. CALs are required by Microsoft licensing for all users or devices that access Windows Server Standard or Windows Server Datacenter. When a customer buys Windows Server Standard or Datacenter they receive a server license that allows them to install the operating system on one computer. A server software license by itself doesn\'t provide the license rights to allow anyone to connect to that computer whether they work for the company or not. Instead each user or device needs a CALKey Product Info . CAL is a Client Access LicenseEvery user or device accessing Windows Server Standard or Datacenter requires a CALThis license allows 5 devices to access Windows Server 2012 2016 or 2019Good for companies that have more devices than users