USB-C DisplayPort alt mode


If you want to send a display signal from your computer to a pen display via a USB-C cable, then the ports and cables need to support DP alt mode (DisplayPort Alternative Mode).


Support for DP alt mode is something you must verify for your ports and yoour cables. Sometimes this is not straightforward to do. You will find multiple techniques described below.

Verifying if your USB-C port or cable supports DP alt mode

Option 1: DisplayPort alt mode symbol

The DisplayPort symbol indicates the cable or port supports DP alt mode. Unfortunately many cables that DO support DP alt mode, do not have this logo.

Option 2: Thunderbolt symbol

The Thunderbolt symbol indicates a cable or port supports DP-alt mode.

Here is an example of two USB-C ports with the Thnderbolt symbol

Here is an example of a cable with a Thunderbolt symbol.

Unfortunately, many USB-C thunderbolt ports and cables simply do not have the thunderbolt logo on them.

Option 3: Unlabeled ports and cables

If your cable or port, does not support DP alt mode, you have several remaining strategies:

  • Read the documentation. Look for for the words "Thunderbolt" of "DP alt mode". Sometimes the documentation will say something more ambiguous like "supports display".

  • Contact product support from your manufacturer. Just ask them!

  • Reach out to an online community and ask if anyone has been able to use that port in their tablet to receive a display signal.

Things go keep in mind

  • You have to verify DP support for the USB-C port AND the USB-C cable. Just having one support DP alt mode is not enough.

  • DP alt mode has nothing to do with whether the port or cable can carry power or carry enough power. That is a separate issue.

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