Client Access License - Per-user Vs. Per-device

Per-user Vs. Per-device

CALs apply to either a "device" (as defined in the license agreement) or a "user". A business is free to choose either mode. In Per-User mode, a CAL is purchased to allow one user to connect to the server software. Any user can connect, but only one user may use a given CAL at any given time. Any number of CALs can be purchased to allow five, five hundred, or any number of users to simultaneously connect to the server. Any number of devices may connect to the server software, but only a set number of users can connect to it at once.

Per-device mode operates in much the same way, but limits connections made by devices, rather than users. One CAL enables one device to connect to and use the server software, regardless of how many users are connecting.

Although User and Device CALs are currently the same price, they may not be used interchangeably, and cannot be switched without buying new CALs. The price of User CALs is due to increase from December 2012 (in the UK), although the device CAL remains the same.

Much more in-depth information can be found on Microsoft's CAL Guide website.