Software for Mac to view full screen

I am looking for a free or inexpensive software to allow viewing in a full screen, not just a window, a real time video on my Mac.
The image is coming in from the Intensity Shuttle for USB 3.0.
Sorry I am not a good searcher as this must be answered already but could not find it. Thanks.

OBS Studio is free and allows you to do full screen.

We use MITTI, not free, but inexpensive.

Thanks so much ... tried OBS and it worked well