Choose quality for the actual movie
A sharp poster is not a video-quality label. Use the viewing edition's listed options when choosing HD, 1080p or 4K. The same title may be offered in different formats, and a display capable of 4K does not make every source a 4K source.
For a smaller screen, a stable HD picture can be more comfortable than a higher setting that pauses repeatedly. For a large television, source detail, compression and the selected display mode become easier to notice.
Auto quality and a changing connection
Where a player provides Auto, it can choose among available picture levels as the connection changes. A temporary soft image may improve once the connection settles. If it keeps stopping, try a lower offered setting and pause other heavy downloads on the same connection.
Full-screen, speed and Picture-in-Picture
Controls differ between viewing services and browsers. Look at the active player's menu for full-screen, playback speed or Picture-in-Picture. Catflix's title page helps you choose what to watch; its Quick look window is a description preview, not a second video player.
A widescreen film can have bars above and below the image without anything being broken. Cropping to fill the television may hide part of the frame. Use the device guide for screen setup and the subtitle guide for caption readability.