api-ms-win-security-sddl-ansi-l1-1-0.dll is a genuine Microsoft Windows API-set contract, but it is not necessarily a standalone DLL that you should download. If Windows reports that it is missing, not found, or could not be loaded, repair Windows first and then repair the one application that is failing.
What this file is
Windows uses API-set contracts as stable names that applications can import. The Windows loader maps those contracts to the appropriate host implementation. Consequently, the .dll name does not prove that an independently downloadable file should exist in System32, SysWOW64, or the application folder.
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Microsoft associates this contract with ANSI security-identifier functions:
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Microsoft documents these APIs as available beginning with Windows version 10.0.16299. The underlying security functionality is associated with Windows components including Advapi32.dll. See Microsoft’s documentation for Windows API sets, API-set loader operation, and the Windows API inventory.
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Version and identity check
| Item | Verified information |
|---|---|
| Name | api-ms-win-security-sddl-ansi-l1-1-0.dll |
| Product family | Microsoft Windows API-set infrastructure |
| Function area | Security identifiers and SDDL-related APIs |
| Physical file | Not guaranteed; the name may be resolved as a loader contract |
| Supported introduction | Microsoft documents the related API set from Windows 10.0.16299 |
| Official standalone download | No verified Microsoft redistributable was identified |
| Known file version, size, or hash | Not established |
This is not verified as a Visual C++ Redistributable, DirectX, .NET, or third-party runtime file. Installing one of those packages is not a justified first step unless the application reports a separate missing dependency from that runtime.
Error messages you may see
Windows may display wording such as:
The program can't start because api-ms-win-security-sddl-ansi-l1-1-0.dll is missing from your computer. Try reinstalling the program to fix this problem.
Other variants include:
The application failed to start because api-ms-win-security-sddl-ansi-l1-1-0.dll was not found.
Error loading api-ms-win-security-sddl-ansi-l1-1-0.dll.
The specified module could not be found.
“Missing” can mean that the application cannot resolve the API contract, not that a removable file has simply vanished. The failure may involve damaged Windows components, an unsupported Windows release, an incomplete application installation, antivirus quarantine, or an architecture mismatch.
Fix 1: Update Windows and restart
Start with Windows servicing because this name belongs to Windows API infrastructure.
- Open Start > Settings.
- Select Windows Update.
- On Windows 10, select Update & Security > Windows Update.
- Select Check for updates.
- Install all available quality, cumulative, and servicing updates.
- Restart the computer, even if Windows does not insist on restarting.
- Try the affected program again.
If the program now opens, the problem was likely caused by an outdated or damaged Windows component. If the same error remains, continue with DISM and SFC rather than searching for a replacement DLL.
Fix 2: Repair Windows with DISM and SFC
DISM repairs the Windows component store. SFC then checks protected system files against that repaired store. Run DISM first.
Run DISM
- Open Start and type
Command Prompt. - Right-click Command Prompt.
- Select Run as administrator.
- Approve the User Account Control prompt.
- Enter:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for the operation to finish. Do not close the window because progress may pause for a while.
- Restart Windows when DISM completes.
Run SFC
After restarting:
- Open Command Prompt as administrator again.
- Enter:
sfc /scannow
- Wait until verification reaches 100 percent.
- Restart the computer.
- Test the affected program.
If SFC reports that it repaired corrupted files, restart before testing. If it reports that it found corruption but could not repair everything, run DISM again, restart, and repeat SFC once. For persistent failures, Microsoft’s System File Checker guidance explains the next diagnostic steps.
If DISM cannot obtain repair files through Windows Update, use a known-good Windows installation source that matches the installed edition and build closely. For example:
DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:C:RepairSourceWindows /LimitAccess
Replace the example path only with a valid repair source. Microsoft documents the requirements in its guide to repairing a Windows image.
Running DISM and SFC manually is safe but can involve repeated scans and difficult-to-interpret logs. Outbyte PC Repair can scan for system problems and show what it identifies; the repair action is done by the full version, and it is optional rather than required. For an application-specific failure, reinstalling that application remains the definitive repair.
Fix 3: Determine whether one application or all applications fail
The scope of the failure changes the diagnosis.
- If several unrelated programs fail with the same API-set message, continue treating this as a Windows servicing or compatibility problem.
- If only one program fails, its installation, bundled dependencies, permissions, or compatibility is more likely to be responsible.
- If the problem began immediately after installing or updating one program, start with that program’s repair option.
- If it began after an antivirus action, inspect Protection History before reinstalling anything.
Record whether the failing process is 32-bit or 64-bit and whether Windows is 32-bit or 64-bit. Do not infer the correct repair from an online “32-bit DLL” or “64-bit DLL” label. API-set resolution, filesystem redirection, and the application’s own dependencies make manually copying a file unreliable.
Fix 4: Repair or reinstall the affected application
If only one application or game refuses to start, repair it from its original vendor or launcher.
Use Windows’ repair option
- Open Start > Settings.
- Select Apps > Installed apps.
- Find the affected program.
- Select the three-dot menu beside it.
- Choose Advanced options, if available.
- Select Repair.
- Start the program again.
If there is no Repair button, use the program’s own installer or launcher. Game launchers commonly provide a Verify files, Scan and repair, or similarly named command. Run that command while signed in to the account that owns the installation.
If verification finds damaged files, allow it to replace them and then restart the program. If verification reports no problems but the API-set error remains:
- Back up the program’s settings or saved data if necessary.
- Uninstall the program from Settings > Apps > Installed apps.
- Restart Windows.
- Download the installer only from the application developer or the original store.
- Install the current version.
- Test it before adding unofficial patches, modifications, or copied DLL files.
An older application may import an API-set contract that is unavailable on an older Windows release. Check the application’s minimum Windows requirement and update the operating system rather than substituting a DLL.
Fix 5: Check antivirus quarantine
Security software can quarantine an application file or, less commonly, interfere with a Windows component.
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- Select Virus & threat protection.
- Select Protection history.
- Review recent detections.
- Expand an entry related to the affected program.
- Do not restore anything merely because its filename resembles the missing API-set name.
- Restore or allow a file only after confirming that it belongs to the legitimate Windows installation or the application’s official, signed installation.
Run a full scan after reviewing the history. If files repeatedly disappear, disconnect the computer from untrusted networks, update Windows Security, and investigate possible malware or disk problems. The Microsoft Protection History guidance explains the available restore and allow actions.
Fix 6: Check drivers only when the evidence points there
A graphics, storage, or security driver is not an established owner of this API-set contract. Do not replace drivers simply because the filename contains .dll.
Investigate drivers if the error began after a hardware change, a driver update, a device failure, or repeated system instability:
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- Right-click Start and select Device Manager.
- Expand categories such as Display adapters, Storage controllers, and System devices.
- Look for a warning icon or a device that stopped working.
- Right-click the relevant device and choose Properties.
- Review the General and Driver tabs.
- Install drivers only from Windows Update or the hardware manufacturer.
- Restart and test the application.
Outbyte Driver Updater can scan for outdated drivers and identify which versions need attention; the driver installation is performed by the full version, and it is optional. Do not use a driver utility as a substitute for repairing Windows when DISM or SFC reports component corruption.
Fix 7: Use System Restore after a recent system change
System Restore is appropriate when the error began after a Windows update, driver installation, cleanup utility, or other system change.
- Open Start and search for
Create a restore point. - Open the matching Control Panel result.
- Select System Restore.
- Choose a restore point created before the error began.
- Select Next, review the affected programs, and select Finish.
- Let Windows restart and complete the rollback.
System Restore rolls back system files, settings, updates, drivers, and installed programs without removing personal files. It does not replace a current backup. Microsoft explains the process in its System Restore documentation.
Fix 8: Reinstall Windows while preserving files and apps
Use Windows repair reinstall only after updates, DISM, SFC, and application repair have failed, particularly when several programs show related system errors.
On Windows 11:
- Open Settings > System > Recovery.
- Find Fix problems using Windows Update.
- Select Reinstall now.
- Follow the prompts.
This reinstalls the current Windows version while preserving apps, files, and settings according to Microsoft’s documented recovery process. If the option is unavailable or the installation is severely damaged, use Windows recovery or installation media after backing up important data. Microsoft’s repair reinstall guidance describes the supported process.
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What not to do
Do not download the DLL from a random website
A third-party download may contain malware, a mismatched build, the wrong architecture, or an altered file. It may also fail because the problem is the API-set mapping, component store, application manifest, or another dependency.
There is no verified Microsoft standalone download page for this contract. Use Windows Update, DISM, SFC, the application’s official installer, and Microsoft recovery tools instead.
Do not copy it into System32 or SysWOW64
Those folders are not interchangeable drop locations. Filesystem redirection and 32-bit versus 64-bit process behavior can make manual placement ineffective or harmful. An API-set contract may not correspond to a physical file that belongs in either folder.
Do not run regsvr32 for this name
regsvr32 registers COM and ActiveX DLLs that expose registration functions such as DllRegisterServer. This API-set contract is resolved by the Windows loader and is not a normal registration-based component. Running:
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regsvr32 api-ms-win-security-sddl-ansi-l1-1-0.dll
is therefore not a valid repair. Microsoft explains the distinction in its Regsvr32 troubleshooting documentation.
FAQ
Is api-ms-win-security-sddl-ansi-l1-1-0.dll legitimate?
Yes. It is a Microsoft Windows API-set contract associated with ANSI security-identifier functions. Its legitimacy does not mean that you should download a physical DLL with that name.
Is it always stored in System32?
No. API-set names are loader contracts and may be resolved through the Windows API-set schema rather than by opening a file with the same name.
Should I install Visual C++, DirectX, or .NET?
Not for this error alone. Install or repair those runtimes only if the application separately identifies one of them as missing or damaged.
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 minuteDoes this error prove that Windows has malware?
No. Corrupted components, an old Windows release, a damaged application, antivirus quarantine, and compatibility problems can all produce loader errors. Run a full security scan if the timing or other symptoms suggest malware.
What if SFC finds no violations?
Continue with application repair if only one program fails. If many programs fail, review DISM results, Windows Update history, and recent system changes. SFC cannot repair every application or compatibility problem.
What if only a 32-bit application fails?
Check whether the application is outdated and whether its requirements support the installed Windows version. Do not download a file labeled “32-bit” and place it in SysWOW64; that does not repair API-set resolution.
When should I contact the application vendor?
Contact the vendor after Windows Update, DISM, and SFC complete successfully but the current official application build still fails. Provide the exact error text, Windows edition and build, application architecture, and whether other programs are affected.
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