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Why do USB connections take three tries?



USB meme
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It happened to everyone: you try to plug in a USB connector and it doesn̵

7;t work. So you flip it and it still doesn’t work. Frustrated, you flip it a third time – and it fits! Why is this experience so common with USB?

Decades of flipping USB cables

We’re talking classic USB hardware here – specifically the “type-A” connector that dates back to the initial release of USB in 1996.

Modern USB-C connectors don’t have this problem. You can connect them in both ways. The design of USB has definitely improved and the problem disappears.

But we’ve been turning those USB sticks back and forth for decades. So let’s see why that is.

RELATED: 25 years of connecting to USB (after three tries)

The Joke Explanation: USB superposition

Many nerds have speculated that USB connections have some sort of ‘superposition’. You have to spin a USB device three times because it has three states: up, down, and a third position that we don’t fully understand. Only in this position is the connection in a correct, pluggable condition.

That’s all pretty funny, but of course it’s just a joke. It’s funny, though, because there seems to be something unusual about USB compared to the other common connectors we use every day.

These USB connection problems are a meme right now. This problem is also referred to as the “USB paradox”: if there are only two ways a USB connector fits, why does it take three tries to connect it?

A design that appears symmetrical, but is not

The inside of a USB port and connector.
maxuser / Shutterstock.com

Physically, a USB type-A connector appears to be symmetrical. It is rectangular in shape. For example, unlike HDMI, there is nothing about the physical shape of the connector that makes it look like one side is up and the other side is down.

But it is! Just look into the connector and you will see that it is not symmetrical. One side should be up and the other should be down.

But unlike something like HDMI, there’s nothing about the shape that makes it easy to see which side is up and which side is down. USB is just asking for trouble.

It is unclear which side is the top

Without a clear indication of which side is actually the top of the USB cable, you don’t have much choice. Either you take a good look at the inside of the connector, or you turn it around and experiment, right?

Actually, the USB standard is trying to help.

Did you know there is something that should tell you which side the top of the USB connector is on? There is often a USB logo on top of the connector and you can see – and possibly feel it with your fingers. If you see the logo while looking at the USB connector, you know the USB connector is facing the right way and you should just be able to plug it in.

If you have a vertical USB connection, such as on the back of your monitor, the USB cable should be connected with the logo on the connector facing you.

The USB logo on top of a USB connector.
Jin Odin / Shutterstock.com.

This logo position is required by the official USB specification, but not every company follows it. Since not every USB connector has a logo, you can’t take this for granted. On some devices, the USB ports themselves are also located upside down in the device – this may be necessary to fit some components into a laptop, for example.

So not only do most people don’t know about this logo trick, but it doesn’t always work.

Even if you know the trick, you may find yourself flipping the connector three times by trial and error trying to figure out which orientation is correct.

Trial and error – but why three times?

So what do you do with a connector with an unclear design and unreliable marking of which side belongs at the top?

Of course, you can look at the inside of the USB connector and the inside of the USB port you connect it to and determine the correct orientation with your eyes. But why bother? It can be difficult to see the inside of the USB port, such as when it is on the back of a computer. It can also be dark in your room. You just have to try two orientations and see which one works – in theory.

To save time, people just try to plug in a USB device and see if it works. Didn’t it connect? Flip it over, now it will work – well, not always. Sometimes you have to turn it over again.

Again, it all comes down to USB Type-A design. When trying to connect a USB device, it is very easy to bump the edge of the connector against the edge of the USB port or the metal or plastic next to it. This feels much the same as if you had the USB connector upside down.

You probably don’t want to apply extra force or move back and forth with it – because why force it? The device may be upside down. Just turn it around and try the other way. But when even that doesn’t work, you can be sure you’re doing something wrong. You have to apply some extra force and push harder, or you have to shake the connection to align it correctly, or you have to feel the port with your finger to make sure it is properly aligned.

In other words, even if you’re a little close, a USB Type-A port doesn’t necessarily lead your connector in. There is no clear, tactile feedback that you are just missing the connection in the right direction. It feels the same as if you have the connector on the wrong way.

Considering how often people start inserting a USB device, the first try is some sort of “test” – does it get in easily? If not, it is possible that the device has been placed upside down. Turn it over and try again. If even that doesn’t work, you have to roll it back to the first position and try a little harder.

It’s not you, it’s USB

Ultimately, the problem is not with you, but with the USB Type-A connector. It’s just designed in an unclear way that leads to this problem. Why it was designed that way is a question only the designers can answer.

The good news is we’ve learned from the history of flipping USB sticks and other devices three times. USB Type-C is reversible, so you’ll never have to flip it – just plug it in either way. The USB4 standard requires USB Type-C, so USB Type-A is being phased out slowly and gradually.

One day, future generations won’t even understand the USB flipping meme.

A USB4 cable with a Type-C connector.
Alexander_Evgenyevich / Shutterstock.com

RELATED: USB Type-C Explained: What Is USB-C And Why You Want It




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