How to Perform an In-Place Upgrade to Windows Server 2025

Open an elevated PowerShell prompt and record your current version and edition. A direct in-place upgrade to Windows Server 2025 is supported from Windows Server 2012 R2, 2016, 2019, or 2022 on nonclustered systems. Confirm three things: your source is on that list; your install type matches (Server Core stays Core, Desktop Experience stays Desktop - you cannot switch); and your target edition is the same or a permitted higher one (Standard can move to Datacenter or Datacenter: Azure Edition, but Datacenter cannot be downgraded to Standard). Make sure you have a valid Windows Server 2025 product key or activation method for that edition.

Domain controllers: do not in-place upgrade AD DS servers - build and promote a clean 2025 DC instead. Clusters: use a Cluster OS rolling upgrade, which advances only one version at a time.

Take a full backup of the OS, applications, and data using Windows Server Backup or your partner backup solution, and for virtual machines take a snapshot/checkpoint. Then perform a restore test to confirm the backup is actually recoverable - an untested backup is not a rollback plan. Next, collect diagnostics and store them off the server, and export your installed roles and features so you can compare after the upgrade:

Get-ComputerInfo -Property WindowsBuildLabEx,WindowsEditionID | Out-File .\computerinfo.txt
systeminfo.exe | Out-File .\systeminfo.txt
ipconfig /all | Out-File .\ipconfig.txt
Get-WindowsFeature | Where-Object InstallState -eq 'Installed' | Export-Csv .\installed-features.csv -NoTypeInformation

Copy computerinfo.txt, systeminfo.txt, ipconfig.txt, and installed-features.csv to a USB drive or network share. Confirm at least ~32 GB free on the system drive - insufficient space is the most common cause of upgrade failure.

Disable NIC Teaming before the upgrade - it is a documented prerequisite and a common cause of setup failures. Then pause or stop third-party backup, antivirus, and monitoring agents per each vendor's guidance, since they can interfere with the offline install phase; re-enable them afterward. On virtual machines, a stale virtual NIC or backup-agent filter driver is a frequent culprit behind mid-upgrade failures.

Do not try to stop Microsoft Defender with Stop-Service WinDefend - it is tamper-protected, the command fails, and Defender does not need to be stopped for the upgrade. Only third-party security agents may need pausing.

Mount the non-evaluation Windows Server 2025 ISO (in Hyper-V/VMware, attach it to the VM; on physical hardware, mount the ISO or insert the USB/DVD). Note the drive letter, then list the editions inside the image so you know which index matches your install type and target edition:

Mount-DiskImage -ImagePath 'C:\ISOs\WindowsServer2025.iso'
dism /Get-WimInfo /WimFile:D:\sources\install.wim

Replace D: with the mounted drive letter. The index numbers are specific to your ISO, so read them from this output rather than assuming a fixed order.

You do not have to use /imageindex at all - when you run setup interactively, Setup shows a matching edition to select. Note the index only if you plan the unattended command in a later step.

From the mounted media, run Windows Setup in scan-only mode to check for compatibility problems without starting the upgrade:

D:\setup.exe /Auto Upgrade /Compat ScanOnly /EULA accept

Review any warnings or blocks - typically incompatible applications, unsupported drivers, or roles that need attention. Resolve critical items before proceeding; note non-critical warnings so you can address them afterward.

The scan is read-only and does not change the server. If it flags an application, uninstall or update it before the real upgrade rather than forcing past it.

From the mounted media, run setup.exe and follow the wizard:

1. If prompted about downloading updates, choose your preference - Change how Setup downloads updates and pick Not right now if you are troubleshooting reliability, otherwise leave the default.
2. Enter your Windows Server 2025 product key when prompted.
3. Select the edition that matches your current install (same or a permitted higher edition).
4. Review and accept the license terms.
5. On the choice of what to keep, select Keep files, settings, and apps - this is what makes it an in-place upgrade.
6. Click Install.

The server copies files, installs features and drivers, and restarts several times automatically. Do not interrupt it or power off during the upgrade.

If you do not see Keep files, settings, and apps (older builds may word it *Keep files and apps* or *Install Windows and keep files, settings, and applications*), it usually signals an edition mismatch, a Core/Desktop mismatch, or evaluation media - go back and verify your media and edition.

From an elevated PowerShell prompt on the mounted media, run Setup with unattended switches. The simplest reliable form lets Setup auto-match your current edition:

.\setup.exe /auto upgrade /dynamicupdate disable /eula accept

If your ISO contains multiple editions and you need to pin one, add /imageindex <n> using the index you read from DISM, and add /quiet /compat ignorewarning for a fully silent run. Monitor progress from another window:

Get-Content C:\Windows\Panther\setupact.log -Wait -Tail 10

Use /compat ignorewarning only after you have reviewed the scan results and judged the warnings acceptable - it suppresses the very prompts that would otherwise stop a bad upgrade. /imageindex values are ISO-specific; the wrong index (e.g. Core when you run Desktop Experience) will block the upgrade.

The Windows Update path applies only to Windows Server 2019 or 2022 (non-Azure) and needs two things first: the required cumulative update installed (KB5078766 or later for 2022, KB5078752 or later for 2019), and an opt-in registry value. Add the opt-in key from an elevated prompt, then check Windows Update:

New-Item -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AllowWindowsServerFeatureUpdate' -Force
New-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AllowWindowsServerFeatureUpdate' -Name 'AllowWindowsServerFeatureUpdate' -PropertyType DWord -Value 1 -Force

Then open Settings > Windows Update and look for the Windows Server 2025 feature update offer.

The same backup, licensing, and role prerequisites apply. This path is not available for 2012 R2 or 2016 (use media) or for Azure VMs (use the Azure in-place upgrade method).

Log in and confirm the version, then reactivate and validate. Check activation with slmgr /xpr; if needed, install your key and activate:

slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
slmgr /ato

Install the latest cumulative updates, re-enable the third-party agents you paused and re-create NIC Teaming if you used it, then compare installed roles and features against the CSV you exported earlier and test your key applications. For KMS environments, ensure the KMS host already has a Windows Server 2025 key loaded.

Wait until the server has been stable for a while before running heavy cleanup such as Dism /Online /Cleanup-Image /StartComponentCleanup /ResetBase - /ResetBase removes the ability to uninstall the superseded components.