On many monitors, the two USB sockets are downstream ports on a built-in USB hub. They let you connect accessories such as a keyboard, mouse, webcam, or flash drive—but the hub usually needs a separate USB cable linking the monitor to your computer. HDMI and DisplayPort carry the picture, not necessarily the hub’s USB data.
What the two USB ports are for
The downstream ports are the sockets where you plug in accessories. A separate upstream port connects the monitor’s hub to the computer, or “host.” The upstream connector may be USB-B, USB-C, or another type specified for that monitor. The two downstream sockets are therefore usually two accessory connections, not two independent connections to computers.
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LG says its monitor and PC must be connected by USB to use the hub, and notes that port and cable types vary by model. LG’s monitor USB connection guide describes the setup. ViewSonic’s VG3456C guide likewise instructs users to connect the computer to an upstream port and a peripheral to a downstream port. With HDMI or DisplayPort as the video input, that monitor also needs the USB upstream connection for data transfer. ViewSonic VG3456C connection guide.
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How to connect monitor USB ports to a computer
- Identify the upstream port. Check the monitor’s rear-panel labels or manual for a port marked upstream, host, USB-B, or USB-C. Do not assume that a pair of USB-A sockets includes the upstream connection.
- Use the specified cable to connect the monitor to the computer. Match the monitor’s upstream connector to a compatible computer port, and use a cable that supports data. A charge-only cable will not establish the hub’s data link, and a cable supplied with another monitor may not be suitable.
- Connect the accessory to a downstream port. Plug the keyboard, mouse, or other peripheral into one of the monitor’s downstream sockets.
- Check the connection if the accessory does not work. Verify that the upstream cable is connected and that the peripheral is in a downstream port. Test the device directly on the computer, then check the monitor’s USB and power-saving settings.
ASUS also recommends checking the upstream connection, port roles, and standby USB charging settings when troubleshooting. ASUS monitor USB troubleshooting FAQ.
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Practical ways to use the ports
Connect a keyboard and mouse
Use the monitor’s hub for a wired keyboard and mouse or for their wireless receiver. This can make peripherals easier to reach when the computer is farther away. LG and ASUS list keyboard and mouse connections among common uses for monitor USB hubs.
Plug in a webcam or flash drive
A monitor hub can provide a convenient port for a webcam or flash drive; Dell lists both as typical accessories, alongside keyboards and mice. For storage, check the monitor manual for the port’s data speed and compatibility rather than assuming all monitor USB ports perform alike. Dell guidance on USB ports on monitors.
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Charge a phone, if the monitor supports it
Some downstream ports provide power for charging, but the available output and whether charging continues when the monitor is in standby depend on the model and settings. Do not assume a monitor port offers fast charging. Check the manual and any USB charging options in the monitor’s on-screen display (OSD).
Share peripherals between computers with KVM
A monitor with an explicit KVM feature can switch a shared keyboard and mouse between connected computers. ASUS’s Auto KVM instructions describe assigning USB upstream connections to computer or video sources. Two downstream USB-A ports by themselves do not mean a monitor has KVM; check the model’s feature list and setup instructions. ASUS Auto KVM FAQ.
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Why the ports may not work
The upstream cable is missing or connected incorrectly
If a device connected to the monitor receives power but does not communicate with the computer—or receives neither power nor data—check the upstream link first. The peripheral must be in a downstream port, and the monitor’s upstream port must be connected to the computer. In its troubleshooting guidance, ASUS notes that an unconnected upstream port can leave downstream ports unable to function or charge in the described setup.
The picture cable is connected, but USB data is not
HDMI and DisplayPort can carry the monitor’s picture while leaving its USB hub without a data connection. If the monitor uses HDMI or DisplayPort for video, connect the separate USB upstream cable when the manual requires it.
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Standby or power-saving settings disable USB
USB signaling or charging may turn off when the monitor enters standby or a power-saving mode. ASUS documents OSD settings that can affect USB detection or charging in standby. Dell advises checking the specific monitor manual to see whether a downstream port supports standby charging. A port that charges while the display is on may behave differently after the monitor sleeps.
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USB-C describes a connector, not a guaranteed set of features. A particular USB-C port may carry data only, or it may also support video, audio, and power delivery; the cable matters too. ViewSonic documents all four functions for the VG3456C’s full-featured Type-C upstream connection, while ASUS notes that a second upstream port in its Auto KVM example is data-only. Those are model-specific details, not promises about every monitor’s USB-C port or cable.
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What to check before relying on monitor USB ports
- How many downstream ports the monitor has and where they are located.
- The upstream connector type and whether the required cable is included.
- The USB data standard or speed, especially if you plan to use storage devices.
- Whether a USB-C port supports video and power delivery, and its specified power output.
- Whether charging works in standby and which settings control it.
- Whether the monitor includes KVM and supports the number of computers you want to use.
These capabilities vary by monitor, so confirm them in its manual or manufacturer specifications before choosing a cable or planning a setup.
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