The tiers
480p is the data-saver tier and looks fine on a phone; 720p and 1080p are both HD, 1080p the full frame, and the difference shows on a television and disappears on a phone; 4K is the top tier of the global services for films finished for the cinema. The HD label on every card says the title plays in high definition on the services in the Watch now list, and the service decides the tier from the master, your plan and the screen.
Data
HD needs about five megabits a second and uses one to three gigabytes an hour; a film in HD is three to four gigabytes and about one at 480p; a season of a series is six to eight in HD. Choose 480p on mobile data and 1080p on Wi-Fi, and the downloads page explains how to bring a season down the night before.
When it buffers
Drop the tier one step in the service's player and it settles; a television at the far end of the house on Wi-Fi is the usual cause, and the devices page covers the rest.
