WhatCable, a free Mac app, diagnoses your USB-C cable mess (and catches counterfeits)

We live in the USB era. Almost everything that connects to our computer these days goes through an interface so ubiquitous that the word “universal” appears in its name – the Universal Serial Bus. USB has been a godsend in many ways, replacing all manner of connectors encountered in earlier technologies.

Simple, right? Well, not so much.

The problem with USB-C

Standards are great. Except when they’re not. USB-C, introduced in 2014, is the closest thing we have to “one plug to rule them all.” The problem is that despite supporting a wide range of standards, all USB-C cables look pretty much the same. A cable that supports the latest and greatest technology can look identical to a dumb charging cable. 

And, as if things weren’t complicated enough, ThunderBolt has used the same-shaped connector since ThunderBolt 3, despite being vastly more capable than standard USB.

Which is why I recently found myself staring into the abyss – in this case, a drawer in my office – trying to figure out which of the dozen or so USB-C cables in front of me was the right one to use with an SSD. I doubt I’m alone in this, and I suspect most photographers or content creators have a similar drawer or box full of cables. That’s the exact problem a Mac app called WhatCable is built to solve.

Most USB-C cables don’t include any visible information about what specs they support, so it’s worth giving credit where it’s due: This Sandisk SSD arrived in our office with a cable that clearly labels its specs (40Gpbs, 240W).Mitchell Clark

Hoping for the best, I grabbed a cable that looked new, plugged it in, and got on with finding the photos I needed. It seemed to work, so I didn’t stop to check whether I was actually getting the fastest speed the SSD could support. 

Sound familiar?

WhatCable to the rescue

I tried WhatCable on my MacBook Pro and was immediately hooked. While it’s not specifically designed for photographers or content creators, it solves a very real problem for anyone who manages lots of SSDs and card readers: ensuring the cables you use deliver maximum performance. Because if they don’t, you’re going to spend a lot more time waiting around while files transfer.

When you plug a USB device into your Mac, WhatCable will tell you everything you need to know about the cable: the generation of USB the cable supports, the speed the connected device is running at, its power delivery capabilities, and, if available, details like the manufacturer and whether it has an e-marker chip (more on that in a bit).

To my surprise, the cable I’d grabbed for my SSD not only supported its native USB 3.2 Gen 2 (10 Gbps) speed, but was actually a USB4 cable capable of up to 40 Gbps. I’d ordered some of these faster cables, thinking they’d be future-proof for a while, but since there’s no visual way to tell them apart from my older ones, I’d had no idea which was which.

WhatCable reports a cable’s USB generation, connection speed, power delivery capability and manufacturer details when you plug it in.

Analyzing the cable connecting my MacBook Pro to my Dell display is even more revealing, and gives a sense of how much detail WhatCable can report, including specifics about the built-in USB hub. You can see the details in the screenshot below.

The report for the cable that connects my MacBook Pro to my monitor is particularly detailed, including info about its built-in USB hub.

Elsewhere, the results ran the other way. When I plugged in a Samsung T7 SSD with yet another USB-C cable – short, and similar to the ones that ship in the box with many portable drives – WhatCable informed me that it could only manage USB 2.0 speeds. My guess is that it’s actually a charging cable that came with some other device.

WhatCable revealed that a cable I attached to an SSD was only rated as USB 2.0, despite looking just like the short cables that ship with many SSDs. It was probably a charging cable that came with another device.

WhatCable also includes widgets for the macOS desktop, letting you see at a glance what speed all your connected devices are running at; clicking one takes you straight to that device’s report in the app. You can also park WhatCable in the menu bar for one-click access to all your USB info.

The app includes a variety of MacOS desktop widgets that allow you to monitor USB info in real-time.

Suspicious cables

USB cables include an e-marker, a microchip embedded in the connector that acts as a kind of ID card and safety controller. It reports information such as how much power the cable can deliver, its data transfer rates, and its video capabilities, which helps your computer negotiate speed and power at levels that are safe for the connected device.

WhatCable checks whether a cable’s e-marker claims are consistent with USB-IF certification data and flags cables whose reported specs look implausible. The company’s product page describes this trust-checking feature in detail, noting that it can help surface mislabeled or counterfeit cables – a real concern when buying inexpensive cables online.

Has one of your cables gone rogue? WhatCable flags cables whose reported specs look implausible, which can help surface mislabeled or counterfeit cables.

System requirements and download

WhatCable requires a Mac with Apple Silicon (M1 or later) and running MacOS Sonoma or later. The free version is open source under the MIT license, promises no ads or tracking, and doesn’t report any analytics or telemetry back to the developer. It’s also available in 19 languages, making it broadly accessible. It can be downloaded directly from the developer.

For real nerds, there’s WhatCable Pro, which adds features like the ability to name individual cables and track their performance history, live power metering, display diagnostics, Thunderbolt link analysis, and more. It’s a one-time purchase of £9.99 (about $14) and covers up to two Macs.

So next time you find yourself staring into that abyss, not knowing which cable to grab, you know what to do. One warning: WhatCable is addictive. I found myself testing every USB-C cable in the house, and most of the DPReview staff succumbed to the same temptation after I shared it in our Slack channel. You’ve been warned.

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