When it debuted in 1996, USB (Universal Serial Bus) promised to fix a very real issue that computer users had dealt with for far too long. By offering a truly universal cable, it was hoped that computing would be simplified at a time when the personal computer was coming into its own. And it did, to a point, but fast-forward to 2014, and it took USB-C to really make cables universal. But, as ever, there’s a catch.
While the advent of USB-C gave us a new connector that could be used in all manner of devices, the cables themselves are a different kettle of fish. Nowadays, USB-C is used to fast-charge laptops, send high-speed data to and from external storage, and carry images to monitors. And while some cables can do all of those things, many more don’t. And with the modern desk effectively running on USB-C, that’s a problem. Because USB-C is just the name for the connectors, and the cables in between them are a minefield of our own making.
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The Power Delivery and data disconnect
Fast charging doesn’t mean fast data
If you’re buying a USB-C cable, the chances are that you’ll need it to do one of two things: either charge something, or send data to it. You might even want it to do both of those things, but unfortunately, this is where USB-C cables tend to diverge.
When making USB-C cables, companies look for ways to cut costs. That’s especially the case when bundling cables in with new devices, like a smartphone or tablet. And one way to save money when manufacturing a cable is to make it a charging cable, or a data cable. In the case of that new device, charging is probably its main job, so that’s where the manufacturer spends its money.
Modern USB-C charging cables, or USB-C Power Delivery (PD) cables, can reach incredible charging speeds. USB-C cables top out at 240 watts, which is more than enough to charge a laptop — assuming it’s paired with a suitably powerful charging brick, of course.
One great example here is Apple’s 16-inch MacBook Pro, a laptop with a huge battery that requires a lot of power to charge. It comes with a USB-C charger rated for 140 watts and a USB-C to MagSafe cable rated for the same wattage. But you can also use one of its USB-C ports and a standard cable rated for 140 watts or more and charge just as quickly.
Those same USB-C ports are also rated for USB-C data transfer of up to 40Gb/s. But you’ll pay a premium to buy a cable that supports such a high data transfer speed and 140-watt charging. It’s likely cheaper to buy two cables; one to fast-charge, one for fast data transfers.
Charging Rate
100W
USB Version
USB 2.0
Materials
Braided cable, LED display
The DisplayPort Alt Mode trap
A third variable enters the building
Image taken by Yadullah Abidi | No attribution required.
Long gone are the days of choosing between HDMI and DisplayPort cable when connecting a computer to a monitor. USB-C is a viable option right now, especially if you’re a laptop user. Connecting a laptop to a monitor via USB-C has an added bonus: the monitor can send power to the laptop as well as receive video data from it. The result is a single cable handling both video and power, the Holy Grail of laptop life.
If only it were that simple. As you’ve no doubt figured out by now, the USB-C cable needs to be capable of sending enough power to the laptop to charge it. But that’s not all, because it also needs the requisite chips and pins to send an image in the opposite direction. And not all USB-C cables have those chips and pins.
The magic term here is DisplayPort Alt Mode, often simply referred to as Alt Mode. Without it, a USB-C cable can’t send a video image to a monitor. But that’s just the beginning, because even if the cable supports Alt Mode, it might not be capable of handling the resolution you want it to.
As a rough guide, the faster the cable can transfer data, the higher the resolution video it can send to a monitor. Cables rated for 10Gbps tend to handle resolutions of 5K and even 8K. The same applies to refresh rates, with higher quality, faster cables capable of higher resolutions and faster refresh rates than cheaper, flimsier ones.
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Choosing the right cable for your needs
Time to get specific about specifications
If you’re buying a new USB-C cable, it’s vital to check that it is capable of doing what you want it to do. If it’s data transfer speed that you’re looking for, there are some labels to look out for.
All USB cables should be labeled in terms of which USB “version” they are. These labels are rarely, if ever, on the cable themselves. But they should be available at the point of purchase. Cables range from USB 2.0 (the slowest) to USB4 (the fastest).
USB Version
Speed
Connector Type
USB 2.0
480Mbps
Type-A, Type-B, Type-C, Mini, Micro
USB 3.0, USB 3.1 Gen 1, USB 3.2 Gen 1
5Gbps
Type-A, Type-B, Type-C, Micro
USB 3.1 Gen 2, USB 3.2 Gen 2
10Gbps
Type-A, Type-C
USB 3.2 Gen 2×2
20Gbps
Type-C
USB4
20Gbps, 40Gbps
Type-C
USB4 Version 2.0
80Gbps, 120Gbps (asymmetric)
Type-C
When it comes to buying a cable for charging, simply look for the wattage rating and make sure it’s sufficient for your needs. The minimum USB Power Delivery USB-C cable is capable of 7.5 watts. For smartphones, you’ll usually need a cable rated for at least 30 watts. If you’re charging a laptop, check with the manufacturer to see how quickly it can charge via USB-C and then buy a cable that matches.
Connecting your new USB-C cable to a monitor? Check it supports Alt Mode, or DisplayPort Alt Mode. The faster, most power-capable cables are very likely to support Alt Mode, but it’s always worth checking.
Doesn’t matter if you’re charging a Nintendo Switch or transferring data to an external SSD — you now have the knowledge you need to make sure you buy the right cable first time, every time.
