Feature tour · 2 of 16
Second monitor
More desk, the same screen, or the only screen
Extend gives the device a screen of its own. Mirror copies one the Mac already has. Alone makes it the only screen there is. More than one device can be doing it at the same time, and how many depends on your Mac.
Extend, for more desk
The device becomes a screen of its own beside the ones you have. Reference on the tablet, work on the Mac.
Mirror, and you pick which screen
Not just the main one. Choose which of the Mac's screens the device copies, and macOS treats the two as one screen, so a window dragged over there comes back where it belongs when you stop.
Alone, for just this one
The only screen; every other one folds into it. Useful on a sofa or a train, where a window opening on a desk in another room is a window you have lost.
Or hand over a single window
A Mac being used as the display can take one window instead of a whole screen. Pick the window and the screen it is given is cut to fit it.
More than one, each doing its own thing
A tablet on the desk extending, a phone on the shelf mirroring, another Mac taking a single window. They run at the same time, and none of them is obliged to match the others. How many run at once depends on your Mac.
A display in System Settings, like any other
Open Displays and it is there beside the screens already on your desk, ready to be arranged, rotated and given a size. Mission Control and Spaces work on it, and windows drag onto it the way they do anywhere else.