Can I connect two Macs with HDMI?
A Thunderbolt 3 docking station lets you connect your MacBook via one cable to the dock that will have multiple ports, including one or more HDMI, DisplayPort or VGA ports.
Can I use another Mac as a second monitor?
You can use more than one iMac as a display, if each iMac is using a Thunderbolt cable to connect directly to a Thunderbolt port on the other Mac (not the other iMac). Press Command-F2 on the keyboard of the iMac. You should now see the desktop of the other Mac.
Is it possible to connect two Macbooks together?
Connect the two Macs
Attach a Thunderbolt cable between two Macs. Open System Preferences > Network and choose Thunderbolt Bridge in the network interface list on the left hand side of the window.