I have a requirement to be able to see what is being displayed on the second monitor connected to a macbook on the primary display. I can't use mirroring for this because I will doing something different on the primary display. I need to be able to see the second monitor display in a window.
I am going to be connected to a large display on stage and (potentially) won't be able to see it.
Does anyone know if there are any apps that will allow this specific functionality?
Best Answer
There are two apps I've seen that claim to give a picture-in-picture type view of the secondary display: Displays and Side Mirror. Neither is free, but such is life.
Alternately, MacOS (since High Sierra, I think) allows you to arrange multiple displays in complex ways. You could add a third display (or an iPad, if your system supports SideCar), and mirror that to your secondary display, leaving your primary display in extended desktop mode with the secondary. Apple's instructions are here.