The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →To connect a second monitor to an all-in-one PC, first confirm that the PC has a video output compatible with an input on the monitor. Connect them with a suitable cable or adapter, then press Windows key + P and choose Extend for a separate desktop. The exact port and cable depend on the all-in-one’s model; a port’s shape alone does not prove it can send video.
Check the all-in-one’s video output and the monitor’s input
Look up the exact all-in-one model in its manufacturer’s specifications or manual and check which ports are supported as video outputs. Then check which video inputs the monitor accepts. Match an output on the PC to an input on the monitor; do not assume that a port is an output just because it is HDMI or is positioned near other connectors.
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ASUS’s external-monitor instructions cover all-in-one PCs as well as other PC types and describe connection options including HDMI, USB-C and DisplayPort. The right connection still depends on what your particular PC model supports. See ASUS: How to Connect One or More External Monitors.
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When USB-C can carry video
A USB-C connector supports video only if the PC’s particular port implements a compatible video mode, such as DisplayPort Alternate Mode, and the cable or adapter supports it too. Some USB-C ports carry data or power but not video. Confirm the port’s capabilities in the PC documentation before choosing a USB-C cable or adapter. Microsoft explains the requirements in its external-monitor connection guidance.
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Connect the monitor and extend your desktop
- With the PC and monitor ports confirmed, connect the video cable directly between the all-in-one’s video output and the monitor’s matching input where possible.
- Turn on the monitor. If it does not show the PC automatically, use the monitor’s input control to select the input that matches the connected cable.
- On the PC, press Windows key + P and choose Extend. This spreads the desktop across the two screens. Choose Duplicate only if you want both screens to show the same image.
- Open Settings > System > Display to identify detected displays, arrange them to match their physical positions, and adjust display settings. If the second screen is missing, select Detect.
Microsoft documents these projection and display-setting options for Windows 11 and Windows 10 in its guide to using multiple monitors. Windows 10 support ended on October 14, 2025; these setup steps remain relevant, but Microsoft no longer provides standard free security updates or technical support for that version.
Choose a connection that fits both devices
There is no universal best cable for all-in-one PCs. Choose based on the confirmed PC output, the monitor input, and—if needed—the video mode supported by both the PC port and the adapter.
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- INCREDIBLE CONTRAST: The VA panel produces brighter whites and deeper blacks. You get true-to-life images and more gradients with 16.7 million colors
- THE PERFECT VIEW: The 178/178 degree extra wide viewing angle prevents the shifting of colors when viewed from an offset angle, so you always get consistent colors
| Connection option | What to confirm |
|---|---|
| Direct HDMI or DisplayPort cable | The all-in-one has the matching video output and the monitor has the matching input. Verify the port’s function in the PC documentation. |
| USB-C cable or adapter | The specific PC port supports video Alternate Mode, such as DisplayPort, and the cable or adapter supports the required mode. USB-C connector shape by itself is not confirmation of video support. |
| Manufacturer-compatible dock or USB video adapter | The all-in-one model and graphics adapter support the device and the number of displays you want. Ask the PC maker or check its model documentation. |
| Display splitter | A splitter duplicates one signal; it does not create independent screens for an extended desktop. |
Microsoft’s troubleshooting guidance notes that splitters duplicate the signal and that additional displays depend on graphics-adapter capacity and supported outputs.
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Troubleshoot a second monitor that does not work
- No image: Make sure the monitor is powered on and set to the input used by the cable. Reseat both ends of the cable and confirm it connects a PC video output to a monitor input.
- The screen mirrors instead of extending: Press Windows key + P and select Extend.
- USB-C adapter gives no image: Check that the particular PC port supports the adapter’s video mode, that the adapter and cable support it, and that the monitor is on the matching input. Test a direct connection if possible.
- The monitor is not listed in Display settings: Open Settings > System > Display and select Detect. Temporarily disconnect docks or dongles to see whether they are causing the problem.
- You want more than one external monitor: Check the PC manufacturer’s documentation for graphics-adapter display limits and model-specific dock or adapter compatibility. A splitter will not provide separately usable screens.
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