adsiis.dll is the IIS ADSI Provider DLL, and Windows may report that adsiis.dll is missing, was not found, or could not be loaded. These errors usually point to damaged or missing IIS components, IIS 6 compatibility features, a dependency problem, or a failed Windows role change rather than a random application DLL problem.

The exact errors you may see

Common Windows loader messages include:

The program can't start because adsiis.dll is missing from your computer.
Try reinstalling the program to fix this problem.

adsiis.dll was not found.

Error loading adsiis.dll.
The specified module could not be found.

The code execution cannot proceed because adsiis.dll was not found.

IIS administration can also fail without a simple missing-file dialog. IIS Manager or Server Manager may show a blank page, MMC may crash, or the crash report may identify adsiis.dll as the faulting module.

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The 60-second answer

Do not download adsiis.dll from a DLL website and do not copy an old version from another PC.

adsiis.dll is a Microsoft Windows IIS component. It provides the older ADSI interface used to query and configure IIS metabase data, including websites, virtual directories, application pools, and related administration objects. Microsoft documents the IIS ADSI provider as part of its ADSI service-provider system and IIS administration model.

Open Command Prompt as administrator and run these commands in order:

DISM.exe /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Restart Windows when both commands finish. If the error remains, repair or install IIS and the required IIS 6 Management Compatibility features. On applicable Windows Server versions, the relevant feature may appear as IIS 6 Metabase Compatibility or IIS-Metabase.

The normal location on supported Windows Server installations is:

C:WindowsSystem32inetsrvadsiis.dll

That path is not a guarantee that every Windows 10 or Windows 11 computer should contain the file. IIS and its legacy compatibility components are optional.

What adsiis.dll does

adsiis.dll has the internal description ADs IIS Provider DLL and ships as part of Microsoft Windows. It is not a Visual C++ runtime, DirectX file, .NET component, or game-runtime DLL.

The DLL belongs to IIS and the older IIS administration interfaces. Legacy scripts and applications may use the IIS ADSI provider to access configuration objects through APIs that originated with the IIS metabase. This is why the error may appear while using:

• IIS Manager or Server Manager
• IIS 6 administration tools
• SMTP administration
• Exchange setup or maintenance
• adsutil.vbs
• Older deployment scripts
• Applications built for older IIS management APIs

IIS 6 Management Compatibility exists to support applications and scripts that still use the older IIS Admin Base Object and ADSI interfaces. Microsoft describes this feature as forward compatibility for older administration software.

Where the file should be

On a supported Windows Server installation, check:

C:WindowsSystem32inetsrvadsiis.dll

Some historical 64-bit Windows Server releases also used architecture-specific locations involving:

C:WindowsSysWOW64inetsrv

Do not treat System32 and SysWOW64 as interchangeable folders. Windows uses filesystem redirection so that 32-bit and 64-bit processes receive the appropriate system components. A file from an older server release, another Windows build, or a different processor architecture is not a safe replacement.

Historical Microsoft documentation lists substantially different file versions across IIS and Windows releases. There is no universal file size, version, hash, or replacement copy that applies to every installation.

To check whether IIS is installed, open PowerShell as administrator and run:

Get-WindowsFeature *IIS*

This command applies to Windows Server. On Windows client editions, use Turn Windows features on or off instead.

What usually causes the error

Symptom	Likely cause	Best response
Windows says the file is missing	Damaged Windows component or absent IIS feature	Run DISM and SFC, then inspect IIS features
IIS Manager crashes in adsiis.dll	IIS compatibility defect, damaged component, or update issue	Repair Windows and update the server
Legacy setup refuses to continue	IIS 6 compatibility feature is absent	Install the required compatibility components
Antivirus reports or quarantines the file	Quarantine or possible false positive	Check Protection History and verify the original path
The file exists but will not load	Missing dependency, architecture mismatch, or corruption	Repair the component and identify the failing process
The problem began after a role change	Incomplete IIS installation or servicing failure	Reinstall the role or use System Restore if appropriate
Scans hang on an old backup copy	Possible disk or filesystem problem	Check disk health and Windows servicing logs

A missing-file message does not always mean adsiis.dll itself is absent. “The specified module could not be found” can also mean that a dependency required by the DLL is unavailable.

Fix 1: Repair Windows components with DISM and SFC

This is the safest first repair when the DLL is missing, corrupted, or damaged after an update, disk problem, or failed server-role change.

Step 1: Open an elevated Command Prompt

1. Press the Windows key.
2. Type cmd.
3. Right-click Command Prompt.
4. Select Run as administrator.
5. Select Yes at the User Account Control prompt.

Step 2: Repair the Windows component store

Run:

DISM.exe /Online /Cleanup-Image /RestoreHealth

DISM checks the Windows component store and repairs damage using an appropriate Windows repair source. Let it finish even if progress appears to pause.

Step 3: Repair protected system files

After DISM completes, run:

sfc /scannow

SFC checks protected Windows files and replaces corrupted copies with repaired versions from the component store.

Step 4: Restart and test

Restart Windows, then open the program that produced the error. If the failure involved IIS Manager, Server Manager, SMTP administration, or an Exchange installer, test that same operation again.

A successful result may say that SFC found no integrity violations or repaired corrupted files.

If DISM fails to find source files, do not substitute a downloaded DLL. Use a matching Windows installation or network repair source that corresponds to the installed edition and build. Microsoft’s repair-image documentation explains how to provide a suitable source.

If SFC says it could not repair some files, review:

C:WindowsLogsCBSCBS.log

Then rerun DISM with a matching repair source and run SFC again.

Repeating SFC without checking what DISM repaired can leave you guessing about the actual change. Outbyte PC Repair can show a scan of detected Windows problems, while its repair functions require the full version; it is optional, and Microsoft’s DISM and SFC remain the primary repair path.

Fix 2: Install IIS and IIS 6 Management Compatibility

If IIS or its legacy management components are absent, repairing Windows files will not create a feature that has never been installed.

On Windows Server

1. Open Server Manager.
2. Select Manage.
3. Select Add Roles and Features.
4. Continue through the wizard until Server Roles appears.
5. Expand Web Server (IIS).
6. Expand Management Tools.
7. Select IIS Management Console if IIS Manager is needed.
8. Expand IIS 6 Management Compatibility.
9. Select IIS 6 Metabase Compatibility.
10. Select any additional IIS 6 management component specifically required by the application.
11. Continue through the wizard.
12. Select Install.
13. Restart if prompted.

Feature names vary by Windows Server generation. Confirm the available names with:

Get-WindowsFeature *IIS*

For a standard IIS installation with management tools, Microsoft also documents this PowerShell command:

Install-WindowsFeature Web-Server -IncludeManagementTools

That command installs the Web Server role and management tools. It does not replace the need to select the exact IIS 6 compatibility component required by a legacy application.

On Windows 10 or Windows 11

1. Press Windows + R.
2. Type:

text
optionalfeatures

1. Press Enter.
2. Expand Internet Information Services.
3. Expand Web Management Tools.
4. Expand IIS 6 Management Compatibility if shown.
5. Select the compatibility feature required by the application.
6. Select OK.
7. Allow Windows to install the components.
8. Restart Windows if prompted.

If Internet Information Services is not listed, the installed Windows edition may not support that optional feature, or the component store may need repair first.

Confirm the installation

After restarting, open the relevant program again. For a legacy script, run the same script from an elevated Command Prompt. For IIS Manager, open it from the Start menu and navigate to the same server or site that previously failed.

If the application still reports adsiis.dll, check its documentation for a specific requirement such as IIS 6 Metabase Compatibility or IIS 6 Scripting Tools. Installing only the modern IIS console may not satisfy an older installer.

Fix 3: Check Windows Security quarantine

Antivirus software can quarantine a genuine system component, but you should not assume every detection is a false positive.

1. Open Windows Security.
2. Select Virus & threat protection.
3. Select Protection history.
4. Look for an event involving adsiis.dll.
5. Expand the event and inspect the original path.
6. Confirm that the path belongs to the Windows IIS installation, such as:

text
C:WindowsSystem32inetsrvadsiis.dll

1. Check the file’s publisher and digital signature where available.
2. Restore it only if the path, signature, and installation context are consistent with the installed Windows component.
3. Run a full security scan.
4. Repair Windows with DISM and SFC afterward.

Do not broadly disable antivirus protection. Do not restore a file merely because its name matches the missing DLL. A file in a user download folder or an unfamiliar application directory needs separate investigation.

Fix 4: Investigate disk or filesystem corruption

If antivirus scanning hangs on adsiis.dll, Windows servicing reports unreadable files, or the error began with other file corruption, the disk or filesystem may be involved.

First run the Windows component repair commands from Fix 1. Then inspect Event Viewer:

1. Press Windows + X.
2. Select Event Viewer.
3. Open Windows Logs.
4. Select System.
5. Look for recent disk, NTFS, storage, or filesystem errors.

Back up important data before performing disk repairs. Use the disk-check method appropriate for the installed Windows version and storage hardware. A historical Microsoft case involving an old service-pack backup copy attributed the problem to possible disk corruption, but that diagnosis does not apply to every adsiis.dll failure.

If other files are becoming unreadable, treat this as a storage-health problem rather than simply an IIS problem.

Fix 5: Check architecture and dependencies

A 32-bit application and a 64-bit IIS management process may not load the same architecture-specific components. Do not copy adsiis.dll between System32 and SysWOW64.

Identify the failing process:

1. Note the exact program that crashes.
2. Check whether it is a 32-bit legacy application or a 64-bit Windows tool.
3. Confirm that the required IIS compatibility feature is installed for that environment.
4. Repair the IIS role rather than replacing individual files.
5. Install pending Windows updates and restart.

If adsiis.dll exists but Windows says “The specified module could not be found,” a dependency may be missing. The named DLL is not necessarily the only missing component. Event Viewer, the application’s setup log, or Windows Error Reporting may identify the process and faulting module.

Do not use regsvr32 as a general repair command. regsvr32 registers DLLs that expose a registration entry point such as DllRegisterServer; it does not restore Windows files, repair IIS, rebuild the component store, or install dependencies. Running it against adsiis.dll is generally not the correct fix.

Fix 6: Update Windows and repair the failing application

Install pending Windows updates:

1. Open Settings.
2. Select Windows Update.
3. Select Check for updates.
4. Install applicable updates.
5. Restart.
6. Test IIS administration again.

If only one old application fails, repair or reinstall that application after confirming its IIS requirements. An Exchange-era installer, SMTP tool, or legacy administration script may require IIS 6 compatibility even when modern IIS itself appears healthy.

A driver update is not a first-line fix for adsiis.dll, because this is an IIS system component rather than a hardware driver. If the same incident includes storage-controller, chipset, or filesystem instability, identify the exact hardware first through Device Manager:

1. Press Windows + X.
2. Select Device Manager.
3. Expand the relevant hardware category.
4. Right-click the device.
5. Select Properties.
6. Open the Driver tab.
7. Note the provider, date, and version.
8. Obtain the driver from the PC, motherboard, storage, or hardware manufacturer.

Avoid replacing drivers merely because a DLL error appeared. Outbyte Driver Updater can scan for outdated drivers, but the full version is required to install updates; use it only when a genuine hardware-driver issue is also present, not as a substitute for IIS servicing.

Fix 7: Use System Restore or reinstall the IIS role

Use System Restore when the problem began immediately after a Windows update, feature change, or software installation and a suitable restore point exists.

1. Press the Windows key.
2. Search for Create a restore point.
3. Open it.
4. Select System Restore.
5. Choose a restore point created before the failure.
6. Review the affected programs and drivers.
7. Start the restoration.

System Restore can revert system files, registry settings, drivers, and installed programs without removing personal files. It does not replace a backup, and it may not be available on every system.

If IIS remains broken, remove and reinstall the IIS role only after documenting the current configuration and confirming that the server can be safely serviced. A clean role reinstall may be appropriate when the feature installation itself is damaged. For a broader Windows component failure, use a matching repair source or an approved Windows Server repair procedure.

Why random DLL downloads do not solve this

Downloading adsiis.dll from an unofficial DLL site is risky because the file may contain malware, belong to a different Windows build, use the wrong architecture, lack a valid Microsoft signature, or depend on other missing components.

Copying it into both System32 and SysWOW64 can make the situation worse. It may produce version mismatches, loader errors, or a system that appears repaired until the next update. Manual copying also bypasses Windows servicing, which is the mechanism that keeps system files, manifests, dependencies, and component versions consistent.

The safe sources are:

• Windows Update
• DISM using a matching Windows repair source
• SFC
• Windows optional features
• Server Manager and the IIS role installer
• A Microsoft installation or recovery source matching the installed edition and build

FAQ

Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Support on Ko-Fi

Is adsiis.dll a Microsoft file?

Yes. It is the Microsoft ADs IIS Provider DLL, part of Windows and IIS-related components. It is not a third-party game runtime.

Does every Windows 10 or Windows 11 PC need it?

No. IIS and IIS 6 compatibility features are optional, and Windows editions differ. A computer that never uses IIS administration may not contain this file.

Is adsiis.dll an Exchange file?

Exchange-era setup and administration can require IIS 6 compatibility components, so Exchange may be the application exposing the error. The DLL itself belongs to the Windows IIS provider rather than being an Exchange-only file.

Should I register it with regsvr32?

Generally no. regsvr32 is a registration utility, not a Windows system-file repair tool. Use DISM, SFC, and IIS feature installation instead.

What if the file is present but still will not load?

Repair Windows, verify the IIS compatibility features, identify the failing process and architecture, and investigate missing dependencies. A present file does not prove that its dependencies or surrounding IIS configuration are healthy.

Should I install Visual C++ Redistributables?

Not as a first-line response. adsiis.dll is not a Visual C++ runtime DLL. Install or repair IIS and Windows components first.

What information should I provide to an administrator?

Record the exact error text, Windows version and edition, whether IIS is installed, the failing executable, the DLL path, whether IIS 6 compatibility is enabled, and whether the problem followed an update, role change, antivirus quarantine, or disk issue. That information distinguishes a missing feature from component corruption, dependency failure, and filesystem damage.

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