Windows Server licences are delivered by email within seconds, with the product key and a link to Microsoft’s official evaluation ISO — the same media used for licensed installs. This guide covers installation, activation and the two licensing questions that catch people out.

Understand the licensing before you install

Two things are worth being clear on. First, Windows Server is licensed by physical core, with a minimum of 16 cores per server and 8 per processor. Count physical cores, not logical threads. Second, Client Access Licences are separate: the server licence covers the operating system on the hardware, while CALs cover the right of users or devices to connect to it. CALs are not included with the key.

Step 1 — Download the ISO

Use the Microsoft link in your delivery email. Microsoft distributes Server as an evaluation ISO which converts to a fully licensed installation once your key is applied — this is the normal, supported route and not a workaround. Write the ISO to a USB drive of 8 GB or more, or mount it directly if you are installing into a virtual machine.

Step 2 — Choose Server Core or Desktop Experience

Setup offers both, from the same ISO and the same key. Server Core has no graphical shell: a smaller attack surface, fewer patches and lower resource use, managed remotely through Windows Admin Center or PowerShell. Desktop Experience gives the familiar Windows interface on the server itself. Choose Core for infrastructure roles, Desktop Experience if someone needs to log in locally. You cannot switch between them later without reinstalling, so decide now.

Step 3 — Choose the correct edition

Standard and Datacenter install from the same media. The practical difference is virtualisation: Standard permits a limited number of virtual instances on the licensed hardware, while Datacenter allows unlimited virtualisation. If you are running more than a couple of guests, Datacenter is usually the cheaper answer overall. Install the edition your key is for.

Step 4 — Activate

If the machine is already running as an evaluation, convert it using DISM from an elevated command prompt, substituting your own key. Otherwise open Settings → System → Activation and enter the key there. Confirm with slmgr /dli in an elevated prompt, which reports the licence status directly.

If activation fails

Check the edition first — a Standard key will not activate a Datacenter installation. Servers are also frequently isolated from the internet, in which case telephone activation is the correct route, and our free Confirmation ID service handles it. Send us your order number and the exact error code and we will work through it with you; every order is covered for 180 days.

Browse our Windows Server product keys, including Server 2022.