Windows Security app is missing from Windows Server 2025 Standard installation

[oldsports]

I downloaded Windows Server 2025 Eval to test it out prior to making the commitment to convert my 2016 Essentials server ahead of the January 2027 deadline. I performed a clean-install and tested it out - everything I wanted to do worked fine, so I decided to convert.

Instead of upgrading, I decided to clean-install Windows Server 2025 Standard, re-create the users/devices from my 2016E server, and port over the data; I have a small number of users/devices so it seemed like the cleanest option. I installed 2025 Standard using the installation disk that came with my license. The installation seemed to go fine, but when I checked out the security set-up Windows Security was not installed. In fact, the software for the app was nowhere to be found in the installation - Powershell commands to install it gave errors saying that it could not be found. I even searched with the Search Tool - no luck.

I was under the impression that Windows Security came standard in 2025 Standard. The Eval version had it (that was one of the things I checked). Is it possible I had a bad install? Did I miss answering an installation question about it (I don't recall that when I installed the Eval version)? Can Windows Security be installed as a standalone app? If so, where would I get the installation package? Other ideas? I can do the reinstall, but I don't want to make the same mistake again if I missed something. I guess that, worse case, I could use the Eval version to install and convert it to Standard.

Thanks!

 

[ChatGPT]

Hi oldsports,
Yes — Windows Server 2025 Standard should include Microsoft Defender Antivirus, and on a Desktop Experience install you should normally have the Defender/Windows Security UI available as well. Microsoft’s current Server guidance says Defender Antivirus is installed by default on Windows Server 2016 and later, and if needed can be reinstalled from Add Roles and Features or PowerShell.
My first suspicion is not a bad install, but one of these:

1. You installed Server Core instead of Standard with Desktop Experience.
2. The Defender feature was removed/missing from that particular install image.
3. Defender is installed, but only the GUI/Windows Security front-end is missing or broken.
4. The retail/OEM media is older or customized differently than the Evaluation ISO.

Check what was actually installed​

Run this in PowerShell as Administrator:

Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion' |
Select-Object ProductName, EditionID, InstallationType, DisplayVersion, CurrentBuild

Expected result:
InstallationType : Server
If it says:
InstallationType : Server Core
then that is the issue. You cannot convert Server Core to Desktop Experience after installation. You would need to reinstall and choose:
Windows Server 2025 Standard with Desktop Experience
Microsoft documents that the setup list includes both Windows Server Standard and Windows Server Standard with Desktop Experience, and the one without Desktop Experience is the Core option.

Check whether Defender exists as a Windows feature​

Run:
Get-WindowsFeature *Defender*
Also check services/status:

Get-Service WinDefend, mpssvc -ErrorAction SilentlyContinue
Get-MpComputerStatus

If Windows-Defender shows as Available, install/reinstall it:
Install-WindowsFeature -Name Windows-Defender -IncludeAllSubFeature -Restart
After reboot, verify:

Get-Service WinDefend
Get-MpComputerStatus

Expected outcome:

WinDefend : Running
AMServiceEnabled : True
AntivirusEnabled : True
RealTimeProtectionEnabled : True

If the Defender GUI is the only missing piece​

Open Server Manager:

1. Go to Manage.
2. Select Add Roles and Features.
3. Proceed to Features.
4. Look under Windows Defender Features.
5. Select Microsoft Defender Antivirus and, if present, GUI for Windows Defender.
6. Finish the wizard and reboot if prompted.

Microsoft’s Server Defender article specifically mentions selecting Microsoft Defender Antivirus and the GUI for Windows Defender from the Features page.

Check the Windows Security app package​

On Desktop Experience, also try:
Get-AppxPackage -AllUsers Microsoft.SecHealthUI
If it exists but is broken, try resetting it:
Get-AppxPackage -AllUsers Microsoft.SecHealthUI | Reset-AppxPackage
If that errors, try re-registering it:

Get-AppxPackage -AllUsers Microsoft.SecHealthUI | ForEach-Object {
    Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppxManifest.xml"
}

If Microsoft.SecHealthUI is completely absent and Get-WindowsFeature *Defender* does not show a usable Defender feature, I would treat the install media as suspect.

If the feature source is missing​

If PowerShell says the feature cannot be found or the source files are missing, repair the component store from known-good Server 2025 media.

1. Mount the ISO or insert the install media.
2. Find the image index:

dism /Get-WimInfo /WimFile:D:\sources\install.wim
If the file is install.esd, use:
dism /Get-WimInfo /WimFile:D:\sources\install.esd

1. Use the index for Windows Server 2025 Standard with Desktop Experience.
2. Repair the component store:

DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:D:\sources\install.wim:<index> /LimitAccess

1. Then run:

Install-WindowsFeature -Name Windows-Defender -IncludeAllSubFeature -Restart
Replace D: and <index> with the correct drive letter and image index.

Can Windows Security be installed standalone?​

Short answer: I would not try to install it as a standalone app.
On Windows Server, Defender/Windows Security should come from the Windows image/component store or Server Manager features. Do not download random SecHealthUI, Defender, or Windows Security app packages from third-party sites. That is risky and may leave you with an unsupported or compromised security component.

About using the Evaluation ISO and converting it​

Your fallback idea is reasonable, with one caution.
You can install Windows Server 2025 Standard Evaluation with Desktop Experience and convert it to retail Standard using DISM, provided the target edition is listed:

DISM /online /Get-CurrentEdition
DISM /online /Get-TargetEditions
DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula

Important: Microsoft notes that an evaluation server that is already an Active Directory domain controller should not be converted directly to retail. Since you are rebuilding from 2016 Essentials, I would convert/activate before promoting it to a DC or migrating production roles.

My recommendation​

1. First confirm whether you installed Desktop Experience.
2. If it was Server Core, reinstall and choose Windows Server 2025 Standard with Desktop Experience.
3. If it was Desktop Experience but Defender is missing, try Install-WindowsFeature -Name Windows-Defender -IncludeAllSubFeature.
4. If the feature is not even available, use the latest Microsoft Server 2025 ISO rather than the supplied disk.
5. Before rebuilding production services, make a bare-metal backup of the old 2016 Essentials server and export/copy your data separately.

Given your Eval install had Windows Security and the licensed-media install did not, I’d lean toward media/install-option difference, not something you “missed” during setup.