.
- If Repair is unavailable or does not help, select Reset only if you have backed up the program’s settings and saved data.
- For desktop software without those options, open Control Panel, select Programs, choose Programs and Features, right-click the application, and select Repair or Change.
- Restart Windows and test again.
If the repair fails, uninstall the program and reinstall it using the developer’s official installer or the official platform that supplied it. Preserve documents, profiles, save files, templates, and license information first.
Do not copy api-ms-win-core-interlocked-l1-2-0.dll into the application folder. A reinstall should restore the application’s own files and dependencies, while Windows supplies the API-set mapping.
If the application is a LabWindows/CVI, TestStand, or LabVIEW deployment, check the vendor’s dependency guidance and target Windows support. NI specifically discusses this type of dependency-loading failure and recommends compiling for the target operating-system version in its dependency-loading guidance. A vendor rebuild may be required when the program was compiled against an API contract unavailable on the target system.
Check antivirus quarantine
- Open Windows Security.
- Select Virus & threat protection.
- Select Protection history.
- Look for an event that names the affected application or a Microsoft Windows path.
- Do not restore a file merely because its filename looks familiar.
- Restore only a file from the original trusted installation or a Microsoft-signed Windows location, and only when your security administrator or the vendor confirms it was a false detection.
If the file is in an unexpected application folder, verify its digital signature and origin before allowing it back. A file with this name is not genuine solely because its name matches the API-set contract.
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Fix 2: update Windows and repair its components
Use this path when several Windows programs fail, Windows features are malfunctioning, or the problem began after an interrupted update, disk issue, or system restore.
Install pending updates
- Open Settings.
- Select Windows Update.
- Select Check for updates.
- Install all available updates.
- Restart when prompted.
- Check for updates again after restarting.
- Test the affected application.
Run DISM, then SFC
- Select Start and type
Command Prompt. - Right-click Command Prompt.
- Select Run as administrator.
- Approve the User Account Control prompt.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for DISM to complete.
- Run:
sfc /scannow
- Restart Windows and test the application.
Microsoft recommends DISM before SFC because DISM can repair the component store that SFC uses. The official System File Checker instructions cover the result messages and next steps.
If DISM reports that repair files cannot be found, use a matching Windows installation source with /Source and /LimitAccess. The source must match the Windows edition and build; an arbitrary ISO can make the repair worse. Microsoft documents these options in its Windows image repair guidance.
Repeating SFC and DISM will not make an application compatible with an unsupported Windows release. If Windows repairs successfully but the same application still fails, return to the application repair and vendor-compatibility steps.
When manually checking component corruption and repeating DISM/SFC leaves you unsure what changed, Outbyte PC Repair can show its scan findings; repairs are performed by the full version, and it is optional rather than a requirement for this Windows API error.
Fix 3: check Windows and application architecture
A 32-bit application on 64-bit Windows runs through the 32-bit compatibility environment. A 64-bit application uses 64-bit Windows components. The correct repair is determined by the program that fails, not by the apparent size or name of a downloaded DLL.
To check Windows:
- Open Settings.
- Select System.
- Select About.
- Read System type under Device specifications.
- Read the Windows edition and version under Windows specifications.
To check the application, consult its official system requirements or installer. If the program is an older 32-bit application, install its supported 32-bit build. If it requires a newer Windows release, install a compatible version rather than forcing a contract file onto an older system.
Do not assume that System32 means “the 32-bit folder.” On 64-bit Windows, Windows uses filesystem redirection, and manually placing files in System32 or SysWOW64 can create a second problem.
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Fix 4: install Visual C++ only when the application needs it
The Visual C++ Redistributable is appropriate when the application also reports missing files such as MSVCP*.dll or VCRUNTIME*.dll, or when the application vendor specifically requires it. It is not the general fix for an API-set contract error.
Use Microsoft’s latest supported Visual C++ Redistributable page. Select the architecture required by the application:
Restart after installation and test the application. Visual Studio 2017 and later share the v14 redistributable family, while Visual C++ 2013 and earlier remain separate side-by-side runtimes. Install older packages only when the vendor or dependency report identifies that requirement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 5: do not register this API-set with Regsvr32
regsvr32 is for DLLs that provide registration entry points such as DllRegisterServer, typically COM components. It does not recreate Windows API-set schema mappings.
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Running this command against the contract is therefore not a repair:
regsvr32 api-ms-win-core-interlocked-l1-2-0.dll
It may produce an entry-point error or another misleading result. Microsoft explains the limits of regsvr32 in its DLL registration troubleshooting documentation.
Fix 6: investigate drivers only when the failing program identifies one
Device Manager is not a general repair tool for this API contract. Use it only if the error appears while launching software that directly depends on a device or driver.
- Right-click Start.
- Select Device Manager.
- Expand the device category named by the application or vendor.
- Right-click the device and select Properties.
- Read the General and Driver tabs.
- Use Update driver only with a driver supplied by the device manufacturer or Windows Update.
- Restart and test the program.
Do not use a driver update to repair an unrelated application dependency. When manually checking many device versions is the problem, Outbyte Driver Updater can show its scan findings; driver installation is performed by the full version, and it remains optional.
Why random DLL downloads are unsafe
Avoid sites offering a single downloadable copy of api-ms-win-core-interlocked-l1-2-0.dll. A downloaded file may have the wrong architecture, an incompatible contract generation, an invalid signature, or malicious modifications. Even a genuine historical file may not match your Windows installation and may not repair the dependency chain.
The safe sources are:
- Windows Update and Microsoft’s built-in repair tools
- The original application developer’s installer
- The official Microsoft Visual C++ packages when independently required
- A Windows repair install using matching Microsoft media
If a file appears in an application directory, verify its signature and path rather than assuming that replacing it is safe.
FAQ
Is api-ms-win-core-interlocked-l1-2-0.dll a real Windows file?
The name is genuine, but it identifies an API-set contract. The contract may be represented through Windows loader metadata and redirected to a host DLL rather than existing as a standalone file.
Should I download it into System32?
No. Copying a file into System32, SysWOW64, or the application directory does not repair API-set mappings and can introduce the wrong architecture or unsafe code.
Is this a Visual C++ problem?
Not by itself. Install Visual C++ only when the application also requires that runtime or its vendor specifically identifies it as a dependency.
Will DISM and SFC fix the error?
They can repair damaged Windows components. They cannot make an application built for an unsupported Windows version compatible.
Does the error prove that Windows is corrupted?
No. If only one application fails, an incomplete installation, missing transitive dependency, or incompatible application build is more likely.
What information should I send the vendor?
Provide the complete error text, the executable or launcher name, Windows edition and build, application architecture, what changed immediately beforehand, antivirus quarantine details, and any dependency report. This lets the vendor determine whether it needs to repair the package or rebuild the application for your Windows release.
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