Set Up and Arrange an External Display on Your Mac

You’ve connected a second monitor to your Mac and want to set it up the way you actually sit — extended for more space, or mirrored — and put the screens in the right positions.

Why: macOS treats the displays as one connected desktop. By default it extends the desktop, but the arrangement (which screen is left, right, or on top, and which is the main one) often doesn’t match your physical setup until you drag the displays into place.

Fix 1: Connect the display and confirm it’s seen

1. Plug the monitor into your Mac (USB-C/Thunderbolt, HDMI, or a compatible adapter) and turn the monitor on.
2. Choose Apple menu > System Settings, then click Displays in the sidebar.
3. Each connected screen appears at the top. Click the second display to select it and adjust its settings.

If the monitor doesn’t appear at all, that’s a detection problem rather than an arrangement one — see our guide on a Mac not detecting an external display.

Fix 2: Choose Extended or Mirrored

1. In Displays, select the external display, then find the Use as pop-up menu.
2. Choose Extended display to spread your desktop across both screens (more room), or Mirror for [display] to show the same thing on both.
3. With more than two displays, you can mirror some and extend others — set each display’s Use as option independently.

Extended gives you more workspace; mirrored is best for presentations where everyone should see the same screen.

Fix 3: Arrange the displays to match your desk

1. In Displays, click Arrange (it appears when more than one display is connected). You’ll see blue rectangles representing each screen.
2. Drag the rectangles so they sit the way your monitors physically sit — side by side, or one above the other. This controls where the pointer crosses from one screen to the next.
3. To set which screen has the menu bar and Dock, drag the white bar at the top of one rectangle onto the display you want as the main display.
4. Close settings; the layout takes effect immediately.

FAQ

My pointer jumps to the wrong screen edge. The arrangement doesn’t match your desk — drag the display rectangles in Arrange to match the physical layout (Fix 3).

How do I move the menu bar to the other monitor? In Arrange, drag the small white bar onto the display you want as the main one (Fix 3).

Both screens show the same thing and I want more space. You’re mirrored — switch the external display’s Use as to Extended display (Fix 2).

Sources: Apple Support — Connect one or more external displays with your Mac, Apple Support — Extend or mirror your Mac desktop across multiple displays