Everyday computer · display
External monitor shows no signal
Check the monitor input, cable, adapter and Windows display mode first. This can prevent an unnecessary hardware purchase.
Updated 14 August 2026
Quick checklist
- Make sure the monitor is on and the correct HDMI/DisplayPort/USB-C input is selected.
- Unplug and reconnect both ends; try another compatible cable.
- In Windows press Win+P and choose Extend or Duplicate.
- Try another video output or monitor, changing one thing at a time.
- With a dock or USB-C adapter, confirm that the port supports video, not only charging.
- Stop if the image flickers, a connector gets hot or the cable is damaged.
The symptom narrows the cause
A black screen can come from the wrong input, cable, adapter, display mode or a limit on how many displays the computer supports.
| Monitor says No signal | Select the correct input and change the cable. |
|---|---|
| Computer sees monitor, image is missing | Press Win+P and choose Extend/Duplicate; check resolution. |
| Works directly, not through dock | Dock, power supply or adapter may limit video. |
| Image cuts out | Cable, connector or power saving may interrupt it. |
| Image is blurry or wrong size | Check the recommended resolution and refresh rate. |
Windows
- Microsoft recommends Win+P and selecting Extend when an external monitor is not working.
- Check that the monitor is powered, the cable is secure and the correct input is selected.
- Avoid an HDMI splitter when you need two independent desktops; splitters usually duplicate one signal.
Mac
- Apple recommends checking Mac ports, the cable, adapter and the number of supported displays.
- Open System Settings > Displays, hold Option and click Detect Displays.
- Wake the Mac from sleep and check the adapter manufacturer's guidance.
What not to do
- Do not buy a new monitor before testing input, cable and display mode.
- Do not force USB-C plugs or use damaged cables.
- Do not install random drivers before basic connection checks.
- Do not change many settings at once if you want to isolate the cause.
Quick diagnosis: where does the image work?
Quick diagnosis: where does the image work?
Choose the closest situation. Your answer is neither sent nor stored.
When is help worthwhile?
If the display works directly but not through a dock, or several cables fail, JVS Tuki can separate port, adapter, settings and compatibility causes.