Guides
Everything about Mac wallpapers, briefly.
No filler, no screenshots of screenshots — just the numbers and the steps that work.
How to change the wallpaper on a Mac
System Settings, your own pictures, one wallpaper per display, and the Aerial films macOS keeps to itself.
Mac wallpaper size, screen by screen
The exact pixel size for every current Mac, why the desktop reports half of it, and what one file has to be to cover a whole desk.