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Upstream vs. Downstream USB Ports: What’s the Real Difference?

upstream vs. downstream usb ports

Upstream vs. Downstream USB Ports: What’s the Real Difference?

Key Points

  • Upstream USB ports can transmit power to a device, but it never will receive it, while downstream USB ports only receive power from a device.
  • Both upstream and downstream USB ports are capable of data transmission, but the method of transit is different.
  • You’ll usually find only one upstream USB port on a device, while there can be multiple downstream ports on the same device.
  • There isn’t an inherently better or worse choice between upstream and downstream USB ports, as you need both to make a connection from an accessory to your computer.

Upstream vs. downstream USB ports: which should you use? The Universal Serial Bus standard has seen a slew of changes since its initial introduction. While USB Type-C largely eliminates the need for both upstream and downstream ports, there are still several peripherals using the older standard. As such, it can be a bit daunting to determine what separates these ports.

Today’s guide will take a closer look at both ports. We’ll also discuss how they are best employed, and common places where you might see them. Honestly, it isn’t too difficult to determine which to use given a little insight into the technology. I will go ahead and say that USB Type-C integrates both functions of downstream and upstream into a single cable.

Upstream vs. Downstream USB Ports: Side-by-Side Comparison

Upstream USB PortsDownstream USB Ports
Intended PurposeIt provides power and transmits data to a destination.The purpose is receiving power and the transmission of data.
Data TransmissionYes, upstream can send data.Yes, downstream can receive data.
Power DeliveryUpstream can provide power to a device.Downstream can only receive power from a device.
Typical Number of Ports on a DeviceYou’ll typically only find a single port for use.There can be multiple downstream ports on a device.
Symbol UsedUSB port pointing up.USB port pointing down.

As you can likely see, there is a very clear and distinct difference between both of these ports. However, that isn’t doing the topic full justice. We’ll explore further the capabilities of these ports, and where you’ll see them commonly used.

Upstream vs. Downstream USB Ports: What’s the Difference?

Upstream and downstream USB ports are two sides of the same coin, as you can likely imagine. You’re more likely to find downstream USB ports for the vast majority of peripherals like keyboards, mice, and more. Upstream USB ports are rarer, as a whole, but they’re still out in the wild. They have a more specialized utility, and as such, they aren’t needed for everything.

Power Delivery

upstream vs. downstream usb ports
You can find upstream ports on devices that actively deliver power elsewhere.

The first real distinction to make when looking at both of these ports is power delivery. Upstream USB ports can transmit power to a device, but it never will receive it. This is contrasted by the downstream USB port, which only ever will receive power from a device.

This leads to some interesting use cases when looking at things strictly from a power perspective. You wouldn’t use a downstream USB device to provide a powered connection to something, instead, it will derive current from the likes of a downstream USB port on a PC.

Upstream ports are always going to be one way to provide current. Think of it as something like a printer or USB monitor. Further, an upstream port can be used to deliver power to downstream ports, and this is by design.

Data Transmission

Both upstream and downstream ports are capable of data transmission. However, the method of transit is a bit different as a whole. Transmission of data is typically a one-way process when looking at both of these ports. If you’ve got an external hard drive enclosure, this is quite easy to understand.

The downstream port will connect directly to your PC or laptop. The upstream port connects to the back of the enclosure. This starts a two-way handshake between the downstream and upstream USB ports and allows the continued transmission of data. Upstream will allow for the external hard drive to send data to the host computer.

Downstream will appropriately receive said data. When the process is reversed, like dragging a file from your computer to the hard drive, the process begins anew.

Connector Difference

upstream vs. downstream usb ports
There won’t be an inherent difference between the look of an upstream or downstream port connector.

Strictly speaking, there doesn’t have to be much of a difference between the USB ports to effectively allow for functionality as an upstream or downstream. You can see this with something a USB Type-C device, where both connectors are effectively the same.

They may be marked as such, depending on the sort of cabling you are using to connect devices. However, this isn’t guaranteed. Simply put, one will connect to the peripheral and the other will connect to a host computer or other device.

Standards like USB Type-C use the same overall connector, so the lines are muddied. However, with some older peripherals, you can the likes of USB printer cables to send and receive transmissions from a host computer. These are different from the typical Type-A connector, being more squared-off.

Use Cases

You won’t use one of these ports on a cable without a corresponding match on the other end. As such, just about anything that you connect to a computer, tablet, car, and so forth is going to utilize both a downstream and upstream port as a whole.

It is a bit like a network connection. There are open ports on either side of a network tunnel. One port is going to send a packet, and the open packet on the other side receives it. Just about anything using the Universal Serial Bus standard is going to use downstream and upstream ports.

You’ll find upstream and downstream ports on devices like external hard drives, printers, monitors, and USB hubs among others. Downstream ports you’ll typically find intended for the likes of keyboards, mice, external audio interfaces, and anything else receiving its power and data from a computer.

Is There Any Overlap?

There isn’t necessarily any overlap when looking at upstream or downstream ports. A cable has to have both to effectively function. Something needs to transmit power and data, and something needs to receive it.

One cannot work without the other alongside it, so you’ll need to keep this in mind when considering any sort of overlap. You’ll see similarities across the board with similar cabling standards, like HDMI. HDMI has a downstream and an upstream, but the connectors and ports are visually identical.

It can seem a bit confusing as a whole, but it always is a two-way handshake when looking at the upstream and downstream standards. The core functionality of both ports will never overlap, however.

Upstream vs. Downstream USB Ports: 5 Must-Know Facts

  • You’ll usually only find one upstream USB port on a device.
  • The connector of an upstream port can look visually identical to a downstream port.
  • How the device communicates determines whether a port is upstream or downstream.
  • Downstream ports receive data and power from an upstream port.
  • You’ll have only one upstream USB port, but you can have multiple downstream USB ports on the same device.

Upstream vs. Downstream USB Ports: Which One Is Better? Which One Should You Choose?

There isn’t an inherently better or worse choice when it comes to upstream vs. downstream USB ports. Instead, you’ve got to have one to use the other essentially. The USB standard is a fascinating revolution to computing and has allowed for operating one to be more openly accessible. Anyone using a computer is going to make use of both upstream and downstream ports.

That said, there is one core function assigned to both upstream and downstream ports, so there isn’t a choice in which one you use. You’ll inevitably end up having to employ both just to make a connection from an accessory to your computer. This further extends to things like a power adapter for your MacBook, which utilizes the power delivery function of the USB 3 standard and an upstream port.

Frequently Asked Questions

Can you have an upstream USB port without a downstream port?

Sure, but the upstream port is going to provide power and data to a downstream port somewhere else.

Do the ports have to be on the same device?

Not at all, they can be on two different devices at the same time.

Do you need both ports for everything to function?

Yes, you need both ports for transmission to occur.

How old is the USB standard?

The USB standard debuted in 1996.

Can USB provide power?

Yes, the USB 3 and 4 standards allow for up to 240 watts of power to be delivered to a device.

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