How Long Can the USB Cable Be?

If you have ever tried to run an extremely long USB cable, you might have encountered a problem. USB connections have length limits, if the connection is too long it won’t work properly. In this article, we will discuss what the limits are, why they exist, and how you can overcome them.

USB different versions

The picture above shows the generations of USB standards, their transfer speeds, and their recommended length. It is surprising, but as the standards improve, the recommended length of cable doesn’t increase. Actually, the USB4 standard has a noticeably short recommended cable at only 31 inches. So, it is easy to see why some people would like to extend the length of their USB cables.

Why Is There a Length Limit for Your USB Connection?

The USB-IF sets the specifications that companies use to make USB devices. However, the length limit is a practical limitation, not an intended feature. When transmitting data, we call the units “packets.” Modern USB cables send packets in each direction and this allows your two devices to communicate with each other simultaneously. This is called “full-duplex,” as opposed to “half-duplex,” which means that the connection can only send data in one direction at a time.

When transmitting data from your phone to your computer, the USB connection sends data in one direction and then sends a confirmation back. The faster the transmission is, the faster the confirmation messages need to be. After all, if a data packet fails to send, it needs to be resent. Data packet transmission isn’t instant, increasing the length of the cable will increase the transmission time. The increase in transmission time is tiny, and as long as the length limit isn’t exceeded you won’t notice a difference.

However, high-speed cables like the USB4 specification need to be shorter. A longer cable can result in compounding data packet delivery failures, which means that the delayed confirmation will actually cause more failures.


Why Would You Need a Long USB?

There are a number of reasons you might want a long USB. For example, you might want to connect a computer to a music system. A long USB might be a good choice for a DJ who can’t afford the transmission lag or bandwidth limitations of Bluetooth connections. Wired connections are faster and more consistent than Bluetooth for data transmission.

Related article: What Do You Need to Know About Bluetooth 5.2

How Can You Extend Your USB Cable?

There are a number of ways to extend a USB connection. Here are some ideas about how you can extend the range of your high-speed data transfer connections. An important thing to remember is that adding another link in the connection can create a bottleneck. The connection as a whole will only transfer data as fast as the slowest part of the connection. 

1. USB Extension Cable or USB Hub

The most simple, and cheapest solution is to buy an extension cable. These are sometimes called passive cables. These can be tricky though. If the total connection exceeds the effective limit of the cable, as shown in the photo above, this will lead to weak signals and packet loss.

Another option is a USB hub. These hubs are great for providing extra ports, and some include a pretty long primary cable that provides an extra range. It isn’t what they are for exactly, but they can extend your USB cable in a pinch.

2. USB Repeater

A better option is a USB repeater. Another name for this product is an active USB cable. These cables are able to refresh the signal and make sure that all the information is transmitted efficiently. These cables can double the transmittable distance of a USB connection, and some cables can do even better than that!

However, the exact improvement that is possible will depend on the generation of the USB cable you are using. They cost a little more than a simple extension cable, but you can be confident they will get the job done.

UGREEN USB Extension cable

3. Ethernet Cable

Ethernet cables are generally associated with Internet access. However, Ethernet cables are not exclusively useful for the Internet. There is a lot to learn about Ethernet cables, for our purposes it is sufficient to say that these cables can transmit a lot of data, quickly, and without the same limited transmission range.

One major drawback of an Ethernet cable has is the limited port availability. More devices have a USB port than an Ethernet port. This means that if you want to use an Ethernet cable for long-distance data transmission, you will probably need an adapter to fit into the USB port.


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