Window Server Standard Hyper-V licensing

Windows Server Standard, when properly licensed for the cores of the physical host upon which it is installed, includes virtualization rights for up to two Windows Server OSEs (operating system environments) running on the same host server. This includes full Hyper-V VMs or Windows Server Containers running in Hyper-V Isolation. Linux Server VMs do not count against this limit, and require only licensing from their respective vendor (if it is a commercial Linux distribution).

This is part of why Hyper-V Server (which is not being updated past Hyper-V Server 2019) was popular among shops that also ran Linux VMs. Hyper-V Server includes no Windows Server virtualization rights, but can run Linux VMs without additional licensing. Similarly, Azure Stack HCI does not include Windows Server virtualization rights, and any Windows Server OSEs must be licensed separately (through application of Windows Server licenses, or the in-preview Windows Server license subscription program).

In most cases, when running more than two Windows Server VMs on a host, it's advantageous to license Windows Server Datacenter instead of Standard as Datacenter includes rights for unlimited OSEs.