As many as you want. In fact we don't ask you to "register" any devices. NoMachine Network does not place limits on the number of devices you can connect from and which computers you want to connect to. For example, let's say you have installed NoMachine software on all the devices you want to connect from and have published all the computers you want to access on Network. Whatever the total is, it does not matter. You can be logged in to the service with your account on unlimited computers and devices if you wish. What counts is the number of connections you start from one of those devices. How many connections you run from that device depends on the type of Network Subscription you have. It won't be possible to start a second connection from a different device with the same User Id.