The label
Every card carries HD, and it means the title exists in a real high-definition release and the services on the Watch now list carry it that way. No cinema recordings, ever; a film arrives here when it reaches a service in HD, a few weeks after the cinema for most and a little longer for the largest.
720p, 1080p, 4K
720p and 1080p are both HD; 1080p is the full frame, and the difference shows on a television, not a phone. Films and series from the 2020s were finished at or near 4K and play there on a 4K screen with the plan that includes it, often with HDR, which is usually the more visible upgrade. A film from 2004 was usually finished at 2K; its 4K stream comes from a fresh scan of the film or an upscale. The year on the card is the quickest guide.
Which tier you get
The service decides from the master, your plan and the device: 1080p on any plan on a phone or laptop, 4K on a 4K television on the plan that includes it. Press Watch now and the service's own page names the tier.
Data
HD needs about five megabits a second to play cleanly and 4K about twenty-five. On a data plan, HD uses one to three gigabytes an hour, 4K six to eight. On a metered connection choose HD, or download in the service's app over Wi-Fi first. Buffering: drop the tier one step in the player.