How Windows Server 2025 Standard is licensed
Core licences, virtual machines and Client Access Licences for a Windows Server 2025 Standard server
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Windows Server 2025 Standard is licensed per physical core, with at least 16 core licences per server. Licensing every core covers two virtual machines, and each user or device that connects to the server also needs a Client Access Licence (CAL). Microsoft positions Standard "for customers with low density or non-virtualized environments", which describes most small office servers.
Core licences
Microsoft's licensing guidance says "all physical cores on the server must be licensed", with a minimum of 8 core licences per physical processor and 16 per server.
| Server hardware | Core licences needed |
|---|---|
| One 8-core processor | 16 |
| One 16-core processor | 16 |
| One 24-core processor | 24 |
| Two 6-core processors | 16 |
| Two 12-core processors | 24 |
The two 6-core processors need 16 because each processor counts as at least 8. Logical processors and hyper-threading don't change the count, which is based on physical cores.
Virtual machines
With every core licensed, "Standard has rights to use two OSEs or two Windows Server containers with Hyper-V isolation". An OSE, or operating system environment, is Microsoft's licensing term for an installation of Windows Server, physical or virtual. The installation on the host itself doesn't use up one of the two, as long as it only runs Hyper-V and manages the virtual machines.
For two more virtual machines, license every core again. A 16-core host licensed twice covers four virtual machines, and three times covers six.
Client Access Licences
Microsoft's rule is "Each user or device that accesses licensed servers requires a Windows Server CAL (Base CAL)." A user CAL covers one person on any number of devices, and a device CAL covers one device, whoever uses it. CALs have to be for Windows Server 2025 or a later version.
Running desktops or apps for users through Remote Desktop Services needs a Remote Desktop Services CAL for each of them as well. Two administrators can connect at the same time for management without one.
What the product key does
A product key only activates the server. The cores, virtual machines and users you're entitled to come from the licences you hold, so keep the order records with the server's documentation.
Our blog's guide to Windows Server 2025 Standard works through the licensing for a small office, including when Datacenter costs less.