Are All USB-C Cables Created Equally?

The USB-C connector is increasingly appearing on more and more of our devices, and that potentially means great things for the future of device connectivity. Wouldn’t it be dandy to use the same USB-C cable to connect your phone, computer, and other peripherals?

Unfortunately, there are issues to contend with that make it difficult to achieve the dream of universal connectivity without doing a bit of research first. This post goes into just one of those factors: the features supported by the USB-C cables themselves.

Are All USB-C Cables Created Equally?

No! To most consumers, we naturally might look at a cable, observe the USB-C connector on both sides, and conclude that this is a USB-C to USB-C cable. We’d be right, but there’s a bigger, more complicated picture here. While historically users could count on a cable and device working if both ends fit (and a driver was available, when needed), unfortunately it’s no longer this simple. It’s crucial to note that USB-C only represents the shape and type of connector, and says nothing about the kind of specifications and transfer speeds a cable supports.

A USB-C cable could support the following specifications:

1) USB 2.0 (480Mbps)
2) USB 3.2 Gen 1 (5Gbps)
3) USB 3.2 Gen 2 (10Gbps)
4) Thunderbolt 3 (20Gbps)
5) Thunderbolt 3 (40Gbps)
6) USB4 Gen 2 (20Gbps)*
7) USB4 Gen 3 (40Gbps)*

*Updated as of 2021

There are additional variations as each of the USB-C cables supporting a specification above can be rated and “electronically marked” to support either 3 Amp or 5 Amp charging (using a tiny embedded “e-marker” chip that tells the attached devices what features the cable supports), and complicating things further, “Active” Thunderbolt USB-C cables have even more unique characteristics, but for the purposes of this post, we will omit these variations.

Why Do These Specifications and Transfer Speeds Matter?

These matter because there are physical differences in a USB-C cable depending on what specification it supports, and as a result, different cables that look identical can behave in very different ways.

The USB-IF (USB Implementers Forum, an official authority over USB) defines USB-C cables that support either USB 3.2 Gen 1 (5Gbps) or USB 3.2 Gen 2 (10Gbps) as “Full-Featured” USB-C cables (Page 28 of USB-C Spec).

Full-Featured USB-C cables actually have 10 more wires compared to USB-C cables supporting USB 2.0 only (Page 68, 69 of USB-C Spec).

Why do these extra wires matter? One reason is “high speed” wires support the extra bandwidth of USB 3.2 versus USB 2.0. However, you also might be familiar with the fact that compatible USB-C systems can support displays, and it’s important to understand that Full-Featured USB-C cables are required for many USB-C docking stations, because they use a standard known as VESA DisplayPort Alternate Mode (“DP Alt Mode” or “Alt Mode”). DP Alt Mode and any devices that utilize it, like most USB-C docks relies on several of the extra wires in these Full-Featured USB-C cables to function as expected (VESA).

We at Plugable offer many USB-C docks that are able to drive video over a compatible USB-C connection. This is accomplished in one of three ways:

1. Docks that use USB-C Alternate Mode (Alt Mode), where a native video stream can be sent over the USB-C cable. These require a “Full-Featured” USB-C cable, because the extra wires are needed to carry the video stream over USB-C
2. Thunderbolt 3 docks require a computer with a Thunderbolt 3 USB-C port. And because of their extremely fast connection to the host (40Gbps), these docks require Thunderbolt 3 certified USB-C cables
3. Docks that use “DisplayLink” technology compress video data and use a driver and send it over almost any USB port and cable. USB-A, USB-C, USB 2.0, USB 3.0; a Plugable dock with DisplayLink can be made to work on most systems without any special USB cable considerations

So for docks that rely on USB-C Alt Mode, what if you try to use a USB-C cable supporting only USB 2.0 (and therefore lacking those 10 physical wires) rather than a Full-Featured USB-C cable? You would be in for a bad time, as any displays through the USB-C cable (and even possibly charging) will not work.

A Common Mistake With Your Plugable USB-C Graphics Solutions
You might have one of our Plugable USB-C docking stations, such as our Plugable USB-C Mini Docking Station (UD-CAM), and are thinking “The included USB-C cable is a bit short. Why don’t I swap in my Apple 2m USB-C cable?”. This will not work, since this cable supports USB 2.0 speeds only (so no video), and therefore is not compatible with our USB-C docking stations.

Not all third-party USB-C cables support video or charging, and whether or not they do boils down to what specification the cable supports. Sellers don’t always make this clear however.

Plugable offers a USB-C cable that is USB-IF certified for those looking for a USB-C cable that supports 10Gbps transfer rate with video and charging support. If a longer cable is needed, Plugable offers a Thunderbolt 3 cable (Thunderbolt 3 Certified) at a length of 2 meters or 6.6 feet, which is compatible with all of our USB-C docks.

USB-C, although revolutionary in many aspects, can still frustrating when things don’t work. For those who may be running into issues with your Plugable USB-C device and/or its cable, please contact us directly at support@plugable.com and we’d be glad to investigate further.

What has been your experiences with USB-C cables? We’d love to hear your comments below!