Your laptop connects to an external monitor through a USB-C hub. The HDMI display works perfectly, but the keyboard, mouse, or USB flash drive plugged into the monitor's USB-A ports is not detected.
Why does the screen work while the monitor's USB ports do nothing?
The most common reason is a missing USB upstream connection. HDMI carries video and audio, but it does not automatically connect the monitor's built-in USB hub to your computer. You need a separate USB data connection to activate those downstream ports.
Understanding the two connection paths can help you fix the problem without replacing your monitor or USB-C hub.
1. Why HDMI Works but Your Monitor's USB Ports Don't
Many monitors include a built-in USB hub with several USB-A downstream ports. These ports can connect accessories such as:
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Keyboards and mice
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USB flash drives
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External storage devices
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Webcams and other USB peripherals
However, the monitor also needs an upstream USB connection to communicate with the computer.
Think of the monitor as having two separate functions:
| Connection | Purpose |
|---|---|
| HDMI | Sends video and audio from the laptop to the monitor |
| USB Upstream | Connects the monitor's built-in USB hub to the computer |
| USB Downstream | Connects keyboards, mice, storage, and other peripherals to the monitor |
This means a working HDMI picture does not prove that the monitor's USB hub is connected.
Dell explains this distinction in its guide to why a monitor needs a USB upstream connection. HDMI and DisplayPort provide video and audio, while a separate USB upstream cable establishes the data connection.
2. Understand Upstream and Downstream USB Ports
Before connecting more cables, identify the USB ports on your monitor.
USB Upstream: Connects the monitor to the computer.
Common upstream connections include:
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USB-B: Usually a square-shaped port used with a USB-B to USB-A cable.
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USB-C: Available on some monitors for upstream USB data, and sometimes video and power as well.
USB Downstream: Connects your accessories to the monitor.
These are usually USB-A ports located on the back or side of the monitor.
The direction matters. Connecting a keyboard to a downstream port will not work unless the upstream connection is established.
LG's official guide on how to activate a monitor's built-in USB hub also explains that the monitor must be connected to the PC with a compatible USB cable.
3. Build the Correct HDMI + USB Connection
If your monitor has an HDMI input and a USB-B upstream port, use two separate connections.
Video Connection:
Laptop → USB-C Hub → HDMI → Monitor
USB Data Connection:
Laptop → USB-C Hub → USB-A Data Port → USB-B Upstream → Monitor
Then connect your keyboard, mouse, or flash drive to the monitor's USB-A downstream ports.
The complete setup looks like this:
| Connection | Cable Required |
|---|---|
| Laptop to hub | USB-C host cable |
| Hub to monitor | HDMI cable |
| Hub to monitor upstream port | USB-A to USB-B data cable |
| Monitor to keyboard or mouse | Standard USB connection |
If your monitor has a USB-C upstream port instead, check its manual and use a compatible USB-C data connection. Not every USB-C port on a hub supports downstream data.
Important: Do not confuse a USB-C PD charging input with a USB-C data port. A charging-only port cannot replace the USB upstream connection.
4. Check Whether the Monitor's USB Hub Is Enabled
If the upstream cable is already connected but the USB ports still do not work, check the monitor's settings.
Some monitors include multiple video inputs, USB upstream connections, or built-in KVM functionality.
Look for these settings in the monitor's on-screen display (OSD):
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USB Source or USB Upstream Source
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USB Hub Enable/Disable
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KVM Input Selection
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USB-C or USB-B Upstream Selection
If your monitor supports multiple computers, make sure its USB upstream source corresponds to the laptop currently using the display.
Also check whether the monitor requires its power adapter to be connected for the USB hub to operate.
The exact menu names and available options depend on the monitor model.
5. Use These Tests to Find the Missing Connection
If the monitor's USB ports remain inactive, compare a few simple configurations.
| Test | Result | What to Check |
|---|---|---|
| USB device works directly on laptop | Device is functional | Monitor upstream connection |
| USB device works through hub but not monitor | Hub data works | Monitor upstream cable or OSD settings |
| USB device works through monitor when connected directly to laptop | Monitor USB hub works | Hub data connection |
| No USB devices work through monitor | Multiple devices affected | Upstream cable, monitor USB hub, or settings |
Start with a basic wired mouse or USB flash drive rather than connecting several devices simultaneously.
If the monitor's USB ports work when the upstream cable is connected directly to the laptop but fail when routed through the hub, investigate the hub's USB data ports and connection compatibility.
For a separate issue involving the hub's own USB ports, see our guide to USB-C hub HDMI and USB data connection issues.
6. Choosing a USB-C Hub for Monitor and USB Expansion
If you regularly connect an external monitor and multiple USB peripherals, choose a hub that provides both HDMI video output and dedicated USB data ports.
For a workstation that also needs wired networking, a USB-C hub with HDMI and three USB 3.0 data ports combines HDMI output up to 4K@30Hz, three USB 3.0 ports, and Gigabit Ethernet.
For users who need more USB connections, a USB-C hub with HDMI and four USB 3.0 ports offers HDMI output up to 4K@30Hz, four USB 3.0 data ports, and up to 60W USB-C Power Delivery pass-through. Its longer host cable also provides more flexibility when arranging a desktop workspace.
Both configurations can provide a USB-A data connection for a compatible monitor's USB-B upstream cable while HDMI handles video output.
Before choosing either option, confirm the laptop supports USB-C video output and that the monitor's upstream cable matches the available hub data port.
FAQ
Why do my monitor USB ports not work through HDMI?
HDMI carries video and audio, not the USB data connection required by the monitor's built-in USB hub. Connect a separate USB upstream cable between the monitor and computer.
Do I need both HDMI and USB cables for my monitor?
If you use HDMI for video and want to use the monitor's USB-A downstream ports, generally yes. You need a separate USB upstream connection unless another compatible connection already carries USB data.
Can I connect the monitor's USB upstream cable to a USB-C hub?
Yes, if the hub has a compatible USB data port. For a monitor with USB-B upstream, a USB-A to USB-B data cable can connect to a USB-A data port on the hub.
Why does my monitor's USB hub work with USB-C but not HDMI?
A USB-C connection may carry video, USB data, and power simultaneously when both devices support those functions. Switching to HDMI preserves the video connection but does not automatically preserve the USB data path.
Can a USB-C PD port activate my monitor's USB hub?
Usually not. A PD-only port is intended for charging input. Use a dedicated USB data port for the monitor's upstream connection.
Final Recommendation
If your monitor displays video through HDMI but its built-in USB ports do not work, check the USB upstream connection first.
HDMI handles the picture. USB Upstream handles the monitor's USB hub.
Connect both paths correctly, verify the monitor's USB source settings, and test a simple USB device before replacing any hardware.
Once both connections are established, your monitor can work as both an external display and a USB expansion point for your laptop.
