Since you are sharing the entire Mac desktop through Chromecast, the slideshow will display on the TV screen.

Please set the screen size of the slideshow to full screen and you can see the play button to automatically play the images that you selected on the Mac. Now, click on the “ Quick Look” icon from the Finder menu to start the image slideshow without any third-party software. You can open the Finder Window on Mac for the images and videos and select the images you want to display. Now open the photos folder that you want to the slideshow on TV. Whatever on the Mac or Windows Desktop will display on the TV screen.

Now your desktop screen is casting to the TV. Related: How to Stream Local Videos to Chromecast from PC & Mac Start Picture Slide Show from Mac to TV

If you want to stop casting, you can click on “STOP” to stop casting the desktop to Chromecast TV. You may see a confirmation window like below for a short time on chrome browser stating that you are casting Desktop to TV. Once you confirmed, please click on the “ Share” button to start casting. The Chrome browser will confirm to cast the desktop to TV before you proceed. Once you select the desktop to cast, you may need to make sure the streaming device if you have more than one cast supporting device in your home. In this case, you can select the desktop to cast with Chromecast. You can select the tab or the entire desktop to cast.

Now, click on the “ Cast to” to select the casting source.

How to get hdmi from mac to tv