Saving a title is not downloading the film
The heart button keeps a title in My List. It does not store the movie on your phone. A list backup holds title choices and manual episode checkpoints, so it stays small and easy to move.
For a journey without a connection
Open your chosen viewing service and look for its offline option. Confirm that the specific film or episode can be downloaded on your device and account. A browser offer and a mobile-app offer can have different controls.
Check before leaving
Make sure the download finishes, open it once, and inspect the audio and subtitle choices. Expiry rules, available storage and the number of devices depend on the service you use. Saving a web bookmark is not a substitute for that check.