The right shape before the right pixelsA better fit.
A better everyday view.
Use your display’s actual resolution when you have it. These common canvas sizes are starting points, not a promise that every phone or monitor uses the same dimensions.
Match the aspect ratio first.
Width divided by height describes the shape of a canvas. A tall phone, a square image and a wide desktop need different compositions. Stretching a finished image can distort a subject; cropping can remove important edges. Starting with a similar shape usually gives you more useful pixels to work with.
Leave room for the interface.
Phones place clocks and widgets over a wallpaper, while desktops add icons, windows and taskbars. Leave the busiest interface areas visually quieter. If your screen pans or zooms a wallpaper, keep extra space around the subject and inspect the crop on the actual device.
Separate detail from dimensions.
A 3840 × 2160 download has a 4K-sized canvas. If it comes from a smaller original, resizing does not supply the detail of a native 4K generation. Keep the original, compare exports at actual viewing size and choose PNG when exact black values or flat color are important.