Does USB Passthrough Add Latency? 

No, mechanical USB passthrough does not add significant latency for USB devices connected via a passthrough connection.

And while this might seem like a definitive answer there’s a bit more to this question than you might think.

One side believes USB passthrough can add a small amount of latency, while others argue that it has no effect on performance at all. 

But there are a number of factors that can actually cause latency in USB devices.

So let’s take a look at this topic in more detail.

What is Latency?

Latency refers to the delay between an action and the response that action receives. This is typically on an electronic circuit or within a computer system or its connected peripherals.

When we’re talking about USB passthrough, latency refers to the delay between a keystroke on a device connected to the passthrough and the corresponding action on the computer.

The same principle applies to when you click a mouse button and the cursor then reacts on the screen by activating whatever function you wanted.

What is USB Passthrough?

USB Passthrough is when a USB device features an additional or spare USB port. This allows you to connect another USB device to the passthrough port.

Which is ideal if you have a limited number of USB ports on your computer.

A typical example of a USB passthrough is when a keyboard has an additional USB port where you can connect USB devices such as a mouse, headset, or USB drive directly to the keyboard, which then passes the USB signal through to the computer.

So that’s where it gets its name.

Some monitors also feature USB ports but these are often in a “hub” configuration.

This means you’ll need to connect your monitor’s USB port to a spare USB port on your computer and then your other USB devices to the “passthrough” port on the monitor.

Once connected it the additional USB ports on your monitor will act like any other USB passthrough port.

How Does USB Passthrough Work?

USB Passthrough can be done in two distinct ways: hardware passthrough and software passthrough. 

Hardware passthrough involves a physical connection between the keyboard and the computer. 

Software passthrough involves a virtual connection between the keyboard and the computer, where the keyboard’s USB signal is passed through to the computer’s software.

How Does USB Passthrough Affect Latency?

The impact of USB passthrough on latency can vary depending on the specific device and how it’s set up.

Mechanical passthroughs (physical ports), which act as an extension cord of sorts, have very little impact on latency. 

Emulation-based passthroughs, on the other hand, can add some lag to the system, particularly if the USB controller is busy with multiple connections.

The main thing to remember here is that the impact of USB passthrough on latency is pretty much zero, particularly for everyday use. 

You’d have to actually measure it to even notice it.

And as USB technology improves, latency will stop being something we talk about in relation to USB connections.

Factors That Can Cause USB Passthrough Latency

Hardware Factors

USB passthrough latency can be influenced by several hardware factors such as:

USB Hub Type: The type of USB hub used can affect the latency introduced by the passthrough. Slow hubs can introduce a latency of tens of microseconds.

USB Cable Quality: Poor-quality cables can introduce additional latency, while high-quality cables can minimize latency.
Device Power: USB devices that require more power can introduce additional latency.

Software Factors

Software factors can also impact USB passthrough latency like the following:

Operating System: Some operating systems may introduce additional latency due to their drivers or other software.
Device Drivers: Poorly optimized or outdated drivers can introduce additional latency.

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