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Upload at 2560 × 1440, but design inside the central 1546 × 423. That centre rectangle is the only part guaranteed to show on every device — a TV shows the whole image, a phone shows almost nothing but the middle.

This is the most aggressively cropped placement on any platform, and the reason is that the same file has to serve a television and a phone. A TV displays the full 2560 × 1440; a desktop browser shows a 2560 × 423 letterbox slice; a phone shows only the 1546 × 423 centre. Anything you actually need read — a channel name, a schedule, a handle — has to be inside that centre box, and the rest is decoration that most of your audience will never see. It is worth checking the result on a phone, because designing at full size on a large monitor makes the crop feel much less severe than it is.