The Multi-Monitor Mystery
macOS handles multiple monitors very well, but its Dock behavior can sometimes be confusing. By default, the Dock is pinned to the bottom of your primary display. However, if you move your mouse cursor to the bottom edge of a secondary external monitor, the Dock will suddenly vanish from your main screen and teleport to the bottom of the external display. While Apple designed this to make the Dock accessible from any screen without having to drag your mouse all the way back to the primary monitor, many users find this “auto-hiding” and teleporting behavior unpredictable, preferring the Dock to remain statically pinned to one specific screen.
Pinning the Dock to One Screen
To establish a consistent workspace and stop macOS from automatically hiding the Dock on your main display and moving it to your external displays, you must adjust your Mission Control settings regarding how spaces are handled.
Open System Settings (or System Preferences on older versions) by clicking the Apple logo in the top-left corner. Scroll down the left-hand sidebar and click on Desktop & Dock. Scroll down the main window until you reach the “Mission Control” section. Look for the toggle switch labeled Displays have separate Spaces. By default, this is turned on, which enables the Dock to move between screens. Click the toggle to turn it Off. You will be prompted to log out of your Mac and log back in for the changes to take effect. Once you log back in, your external monitors will act as one continuous extension of your primary screen, and the Dock will be permanently locked to the bottom of your main display.