DisplayPort Alt Mode is the feature that lets a USB-C port send video to a monitor, and not every USB-C port has it. The connector shape does not decide it. Your laptop's port must support DisplayPort Alt Mode (DP Alt Mode for short), and the cable and the display device must support it too. You can check in four ways: read the symbol next to the port, look up the official spec sheet for your exact model, check for Thunderbolt or USB4, or plug in a monitor and see whether it lights up.
Quick answer: A USB-C port supports DisplayPort Alt Mode if it has a DP symbol, a Thunderbolt lightning bolt, or a USB4 logo, or if the laptop's official spec sheet says so. A battery symbol usually means charging only. If the labels do not settle it, connect a known working monitor and check your display settings. A hub that uses DP Alt Mode, like the Gitfos C1Pro, needs a port that passes this check.
What DisplayPort Alt Mode is
DP Alt Mode lets a USB-C port carry a DisplayPort video signal instead of, or alongside, USB data. USB-C has four high-speed lanes. In this mode, the port can give two or all four of them to video, as Newnex describes. With two lanes for video, USB 3 data can keep running on the other two. With four lanes for video, the connection falls back to USB 2.0 for data.
Which USB-C ports have DisplayPort Alt Mode
Thunderbolt and USB4 ports are the strongest candidates, and plain USB-C ports vary by model. Each port type tells you something different.
| Port type | How to spot it | Video output |
|---|---|---|
| USB-C with DP Alt Mode | DP symbol, or listed in the spec sheet | Yes |
| Thunderbolt | Lightning bolt symbol | A strong sign of yes, and the host, cable, and monitor must also support it |
| USB4 | USB4 logo | A strong sign of yes, and the host, cable, and monitor must also support it |
| Data or charging only | No symbol, or a battery symbol | No |
The symbols are common, but they are not universal, so the spec sheet has the final say.
How to check your laptop for DisplayPort Alt Mode
Start with the port symbols, then confirm in writing, then test with a monitor.
- Look at the symbol beside each USB-C port. A DP symbol, a lightning bolt, or a USB4 logo is a good sign. A battery symbol suggests charging only.
- Open the laptop maker's spec sheet for your exact model. Search for "DisplayPort Alt Mode", "DisplayPort 1.4", "Thunderbolt", or "USB4". A listing that says only "USB-C" does not settle it.
- Connect a known working monitor with a cable that lists video support. On Windows, open Settings, then System, then Display, and select Detect. On a Mac, open System Settings and look under Displays.
- If nothing appears, change one thing at a time: the cable, the USB-C port, or the monitor. If the same cable and monitor work on another computer, the first laptop's port likely has no video output.
Why the cable and monitor matter too
A port with DP Alt Mode still needs a cable and a display device that support it. Some USB-C cables carry only charging or USB 2.0 data and send no video. A high power rating on a cable does not prove it carries video. Look for "video", "DisplayPort Alt Mode", "USB4", or "Thunderbolt" in the cable's listing, as KTC's guide advises.
DisplayPort Alt Mode and the Gitfos C1Pro
The Gitfos C1Pro sends video through DP Alt Mode, not DisplayLink, so your laptop's USB-C port must be a full-function port that supports it. The hub's single HDMI port outputs 4K @ 60Hz. Connect it to your laptop with the included full-function USB-C cable.
What this check does not tell you
Passing the check proves your port can send video, not what resolution or refresh rate you will get.
- A port with DP Alt Mode may be limited to a lower resolution or refresh rate than 4K @ 60Hz.
- The USB-A and USB-C data ports on the C1Pro do not output video. Only the HDMI port does.
- On the C1Pro, a laptop USB-C port without DP Alt Mode will not send video, even if it transfers data.
- The C1Pro needs its 65W DC adapter connected. It has no bus-powered mode.
- Gitfos has not published video test results for individual laptop models, so use your laptop's spec sheet and a direct monitor test.
Frequently asked questions
Most questions come down to one fact: the USB-C plug shape does not guarantee video.
Does my laptop support DisplayPort Alt Mode?
Check three places: the symbol beside the USB-C port, the laptop's official spec sheet, and a test with a known working monitor. A DP symbol, a Thunderbolt lightning bolt, or a USB4 logo are good signs. A port that only charges has none of them.
What is DP Alt Mode?
DP Alt Mode is short for DisplayPort Alternate Mode. It lets a USB-C port carry a DisplayPort video signal over the same cable that can also carry data and power. The laptop, the cable, and the display device must all support it.
Do all USB-C ports support video output?
No. The USB-C connector only describes the plug shape. Some USB-C ports handle data or charging only, and send no video at all. Always confirm video output in the laptop's spec sheet or manual.
Is Thunderbolt the same as DisplayPort Alt Mode?
No, but they are related. Thunderbolt ports can output DisplayPort video, so a Thunderbolt port is a strong sign that video works. Thunderbolt adds extra speed and features on top of that.
Will a USB-C hub work if my laptop has no DisplayPort Alt Mode?
A hub that relies on DisplayPort Alt Mode will not send video from that port, although its USB data and charging functions can still work. Hubs that use a different method, such as DisplayLink, work without it, but they need a driver.
Next steps
Look up your laptop's spec sheet first, then run the monitor test to confirm. For a hub that uses DP Alt Mode with an HDMI port rated for 4K @ 60Hz, see the Gitfos C1Pro, browse more hubs and charging options, or reach the team through the support center. More buying advice lives in the Guides blog.