You plug the cable in, the monitor says no signal, and there is nothing on screen to tell you whether the fault is the port, the cable, the monitor or Windows. So people swap cables for an hour.
There is a faster way, and it starts by getting Windows to say out loud what it can see. I ran that check here with three screens attached, and the output names the connector each one is using, which is the piece everybody is missing.
Make Windows tell you what it already knows
One command, no administrator, and it ends half of these. Run `Get-CimInstance -Namespace root\wmi -ClassName WmiMonitorConnectionParams` in PowerShell, which lists every display Windows can currently see.
The VideoOutputTechnology number is the answer.
Microsoft documents 5 for HDMI, 4 for DVI, 10 for external DisplayPort and 0x80000000 for a built-in panel, in its connector reference.
Your HDMI screen missing from that list means Windows never saw it. The fault is before Windows, which rules out most of what people try first.
Your HDMI screen present in the list means Windows sees it fine. Then it is a settings question, and the settings are not where you would look.
What this laptop reported
Ours, with three screens on at the time. Three entries came back, one internal panel and two external monitors.
One external reads 5, which is Microsoft's value for HDMI. That is a working HDMI link, proved rather than assumed. The other reads 10, external DisplayPort, and I had that monitor in a different socket entirely.
So the command distinguishes them without you looking behind the desk. That is the whole point of running it.
The two-keystroke check people skip
Before anything else physical, press Windows and P together. Microsoft states the four options as "PC screen only," "Duplicate," "Extend" and "Second screen only."
A machine stuck on PC screen only shows nothing on HDMI. The port is perfectly healthy.
If nothing appears even after choosing Extend, Microsoft's next step is Start > Settings > System > Display > Multiple displays > Detect. Detect is a button, not a scan that runs by itself, and nothing prompts you to press it.
When the port is genuinely the problem
Physical causes, in the order worth checking on your own machine. Try the other HDMI socket if the machine has two. Many laptops wire one port to one graphics chip only.
Look into your socket with a light. A bent pin or packed lint stops a connection that looks seated. A loose fit is a real fault, and HDMI plugs have no latch, so a worn socket lets the plug sag out of contact under cable weight.
Wiggle the cable. A flicker is your answer, and that is a connector problem, not a driver one.
Two graphics chips, and only one may be listening
Common on laptops, and it explains a port that works for some things. This laptop has two, an AMD Radeon and an NVIDIA RTX 3050, which is a normal gaming laptop pairing.
The physical HDMI socket is usually wired to one of them. Which one is a design decision the maker made, not a setting. That is why your external screen can work on the desktop and fail in a game. Or the other way round.
The same trap bites docks harder. Through a dock there is another layer, and it has its own order.
Rule out the far end before blaming the port
Half an hour of swapping cables usually skips this, and yours probably did too. Change the monitor's input source by hand. Most monitors do not switch to HDMI on their own and show no signal while sitting on a different input.
Try the same cable into a television. A working picture there moves the fault to the monitor or its input selection. Try a different cable into the same port. Cheap HDMI cables fail, and they fail intermittently before they fail completely.
A picture that appears then vanishes is not a dead port. Flickering has its own test that splits the driver from an app.
When nothing at all appears in the list
The narrow case, and it is worth knowing where it leads. No entry with any cable, any monitor, either port, and that pattern points at the machine.
Check the socket for damage before spending money. A laptop that has been carried with a cable in has usually taken the strain at the port.
A USB-C port can often replace it. Whether yours carries video is about the port, not the adapter.
And a second monitor that will not appear at all has its own list. The first step there takes two keystrokes.
**Status: checked on 18 September 2026 on this machine, a Home edition of Windows 11 on 25H2, with three displays attached and the connector values read live.
Microsoft's driver reference supplied the connector numbers and its multiple displays page supplied the Detect route and the four Windows key and P options. No cable was swapped, no hardware was opened and nothing was changed.**
How do I know if my HDMI port is broken?
Run the connection parameters command in PowerShell with the screen plugged in.
If Windows lists an entry with a VideoOutputTechnology of 5, the port and cable are working and your problem is elsewhere. If nothing appears with any cable or monitor, the port itself is the suspect.
Why does my monitor say no signal on HDMI?
Most often the monitor is sitting on a different input, or Windows is set to PC screen only. Change the input by hand on the monitor, then press Windows and P and choose Extend before you touch anything physical.
Why does my laptop HDMI port work sometimes?
Laptops with two graphics chips usually wire the HDMI socket to one of them, so behaviour can change between a game and the desktop.
A loose or worn socket produces the same symptom, and wiggling the cable will tell you which of the two you have.
Does Windows have a button to find a missing display?
Yes, and nothing prompts you to press it. Microsoft's route is Start, Settings, System, Display, Multiple displays, then Detect. It is a manual button rather than something that runs on its own.
The Short Version
- Get Windows to list what it can see before you swap a single cable.
- VideoOutputTechnology 5 is HDMI in Microsoft's own numbering. 10 is external DisplayPort.
- Listed means the link works and your problem is a setting.
- Not listed means Windows never saw it, which is a cable, a port or a monitor input.
- Windows and P first. A machine on PC screen only sends nothing out.
- Then the Detect button, which does not press itself.
- Laptops with two graphics chips wire the socket to one of them.
- A flicker when you wiggle the cable is a connector fault, not a driver one.
Where to Next
Run the command first, because the answer decides whether you spend the next hour on hardware or on settings.
Change the monitor's input by hand before you conclude anything, since it will not do it for you. If the port is listed and still shows nothing, press Windows and P and work through the four options.
And if two ports, two cables and two monitors all fail the same way, stop testing and look into the socket. Got a connector number that is not in the list above? Drop it in the comments. That value narrows the problem a long way.
Isaac Smith is the founder and editor of PC Glance, a website that covers computers, laptops, and technology. He is a tech enthusiast and a computer geek who loves to share his insights and help his readers make smart choices when buying tech gadgets or laptops. He is always curious and updated about the latest tech trends.