Watch Out: How to Buy a USB Type-C Cable That Won’t Damage Your Devices

USB Type-C brings a new universal connector to laptops and smartphones, and many devices are already starting to use it. But beware: many USB-C cables aren’t designed properly and could potentially damage your hardware.

Before buying any USB Type-C cables for your new devices, you should look up whether the cable is actually compliant with the USB-C specification. More people are sure to run into this problem as more USB Type-C-enabled devices are released.

Why a Bad USB-C Cable Could Damage Your Hardware

To be clear, the problem is specifically with cables that feature a USB Type C connector on one end and an older USB connector on the other end. For example, most devices still use USB Type A–the port you think of when you think “USB”. So if you get a USB Type-C device, you may want a USB-C-to-A cable to charge it on your older laptop or older power blocks.

Here’s the problem: USB Type-C devices can support faster charging, which is great. But most USB Type-A devices were never designed to provide as much power as a USB Type-C device can take.

For example, let’s say you have a computer with an older USB (Type-A) port and a new smartphone with a USB Type-C port. You’d connect the computer to the smartphone with a USB-Type-A-to-Type-C cable. A properly designed cable is supposed to prevent the smartphone from drawing too much power from the computer’s older USB port. A bad cable that isn’t designed properly will allow the smartphone to attempt to draw a larger amount of power, though, which could damage your computer or its USB port. It could damage a charger brick or USB hub, too–this isn’t just a problem when charging from a computer.

The problem, specifically, is that many cables aren’t compliant with the USB-C specification and have a bad resistor value. Benson Leung, a Google employee who’s worked on the Chromebook Pixel and Pixel C hardware, has an FAQ on Google+ with more details. “The Type-A port and the vast majority of the devices that have Type-A ports were never designed to support 3A charging,” he writes. It’s the cable’s job to ensure a device charging from it doesn’t attempt to pull too much power. In an improperly designed cable, “the cable lies to the phone by telling the phone it’s attached to a pure 3A charging path, like the C-to-C cable to the OEM 3A charger that ships with the Nexus 6P/5X. The phone will attempt to draw 3A, but that may damage the weaker device you have the Type-A end of the cable plugged into.”

Even Smartphone Manufacturers Have Shipped Bad Cables

This isn’t just a theoretical problem. The only reason we haven’t heard much about it yet is because so few USB Type-C devices are out there in the wild, but this will change. Many cables–particularly less expensive ones–are not designed properly and will have this problem.

But it’s not just less expensive cables. Even the charging cable Oppo shipped with its OnePlus smartphone is a bad one. It doesn’t cause a problem when charging Oppo’s own OnePlus phone. However, plug that cable into another phone like Google’s Nexus 5X or 6P, and it could damage your devices. For whatever reason, manufacturers who design and manufacture these cables often don’t follow the specification properly.

How to Find a Cable That Won’t Damage Your Devices

Before purchasing a cable with a USB Type-C connector on one end and an older USB connector on the other, you should ensure it’s compliant with the USB-C specification and won’t damage your devices.

Leung has been frantically reviewing cables on Amazon, and you can find a long list of his reviews on his Amazon profile. Before buying a cable, check to see if he’s reviewed it. Skip the cable if he gave it a bad review and feel free to buy it if he gave it a good review. For now, it’s probably best to avoid buying any cables that haven’t been tested.

If you don’t want to dig through his Amazon reviews, you can visit the USB-C Compliant website, too. This website lists cables that have been reviewed and are known to be properly designed. Select a compliant cable from their list and you shouldn’t have to worry.

Hopefully, this is just a teething problem, and these noncompliant cables will vanish from the market as more people get USB Type-C devices. They also won’t be a problem once all the older devices with USB Type-A ports are gone, but that will take a long time.

The problems here demonstrate why Apple’s system of only allowing certified third-party Lightning cables to function isn’t such a crazy idea. A more open hardware ecosystem is great, but manufacturers need to do a better job of designing safe cables.