There are a few different ways to loop a video on a Mac. One way is to use the QuickTime Player application. To do this, open the QuickTime Player application and then open the video file that you want to loop. Once the video is open, click on the "View" menu and then select "Loop." Alternatively, you can use the VLC Media Player application to loop a video. To do this, open the VLC Media Player application and then open the video file that you want to loop. Once the video is open, click on the "Playback" menu and then select "Loop."