djay Pro for Mac offers the ability to play your video mix on an external display. You can either connect a monitor via HDMI or through an AppleTV. Once connected, follow these instructions to set up your display with djay.
Setting up your display
First, make sure that the secondary screen is connected to your computer through the macOS Settings. To do this, open the "Displays" settings, and you should then see the two displays next to each other:
If the two displays appear as overlapping in the Displays settings window, it means that you have "Screen Mirroring" active. You'll need to disable this setting by right-clicking on the displays then selecting "Stop Mirroring" in the pop-up options:
Please note that using Apple's Universal Control feature, you can also connect an iPad as your secondary display.
Lastly, in djay's Video mode, click on the icon to the top-right of your master video screen. Here, you can select the display to which you wish to send your master video mix. Select the desired screen in the drop-down menu, then click "Show":