How To Add A Second Monitor To An All-In-One PC

To add a second monitor to an all-in-one PC, first locate a video output port on the back or side of the all-in-one, then connect the external monitor using the appropriate cable. This lets you extend your desktop across both screens, turning your all-in-one into a powerful dual-monitor workstation for increased productivity.

Check your all-in-one PC for a video output port to add a second monitor

All-in-one PCs require an available video output port to connect a second monitor. Look on the back or side of your all-in-one for ports labeled HDMI, DisplayPort, or USB-C. A USB-C port may support DisplayPort Alternate Mode or Thunderbolt, both of which can drive an external display. If your all-in-one lacks any of these ports, you cannot directly add a second monitor without using a USB-to-video adapter or a docking station, though those solutions may have performance limitations. Once connected, you can arrange your workspace with split screen on laptop and monitor to keep reference material open while you work. If you lack the necessary ports entirely, you might instead make my all-in-one PC a screen only for laptop to repurpose its built-in display.

Identifying the essential HDMI, DisplayPort, or USB-C port on the AIO that makes a dual-monitor setup possible is the critical first step. Without it, the external monitor will have no way to receive a video signal from the computer.

Gather the right cable or adapter for your second monitor

Matching the AIO's output port to the external monitor's input port, including when an adapter or specific cable like USB-C to HDMI is needed, ensures the physical connection works. If both devices share the same port type, for example, HDMI on both, a standard HDMI cable is all you need. If the ports differ, such as a DisplayPort on the all-in-one and HDMI on the monitor, use a DisplayPort-to-HDMI cable or a DisplayPort-to-HDMI adapter. For a USB-C port on the all-in-one that supports video output, a USB-C to HDMI cable or a USB-C to DisplayPort cable will work.

Connect the second monitor to your all-in-one PC

1. Power off both the all-in-one PC and the second monitor.
2. Plug one end of the video cable into the video output port on the all-in-one PC.
3. Plug the other end of the video cable into the video input port on the second monitor.
4. Connect the power cable to the second monitor and plug it into a power outlet.
5. Power on the all-in-one PC first and wait for it to fully boot.
6. Power on the second monitor.

The physical step-by-step: powering off both devices, plugging in the video cable and power, then powering on the AIO first and the monitor second reduces the chance of detection issues. After both are on, the operating system should automatically detect the new display.

Configure Windows display settings for dual monitors

1. Right-click any empty area of the desktop and select "Display settings."
2. In the Display settings window, scroll to the "Multiple displays" section.
3. Open the dropdown menu and select "Extend these displays" to use both screens as one large workspace.
4. Click the "Identify" button to see which number corresponds to which display on your screen.
5. Click and drag the numbered display boxes to match their physical arrangement on your desk.

Right-clicking the desktop, opening Display settings, selecting 'Extend these displays', using Identify, and dragging the display boxes to match physical arrangement gives you full control over how your workspace is organized. You can also set different scaling percentages for each monitor by selecting the individual monitor in Display settings and adjusting the "Scale" option.

Configure macOS display settings for dual monitors

1. Connect the external display to your Mac.
2. Click "Displays" in the sidebar.
3. Click the "Arrange" button to view the display layout.
4. Drag the displays to match their physical positions on your desk.
5. To set the primary display, drag the small slim white menu bar to the desired display within the Arrange view.

Going to System Settings > Displays, clicking Arrange, dragging displays to match physical layout, and moving the menu bar to set the primary display ensures your Mac treats the correct screen as the main one. Note that Apple iMacs with two USB-C ports can connect up to one external 6K display, while four-port models can support up to two external 6K displays. The number of external displays a Mac can support depends on the specific Mac model, as well as the resolution and refresh rate of each display.

Troubleshoot a second monitor that won't display

If the second monitor remains blank after connection, start by checking cable connections and input source on the monitor itself. Ensure the monitor is set to the correct input (HDMI, DisplayPort, etc.). If the cable is secure and the input is correct, updating graphics drivers from the manufacturer's website often resolves detection problems. Outdated drivers can cause display issues, so visit your PC manufacturer's site for the latest versions. As a fallback, wireless display options like Miracast (for Windows) or AirPlay (for macOS) can be used to mirror or extend displays wirelessly if supported by the devices. This provides a backup method when a wired connection fails.