Rotate your external monitor to portrait (or fix a sideways screen)

Why it happens

Your Mac doesn't know how a monitor is physically placed, so it keeps drawing a landscape picture until you tell it otherwise. If you turn a monitor on its side, the picture looks sideways until the Rotation setting matches. A wrong Rotation choice is also why a screen can suddenly look upside down.

How to fix it

1. Click the Apple menu, choose System Settings, then click Displays in the sidebar.

2. If you have more than one screen, click the monitor you want to rotate at the top of the page.

3. Open the Rotation pop-up menu and pick an angle. 90° and 270° are the two portrait directions, 180° is upside down, and Standard is normal landscape.

   Displays›Rotation

4. The picture turns to match. If your Mac asks you to confirm, confirm the change so it stays. If it's facing the wrong way, choose the other portrait angle.

Still not fixed?

1. If there's no Rotation menu for your monitor, the connection may not support it. Some docks, adapters and wireless displays don't offer rotation, so try connecting the monitor straight to your Mac with a cable.

2. After rotating, the pointer may cross to the wrong edge of the screen. Click Arrange… in Displays and drag the screens to match your desk.

   Displays›Arrange…

3. If the rotation keeps changing back after sleep or reconnecting, check the monitor's own on-screen menu for an auto-rotate setting, and install any macOS update waiting in Software Update.

   General›Software Update

4. If the picture flickers, has stripes or is garbled in any rotation, try another cable or port. If it happens with every cable, contact the monitor's maker or Apple Support, since that points to a hardware problem.