Symptoms
- External monitor stays black or says 'No Signal' when connected to a laptop
- Laptop's own screen works fine
- Pressing the external display keyboard shortcut does nothing
- Worked before but stopped after an update
Likely causes
- CommonWrong display mode selected (laptop screen only)Laptops often default to internal-screen-only until you press the display toggle shortcut.
- CommonLoose or incompatible cable/adapterAdapters (USB-C to HDMI, for example) can be a weak link in the connection.
- CommonOutdated graphics driverDriver issues frequently affect external display detection specifically.
- PossibleExternal monitor on wrong inputThe monitor itself may simply be set to a different input source.
What to do
- Press the laptop's display toggle shortcut (often Windows key + P, or an Fn + function key combo) and select 'Extend' or 'Duplicate.'
- Confirm the external monitor is on and set to the correct input source.
- Reseat the cable or adapter at both ends, and try a different cable or adapter if available.
- Update the laptop's graphics driver from the manufacturer's website.
- In Display Settings, click 'Detect' after connecting the external monitor.
- Test the external monitor with a different laptop or device to confirm the monitor itself works.
- Restart the laptop with the external monitor already connected, since some systems detect displays more reliably at boot.
Tools and parts
- None
Replacement cable or adapterSearch: “USB-C to HDMI adapter”
When to call a pro
If a known-good monitor, cable, and updated driver still fail to produce any external image, the laptop's video output port or graphics hardware may need professional diagnosis.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.