Most carriers throttle SD video to movie hd app relieve network congestion, so it's always a good idea to check your carrier's speed limit before renting a video. You can also rent or buy movies in both standard and high definition formats to save money on bandwidth costs.

If you want to watch your purchases on a big screen, you'll need an HDTV or compatible 4K TV. But if you're going to be using your iPhone or iPad on a smaller screen like an old tube TV, SD is still a great choice because it doesn't take up as much space.