You may see “The program can’t start because api-ms-win-core-psm-appnotify-l1-1-0.dll is missing from your computer,” “The specified module could not be found,” or “The code execution cannot proceed because api-ms-win-core-psm-appnotify-l1-1-0.dll was not found.” This guide explains what api-ms-win-core-psm-appnotify-l1-1-0.dll is and how to repair the underlying Windows or application problem.
The 60-second answer
api-ms-win-core-psm-appnotify-l1-1-0.dll is a genuine Microsoft Windows API-set contract name. It is not normally a standalone runtime that you should download, copy into System32, or register with regsvr32.
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The safest repair order is:
- Install Windows updates and restart.
- Run DISM, then System File Checker.
- Verify or reinstall the affected application.
- Check antivirus quarantine.
- Confirm the Windows build and application architecture.
- If the program runs through Wine or CrossOver, repair that compatibility layer instead of native Windows.
Microsoft associates this API set with application-state notification functions introduced in Windows 10 build 10.0.16299. The documented implementation DLL for those functions is Twinapi.core.dll, not a separate redistributable package. See Microsoft’s Windows API-set architecture, API list, and function requirements.
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What this DLL name means
An API set is a loader-facing contract. Software can request a stable API-set name while Windows resolves that request to the implementation component installed in the operating system.
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That distinction matters here. The filename in the error is not necessarily the physical binary that performs the work, and it is not a normal application DLL with a public installer. The associated APIs are:
RegisterAppStateChangeNotificationUnregisterAppStateChangeNotification
The error can therefore indicate an old Windows build, damaged Windows components, an incomplete application installation, or a compatibility-layer problem. “The specified module could not be found” does not always mean that the named file alone is missing.
Fix 1: Update Windows before repairing files
An application built for newer Windows APIs can fail on an older Windows installation, including early Windows 10 builds. Start with Windows Update.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →- Press Windows + I.
- Select Windows Update.
- Choose Check for updates.
- Install every available update.
- Restart the computer, even if Windows does not insist.
- Start the affected program again.
To check the installed build:
- Press Windows + R.
- Type
winver. - Press Enter.
- Record the Windows edition and build shown in the dialog.
If the application officially requires a newer Windows release than the one installed, copying the API-set name will not make the operating system compatible. Update to a supported Windows release instead.
Fix 2: Repair Windows with DISM and SFC
Use an elevated Command Prompt. DISM should run first because it repairs the component store that System File Checker uses as its repair source.
- Open Start.
- 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 finish. It may appear to pause at a percentage for some time. Then run:
sfc /scannow
When both commands finish, restart Windows and test the application.
A successful result may say that corruption was repaired, or that no integrity violations were found. If SFC reports that some files could not be repaired, do not download a replacement DLL. Extract the relevant entries from the CBS log with:
findstr /c:"[SR]" %windir%LogsCBSCBS.log >"%userprofile%Desktopsfcdetails.txt"
If Windows Update cannot provide DISM’s repair source, Microsoft documents using a matching installation source:
DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:C:RepairSourceWindows /LimitAccess
Replace the example path with a valid source that matches the installed Windows edition and build.
Running these commands manually can mean repeating long scans without knowing which component changed. Outbyte PC Repair can scan for the underlying Windows problems, while its full version performs the repair. It is optional, and repairing or reinstalling the affected application remains the definitive fix when the application itself is damaged.
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If Windows repairs complete but only one game or application still reports the error, focus on that program.
Use the application’s repair feature
For a Microsoft Store application:
- Open Settings.
- Select Apps.
- Choose Installed apps.
- Find the application.
- Select the three-dot menu.
- Choose Advanced options.
- Select Repair.
- Test the application.
If Repair does not help, use Reset only if you are prepared for the application to lose local settings or cached data.
For a game launcher, open the game’s properties or management menu and choose Verify, Repair, or the equivalent file-checking command. Restart the launcher after the process completes.
Reinstall from the official source
Uninstall the affected program through Settings > Apps > Installed apps, restart Windows, and reinstall it using the developer’s official installer or the official store where you obtained it.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteDo not copy the API-set file into the application folder. A copied file can create an architecture mismatch, a “bad image” error, or a misleading partial repair while leaving the original Windows problem unresolved.
Fix 4: Check the application’s architecture and dependencies
A 32-bit application and a 64-bit application can have different dependency requirements. Do not choose an x86 or x64 DLL copy based only on the name in the error.
Check the application’s official system requirements and identify whether it is 32-bit or 64-bit. Also note whether Windows itself is 32-bit or 64-bit:
- Open Settings.
- Select System.
- Choose About.
- Read System type.
This API-set filename is not a Visual C++ runtime filename. Installing Visual C++ is not an inherent fix. Install or repair the Microsoft Visual C++ Redistributable only if the application requires it or reports additional files such as VCRUNTIME140.dll or MSVCP140.dll. Use the architecture that matches the application, following Microsoft’s supported Visual C++ downloads.
Fix 5: Check antivirus quarantine
Security software may quarantine a legitimate Windows component or an application file. Check the history before restoring anything.
In Windows Security:
- Open Start and type
Windows Security. - Open the app.
- Select Virus & threat protection.
- Choose Protection history.
- Review recent detections.
- Select a detection to view its path, name, and action.
Restore a quarantined file only when you have verified that it is a false positive and came from a trusted Microsoft or application-vendor source. Update security definitions and run a scan first. If malware is suspected, do not restore the file. Repair Windows or reinstall the affected application instead. Microsoft explains these actions in its Protection History guidance.
Fix 6: Update drivers only when the failure began with a device change
A display or device-driver update is not the normal repair for an API-set contract error. It becomes relevant when the problem began immediately after a graphics, chipset, storage, or other hardware change, or when the application reports additional device-related errors.
To check for driver problems:
- Right-click Start.
- Select Device Manager.
- Expand the relevant category.
- Right-click the device.
- Select Properties.
- Review the Device status message under General.
- Open the Driver tab and note the provider and date.
- Install updates only from Windows Update or the hardware manufacturer.
Outbyte Driver Updater can show which drivers are stale instead of making you hunt through Device Manager and manufacturer pages; the full version performs the driver installation. It is optional, and a driver update should not replace Windows or application repair when this API-set error is the only symptom.
Fix 7: Use System Restore if the problem is recent
If the error began after an update, driver installation, cleanup utility, or application change, System Restore may return system files and settings to an earlier state.
- Open Start.
- Type
Create a restore point. - Open the result.
- Select System Restore.
- Choose a restore point from before the failure.
- Review the affected programs.
- Start the restore process and allow Windows to restart.
System Restore normally does not remove personal files, but it can roll back system files, registry settings, drivers, and installed programs. Microsoft describes the process in its System Restore guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.If the error appears in Wine or CrossOver
A program running through Wine, CrossOver, or another compatibility layer is not using native Windows in the same way. In that situation, repairing Windows with DISM and SFC may not address the missing API contract.
Instead:
- Update the compatibility layer.
- Use the application’s recommended Windows version profile.
- Update or recreate the affected bottle or prefix if its documentation recommends that.
- Install supported runtime components through the compatibility layer.
- Reinstall the application inside that environment.
Do not copy a native Windows DLL into a Wine prefix unless the compatibility-layer documentation specifically directs you to do so. A compatibility-layer report involving a game is evidence of an environment-specific issue, not a reason for native Windows users to download the file.
Why regsvr32 is not the fix
regsvr32 registers DLLs that expose registration entry points such as DllRegisterServer. An API-set contract is not normally a user-registerable COM component.
Running this command is therefore inappropriate:
regsvr32 api-ms-win-core-psm-appnotify-l1-1-0.dll
It may produce an entry-point error and does not repair Windows component resolution. Microsoft documents regsvr32 behavior here.
Avoid random DLL downloads
There is no dedicated Microsoft download page for api-ms-win-core-psm-appnotify-l1-1-0.dll and no standalone “API Set Stub” redistributable. Random DLL repositories can provide malware, an incorrect build, or the wrong architecture. Even a genuine-looking copy may not match the installed Windows component store or application.
Use Windows Update, DISM, SFC, the official application installer, and Microsoft-supported runtime packages instead.
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FAQ
Is this filename legitimate?
Yes. Microsoft documents it as a Windows API-set contract associated with application-state notification APIs.
Is it a Visual C++ file?
No. Visual C++ may be a separate dependency of the affected program, but this filename is not itself a VC++ runtime DLL.
Which Windows versions support it?
Microsoft documents the associated APIs from Windows 10 build 10.0.16299. That requirement does not provide a complete file-presence table for every Windows edition or installation.
Should I copy it into System32 or SysWOW64?
No. Manual copying can cause version conflicts, architecture errors, or a partial repair.
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What information should I give technical support?
Provide the Windows edition and build, application name and version, exact error text, application architecture, whether it runs natively or through Wine/CrossOver, what changed before the failure, and the results of DISM and SFC.
