Most of us probably have a collection of random USB-C cables that have arrived over the years with various devices and peripherals or were purchased quickly as needed. Apart from the difference between smooth and braided cables and the colors—most of mine are either white or black—they’re nearly impossible to tell apart. Someone who is more obsessive than I might have labeled them when they arrived, but I suspect most people just toss them in a drawer, box, or bag. I’ll show you mine if you show me yours (yes, I still keep some things in 3.5-inch floppy boxes).
But not all USB-C cables are created equal. Even beyond the difference between Thunderbolt and USB, USB-C cables can support a wide variety of power and bandwidth specs. For instance, Apple is notorious for shipping “charge-only” cables that support data only at slow USB 2.0 speeds of 480 Mbps. And there’s no way to know what the random cable that shipped alongside some device can do.
Hardware testers exist—some of my Apple Consultants Network friends carry this Treedix USB Cable Tester—but for most people, they’re overkill. Instead, download the WhatCable app, which gives you a vast amount of information about your cables for free. A paid WhatCable Pro tier ($13.99/£9.99) lets you name cables and shows what each port, cable, and device combination can do and has negotiated.
Using WhatCable is trivially easy—you just launch the app and scroll through its reports on each cable/device that’s attached via USB-C. It shows you the port in use, the cable type in bold (Thunderbolt / USB4 in this case), a brief description of what the cable can do, and boxed summaries of the cable’s capabilities for charging, throughput, and display quality. After that, it lists all the details it can discern about the cable and what it knows about the connected devices (an Apple Studio Display in this case). If you’re a glutton for technical punishment (“please sir, more specs!”), click the Show Technical Details switch at the bottom.
Those Apple “charge-only” cables? They look a lot different in WhatCable, as you can see from this one connecting my iPhone 17 to my Mac. You really don’t want to use one of these cables to connect an external SSD.
In this case, it doesn’t matter what cable I use because the iPhone 17 itself is limited to 480 Mbps. That became obvious when I switched to my go-to OWC Thunderbolt 4 cable. Even though WhatCable correctly identifies it as a Thunderbolt cable capable of 40 Gbps, the app notes that only USB 2.0 is active because of the iPhone 17’s limitations.
It was also illustrative to plug in an Anker USB-C hub with several USB-A ports and then attach an old OWC hard drive that turned out to be limited to USB 2.0’s 480 Mbps and a SanDisk flash drive that supported USB 3.0’s 5 Gbps. I wouldn’t have guessed the hard drive was that slow just from looking at it.
I could keep working my way through the rat’s nest of USB-C cables in that bag, but you get the idea. WhatCable also includes macOS widgets so you can see what’s connected at a glance and can trigger notifications when cables connect or disconnect. You can choose between a normal windowed app or a menu bar popover, and Terminal wonks can even run it at the command line.
As long as you’re running a Mac with Apple silicon running macOS 14 Sonoma or later (Intel-based Macs are out of luck), I encourage you to download WhatCable 1.4 today and take a spin through its documentation for more details. If you regularly work with many USB-C cables, consider WhatCable Pro for its additional identification and diagnostic capabilities.
