This was one of those things I never thought I could go wrong with when purchasing. As simple as it sounds, I had a device with HDMI on one end. USB-C on the other hand. I spent about five minutes looking at reviews on the online store because it felt like an easy buy and I found one that looked just right. It had good reviews with its obvious “plug and play” statement.
It arrived a few days later. I plugged it in and the results were shocking. What do you mean by no signal? No picture? No error message? Just a blank screen, like nothing was connected. This made me question myself: Are my ports OK?
That’s what I didn’t understand at the time HDMI to USB-C not just one thing. There are several different types of cables and adapters, and they all do different things. Unfortunately, I learned the hard way after spending the money.
My first mistake was thinking that every cable is the same, nothing complicated
The cable looked correct but was designed for the wrong direction
It didn’t even occur to me that the cables go in different directions. I assumed it would work either way, but it wasn’t clear in my case. Most cables you’ll come across are designed to send a signal from a USB-C device to an HDMI display, so they work perfectly with laptops and TVs. There is also the reverse setup, sending the HDMI signal to a USB-C display, which is less common and generally requires completely different hardware.
In my case, I didn’t know any of that. I was trying to connect an HDMI device to a USB-C portable monitor. A cable that I now work with other than a USB-C laptop to the HDMI display. I tried it on my home TV from another laptop and it worked right away. Physically, the connectors fit perfectly. The results were so bad that I regretted believing the reviews. The cable only knew how to send signals in one direction.
There are different types of HDMI-USB-C cables
Not all ports are created equal
I’m still wondering why product listings rarely disclose this. Unidirectional cable works in one direction only. If it says USB-C to HDMI, it will only send video from the USB-C to the HDMI side. Try to reverse it and it just won’t work. Most of these cheap cables are available in the market.
As for bi-directional cables, it can work in both directions. For example, having a USB-C laptop with an HDMI monitor will work just as well as having an HDMI source to a USB-C monitor. These features are less common and usually more expensive because they have the advantage of additional hardware within the cable. The problem is that many listings out there will never clearly say which one you’re buying. You’re left to figure it out after you’ve already bought it.
Had I known about the directional restrictions, I wouldn’t have minded spending more to be sure, because that’s exactly what broke my build. A large number of people run into this all the time because the connector names make it sound like the cable should work both ways.
USB-C doesn’t always mean video
The port is exactly what I wanted, but it still wasn’t working
After the initial disappointment, I didn’t learn my lesson and thought I had just bought a generic product that had trouble processing video, or just the wrong brand. So I looked for another one. Then I discovered another problem. Not every USB-C port can carry video.
Modern USB-C is designed to handle almost everything, not just charging but also transferring data and video output, some ports only support charging, while others only handle basic file transfer with no video capability. A feature that is usually essential for displays is called DisplayPort Alternate Mode or DP Alt Mode. If your device supports DP Alt mode, the USB-C port can send video. If not, no cable will magically produce a video signal. The hard part is understanding it. Most devices do not detect this. You should either check the specs online, look for a small DisplayPort or Thunderbolt symbol next to the port, or just test with a known working adapter.
That’s when I realized that the USB-C port on one laptop is perfect for connecting to a monitor, while the USB-C port on another laptop does nothing but charge small devices or phones. This is where Thunderbolt makes things easy. Thunderbolt-enabled ports almost always handle video, data, and charging seamlessly, so there’s no need to second-guess compatibility. Now, what really happens with the DP Alt Mode feature is that the laptop sends a DisplayPort signal via USB-C, a cable or adapter will convert that signal to HDMI, and the monitor receives the HDMI signal. So this means that even though they don’t mention DisplayPort, they use it in the background. Most modern laptops and Thunderbolt ports support DP Alt mode, but many on the budget side still don’t.
Some cables are passive while others are active
Why did cheap cable fail completely?
The last thing I learned about these cables is that there are passive and active cables. A passive cable simply transmits the signal, assuming your devices already know how to talk to each other, while an active cable contains a chip that converts one signal into another. This is important because HDMI and USB-C are not the same thing, they are not the same signal.
If I were to connect a USB-C laptop to an HDMI monitor, a simple passive looking cable would work, since the USB-C device already sends compatible video via DP Alt Mode. But since I was trying to connect HDMI to my USB-C monitor, it basically required an active adapter with a conversion chip inside.
This was the last reason the cable failed. I needed an active HDMI-to-USB-C converter, but I bought a simple passive cable instead. Therefore, the cable was not a bad brand or broken; it’s just designed for a completely different use case.
The wrong cable taught me more
I made three assumptions and they were all wrong. I assumed that every HDMI-USB-C cable works both ways. I assume each USB-C port supports video. And I assumed that the shape of the connector was more important than the actual technology behind it.
The frustrating part is that product listings rarely explain any of this clearly. To attract buyers, they use words like “universal”, “plug and play”, “works with all devices”. All this means is that it works with very specific devices, in a specific direction.
