ASUS's external display article applies to notebooks, desktops, all-in-ones, gaming handhelds and mini PCs. It asks you first to make sure the external monitors are set up properly and the display option you want (extend, duplicate, second screen only) is selected in Windows, then to update the BIOS, Windows packages and drivers through MyASUS, and then to check the hardware: the monitor, its cable and connectors, and a different cable or port to isolate the fault. The thin ASUS laptops offer video over USB-C or Thunderbolt, and the discrete-GPU models (ProArt P16, Zephyrus G14) also have HDMI driven by the NVIDIA GPU, so the port you use decides which graphics processor drives the screen. The ROG Ally X outputs over its USB-C port.
Differential
Likely causes of “ASUS laptops external monitor is not detected or uses the wrong resolution”, and how to tell them apart
- 1
The wrong display option
What separates it The monitor is connected but shows nothing or duplicates
How to confirm ASUS says to check the option you want is selected in Windows display settings
- 2
A bad cable or connector
What separates it The display flickers, is dark or is not detected
How to confirm ASUS says to check the monitor, its cable and connectors, and to try another cable or port
- 3
An old BIOS or driver
What separates it The monitor was detected before an update and is not now
How to confirm Update the BIOS, Windows and drivers through MyASUS System Update
- 4
A USB-C port without video
What separates it A monitor on a USB-C port shows nothing although the same monitor works on the HDMI port
How to confirm ASUS says a Type-C port must support the function you use; check the manual for DisplayPort support
- 5
A dock or hub
What separates it The monitor works direct and not through the dock
How to confirm Connect direct to test and update the dock's firmware
Before you touch a setting
Record this first — changing settings destroys the evidence
- The monitor, cable, adapter and dock, and which port on the machine it uses
- What Windows display settings list and the display mode chosen
- Whether the display works direct and not through a dock
Try in this order
0 of 7 completedSet up the monitor properly
ReversibleConnect power and video, choose the right input and pick the display mode in Windows.
Update BIOS, Windows and drivers
ReversibleUpdate BIOS, Windows and drivers, in MyASUS, System Update, which ASUS lists first, and then test again to see whether it helped.
Check cable and connectors
ReversibleCheck cable and connectors, by inspecting the monitor, the cable and both connectors, and trying another cable.
Try another port
ReversibleTry another port, by using HDMI on the discrete GPU models or a USB-C port that supports video.
Go direct
ReversibleGo direct, by removing the dock or hub, and connecting the monitor straight to the laptop.
Detect displays
ReversibleDetect displays, in Settings, System, Display, Detect, and choose Extend or Duplicate, and then test again to see whether it helped.
Restart
ReversibleRestart the laptop with the monitor attached, and then test the display again, and then test again to see whether it helped.
Model-specific
What is true of this model and not of its siblings
- Video output by model
- Zenbook S14 UX5406: USB-C and Thunderbolt plus usually HDMI and USB-A. Vivobook S15 S5507: Snapdragon X Arm laptop with USB-C. ProArt P16 and Zephyrus G14: discrete NVIDIA GPUs with HDMI. ROG Ally X: USB-C.
- GPU modes
- Armoury Crate on ROG models lists Standard, Eco, Ultimate and Optimized GPU modes; Ultimate locks to the discrete GPU for maximum gaming.
- Repair cost
- An external display fault is usually the cable, adapter or a setting and costs nothing. A port repair at an independent shop is about $129 to $179, per BadgerLayer's 2026 laptop repair guide.
- Other models this page answers
- These steps also fit the ProArt P16 H7606, ROG Zephyrus G14 GA403, Vivobook S 15 S5507, ROG Ally X handheld.
Stop boundary
When this stops being a self-service repair
- !If a certified cable on a supported port does not work after driver and BIOS updates, contact an ASUS service center
- !If the port itself is loose or damaged, book a repair
- !If only a dock fails, contact the dock's maker
Evidence ledger
Sources behind this answer
Setup, display options, BIOS and driver updates, and monitor, cable and connector checks.
USB Type-C port function and video output.
The Zenbook premium ultrabook line.
The Vivobook mainstream laptop line.
The ROG Ally handheld gaming PC line.
Exact questions
Common questions
How do I find out which USB-C port carries video?+
Look for a small display or Thunderbolt symbol beside the port, or read the specification sheet for the model code. A port with only a lightning or USB symbol may charge and move data but not send a picture.
Why does the picture flicker when I change resolution?+
A cable that cannot carry the chosen resolution or refresh rate drops the signal. Choose a lower refresh rate in Display settings, Advanced display, and if the flicker stops, the cable or adapter is the limit.
Should I update the graphics driver from ASUS or from the chip maker?+
Start with the ASUS support page for your exact model code, since ASUS packages the driver version tested on that machine. Use the chip maker's newer driver only if ASUS's version does not fix the fault.
Which ports do the ASUS laptops use for video?+
The Zenbook S14 has USB-C and Thunderbolt plus usually HDMI; the ProArt P16 and Zephyrus G14 have HDMI and USB-C; the ROG Ally X has a USB-C port for video.
Why is my second monitor dark?+
ASUS's article lists the monitor, cable, connectors and display option. Check each in turn, then try another cable.
Which graphics processor drives my monitor?+
On a discrete-GPU laptop, the HDMI port is normally driven by the NVIDIA GPU. Armoury Crate's GPU mode affects it.
Can I use an Ally X as a desktop?+
It outputs video over USB-C to a monitor or dock, as the Ally X is a full Windows PC. Use a video-capable port and charge through the dock.
Should I update the BIOS?+
ASUS lists a BIOS, Windows and driver update first for external display problems.