Mirror or extend your Mac's screen on a monitor or projector

Why it happens

When you plug in a second screen, your Mac usually treats it as extra desk space, so it may show only your wallpaper while your windows stay on the laptop. That's extended mode. Mirroring copies your main screen instead, which is what you want for most presentations and TVs.

How to fix it

1. Connect the monitor, TV or projector and make sure it shows something, even if it's only your wallpaper.

2. Open Apple menu > System Settings and click Displays. Each connected screen appears as a picture at the top. Click the one you want to change.

3. Open the Use as pop-up. Choose Mirror for, followed by your Mac's screen name, to show the same picture on both. Choose Extended display to use the second screen as extra space.

   Displays›Use as

4. For a quicker switch next time, press Command and the Brightness Down key together. On an Apple keyboard that's the F1 key, so Command-F1 does the same. Press it again to switch back.

Still not fixed?

1. If you're extending and the mouse goes off the wrong edge, click Arrange… in Displays and drag the screen pictures so they match where the screens sit on your desk.

   Displays›Arrange…

2. If the Dock and menu bar are on the wrong screen, open Displays, pick the screen you want them on, then choose Main display from Use as.

   Displays›Use as›Main display

3. If a mirrored picture looks stretched or blurry, select the screen in Displays and try another Resolution. Mirroring has to share one size between both screens.

   Displays›Resolution

4. If the second screen isn't listed at all, unplug it and plug it back in, try a different cable or adapter, and try another port on the Mac.

5. If no cable, port or adapter gives you a picture, and the screen works with other devices, contact Apple Support or a repair shop. The Mac's port may have a hardware fault.