To use Google Chromecast with Prime Video, you need the most recent version of the Prime Video app for either iOS or Android.

1. From the Prime Video app, select the Cast icon.
2. Select the Chromecast device that you wish to use.
   Your iOS or Android device must be connected to the same Wi-Fi network as your Chromecast. Please ensure that your Chromecast, whether standalone or built-in to another device, is up to date. Also ensure that your Prime Video app and iOS or Android device are also up to date. If you are running an Android device, ensure that Google Play Services are also up to date. The Prime Video app on Fire Tablets are not able to use Chromecast.
3. Select a title you wish to watch. This title will then shown on the display that the Chromecast is connected to.
   If you wish to change subtitle settings on Chromecast, on iOS devices, you must stop Casting to that device. Then select Settings > Accessibility > Subtitles and Captioning > Style and select a style for your subtitles. On Android devices, while a title is being Casted, tap the three-dot menu on the screen. Select Subtitle styles and toggle on Show captions. You can also select Caption size and style options from that menu.