USB-C Explained

Tom Westrick
Aug 22, 2016 · 6 min read

If you purchase a new phone or laptop in 2016, there’s a very good chance it will use a new standard for charging and data transfer. The USB standard was introduced in 1996, and replaced the previous serial ports and PS/2 connectors. Within a few years, USB flash drives started to replace floppy disk and CD drives.


There are already a number of USB connectors. The most famous is the rectangular USB-A connector, which is used on at least one end of most cables, and used for virtually all flash drives. Next is USB-B, a slightly more square version. There are also mini and micro version of both USB-A and USB-B, with the Micro-USB B used on every smartphone not made by Apple in the last four years.

Mini and Micro USB-B

The latest and greatest plug is USB-C, which fixes a lot of the problems with the A and B plugs. Like Apple’s Lightning cable, the plug is reversible, so there’s no such thing as putting it in upside down. It’s also reversible in the sense that there are USB-C to USB-C cables, and as the video below shows, data and power can be transferred both ways.

A USB-C port can be used for other protocols, such as HDMI and DisplayPort to transmit video from a laptop to a monitor. Thunderbolt 3, the latest version of Intel’s protocol for transmitting data, charge and video simultaneously, also uses a USB-C port for its latest version. Some laptops like the HP Spectre 13 only have USB-C/Thunderbolt ports, all three of which can be used for charging, data transfer and transmitting video.

A USB-C to HDMI adapter

The confusing part of having one cable to rule them all is there’s not a very easy way to tell what a particular port will do just by looking at it. For example, both my laptop and my phone have a USB-C port, though my laptop uses a different port for charging. My laptop can use the USB-C port for displaying video on an external monitor, but my phone cannot.

Moreover, there’s no easy way to tell what speed your cable is. The USB 3.0 protocol is — theoretically — ten times faster than the USB 2.0 protocol. On the USB-A and USB-B ports and plugs, there’s usually a blue insert to identify that cable/port uses the faster USB 3.0 protocol. Because the USB-C ports and plugs are so small, there’s no room for a similar identifier. The plug may have a symbol next to it to note its function, but the lightning bolt to note its a Thunderbolt port can be easily confused for a charging-only port.

When it comes to interacting between your PC and phone, USB speeds may not matter. Using a USB 3.1 cable, I tested a common task for smartphone owners: syncing music from your phone to your computer. The test devices were my Nexus 6P — with USB 2.0 speeds — and a friend’s HTC 10 — with USB 3.0 speeds. Both phones were connected to my laptop’s USB-C 3.1 port, and I used the same USB-C 3.1 cable to sync the same 4 gigabyte music library. Both phones use the same speed of internal storage, so the only real difference is the speed of their USB ports. However, the Nexus 6P was finished syncing in 16 minutes 11 seconds, while the HTC 10 wasn’t finished until 19 minutes 10 seconds. So even if your phone uses the slower port, it may not be a big deal.

One great thing about all the functions of a USB-C port is that it allows laptop makers to make thinner devices, or used internal room for other components. It can also give consumers more flexibility: if a laptop (such as the 2015 Chromebook Pixel)has a USB-C port on both the left and right sides, consumers can choose which side to use for charging or video transmission depending on their current setup.

One bad aspect related to USB-C is the quick charging standard: out of the box, a USB-C device connected to the proper USB-C charger can utilize a quick charging method using the USB Power Delivery protocol. Like other quick charging methods, the target device can draw extra power when the battery is lower, and the charging speed will gradually taper off as the battery fills up. Out of the box, this is already a pretty good solution. The trouble is, some phone and cable manufacturers have implemented their own quick charging standard which is incompatible with the already established USB Power Delivery standard, and it could cause harm to devices in the long run. Buying USB-C cables is already a bit difficult since they’re not available at many brick and mortar stores, and the incompatibility adds additional difficulty to it.

A Google engineer named Benson Leung has taken to review USB-C cables and accessories, and provides an easy to use list on Amazon on which cables and accessories to purchase. Amazon has said they will delist any cables and accessories that are found to not follow the standard, though some cables the Leung has found to not follow the standard are still listed.

Another interesting aspect of USB-C is that because it can carry both audio and power, headphones can be manufactured to use a USB-C connector to both transmit audio and power to noise cancelling headphones. Traditionally, noise cancelling headphones have had to contain batteries that would need occasional recharging. JBL recently announced a pair of USB-C noise cancelling earbuds, but they haven’t been released yet.

On the flip side of the audio spectrum, some manufacturers have released phones that only have a USB-C port, and not the traditional 3.5 millimeter headphone jack that has been in use in headphones since the 1950’s. This allows them to slim down the design, but it hugely inconveniences consumers who want to use their old headphones without worrying about carrying around an adapter. It also makes it impossible to use wired headphones while you are charging the phone, since the USB-C port is occupied by your headphones. So far, Motorola and Le Eco have announced phones with only a USB-C port, though Apple is rumored to do the same thing for the next iPhones — but using their proprietary Lightning cable instead of USB-C.

At the end of the day, the current USB-A and USB-B plugs and ports will remain around for a very long time. Existing devices like flash drives, hard drive enclosures and printers will still be around with the older standards, and I highly doubt anyone is going to rush out to replace their entire set up just because of one cable. Still, there are a lot of cool things that the latest USB port can support, and I’d be curious to see a laptop with only USB-C ports (plus a headphone port) for everything.

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