Quick answer: Install the edition that matches your key (Standard or Datacenter), then run slmgr /ipk YOUR-KEY and slmgr /ato in an administrator Command Prompt. If you installed from Microsoft's evaluation ISO, convert it first with DISM /Set-Edition (Step 4), then activate.
This guide covers Windows Server 2025 Standard, Windows Server 2025 Datacenter, Windows Server 2025 Essentials, the 2022 and 2019 editions, and core add-on licences. For CALs and Remote Desktop licences, see our CAL and RDS CAL guide.
Before you start
- Count your physical cores. Standard and Datacenter are licensed per core, with a minimum of 16 cores per server. Core add-on keys extend an existing licence; you don't enter them in Windows, you keep them with your licence records.
- Choose the installation option. Pick Desktop Experience if you want the normal Windows interface; Server Core has no desktop.
- Hardware minimums (2025): 1.4 GHz 64-bit CPU, 2 GB RAM (4 GB recommended with Desktop Experience), 32 GB disk, TPM 2.0 and Secure Boot for some features.
Step 1: Get the installation ISO
| Source | Notes |
|---|---|
| Download link in your order email | Full installation media. Activate directly with your key (Step 3). |
| Microsoft Evaluation Center (2025, 2022, 2019) | Official evaluation ISO. Works fine, but must be converted to a full edition before your key is accepted (Step 4). |
Step 2: Install Windows Server
- Write the ISO to a USB stick (for example with Rufus) or mount it in Hyper-V, VMware or your server's remote console.
- Boot from it and select Install.
- Choose the edition that matches your key: Windows Server Standard (Desktop Experience) or Datacenter (Desktop Experience).
- Choose Custom: Install Windows Server only, select the disk and finish setup.
- Set the local Administrator password and sign in.
Step 3: Activate Windows Server
Using Settings: open Settings → System → Activation (on 2019 and 2022: Settings → Update & Security → Activation), select Change product key and enter your key. You can also click the Product ID link in Server Manager → Local Server.
Using the command line (works on Server Core too). Open Command Prompt as administrator:
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXXslmgr /atoslmgr /dlv
The last command shows the edition and confirms "License Status: Licensed".
Step 4: Convert an evaluation installation
Evaluation editions (ServerStandardEval, ServerDatacenterEval) reject retail and volume keys until you convert them. You don't need to reinstall:
- Open PowerShell or Command Prompt as administrator and check the edition:
DISM /online /Get-CurrentEdition - List the editions you can switch to:
DISM /online /Get-TargetEditions - Convert using Microsoft's public generic setup key for your version and edition:
DISM /online /Set-Edition:ServerStandard /ProductKey:GENERIC-KEY /AcceptEula
UseServerDatacenterfor Datacenter. - Restart when prompted. The server may restart twice.
- Enter your own key and activate:
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXXthenslmgr /ato
Important: convert before the evaluation period expires, and note that Microsoft doesn't support converting a server that is already a domain controller. Convert first, then promote it.
Troubleshooting
| Error or symptom | Fix |
|---|---|
| "The product key you entered didn't work" | You're on an evaluation edition or the wrong edition. Run DISM /online /Get-CurrentEdition and convert if needed. |
| 0xC004F069 or edition mismatch | A Datacenter key on Standard (or the reverse). Convert to the edition that matches your key. |
| Activation server can't be reached | Check DNS and outbound internet access, or run slui 4 for phone activation. |
| Set-Edition fails | Make sure you used the generic key for the same Windows Server version, and that the server isn't a domain controller. |
Still stuck? Reply to your order email with the output of slmgr /dlv and we'll help.
Frequently asked questions
Do I need CALs?
Yes, for Standard and Datacenter. Every user or device that accesses the server needs a Windows Server CAL, and Remote Desktop users need RDS CALs as well. See our CAL guide. Essentials doesn't need CALs (up to 25 users and 50 devices).
How many virtual machines can I run?
Standard allows 2 virtual machines when all physical cores are licensed. Datacenter allows unlimited VMs.
Where do I enter a core add-on key?
Nowhere in Windows. Core add-on licences cover extra physical cores on a server you have already activated; keep them with your licence records for audits.
Useful links
| Link | What it's for |
|---|---|
| Windows Server 2025 Evaluation Center | Official ISO download |
| Generic setup keys (Microsoft) | Converting evaluation editions |
| Windows Server 2025 Standard 16-core | Buy a server licence |
| CAL and RDS CAL guide | Licensing users and Remote Desktop |