Client Server License / Client Access License (CAL)

The Client Access License (CAL) is a form of license management that can be found primarily in Microsoft products. It is required in client-server environments. If you want to access a server, you must not only purchase licenses for the server and the client itself, but also purchase CALs that authorize the server to accept client connections.

There are two options for the form of licensing: The first refers to individual workstations, which allows the workstation to connect to any number of servers in the network. It is the more cost-effective variant if there are several servers in the network. The second licensing method refers to the server, so that any number of clients can be active in the network, but only a limited number can connect to the respective server. This is useful if there is only one server in the network. When purchasing Microsoft server products, a small number of client access licenses are often included.