Why a server license needs CALs
Microsoft licenses Windows Server in two tiers. The server license, which is core-based, covers the operating system on the hardware. However, it does not permit access by users or devices. Every access requires an additional license, the Client Access License.
This applies to the editions Standard and Datacenter. So anyone running a server for twenty employees needs the server license and an additional twenty CALs, in one variant or the other. Only Windows Server Essentials is exempt from the CAL requirement.
User CAL or Device CAL
The two CAL types cost the same; the difference is purely economic. Anyone with more devices than users is better off with Device CALs. Anyone with more users than devices, with User CALs. Many companies mix both types, depending on the department.
| CAL type | Licenses | Cost-effective when |
|---|---|---|
| User CAL | One user, on any number of devices | Employees use multiple devices, such as a notebook plus a mobile device |
| Device CAL | One device, for any number of users | Several employees share one device, such as in shift operation |