I have a habit I should probably kick, but I refuse. I don’t do cable management. Instead, I twist my cords into pretzels until they snap, then buy replacements off Amazon because, frankly, who wants to pay extra for certified gear when a dollar listing does the job?
Most of the time, that gamble fails.
You order a cable boasting 70 watts. You plug it in. It charges. Great, right? Not really. Often, that new cable throttles the output, leaving your high-end wall brick working at half capacity. It’s frustrating. It’s slow. And for a long time, there was no way to prove the cable was the bottleneck unless you already knew what to look for.
Then comes the Mac.
Specifically, a Mac with Apple silicon. If you’re rocking an M1, M2, M3, or M4 chip, you have access to a hidden goldmine of diagnostic data. There is a free tool called WhatCable that grabs that backend telemetry and spits out the truth about what is plugged into your Thunderbolt and USB-C ports.
WhatCable Explains Your Connection Bottlenecks
Here is how the trick works. Every legitimate, higher-quality USB-C cable has a tiny chip inside it called an e-marker. This little brain tells the host device (your computer) how fast the cable can go. Can it push 100 watts of power? Can it handle 40Gbps of data? Does it support DisplayPort Alt Mode?
Macs collect this handshake data automatically. The WhatCable application just digs it out, visualizes it in a clean, real-time chart, and translates the jargon into human language. It highlights where your setup is getting throttled. Is it the brick? Is it the cable? Or are you just stuck on USB 2.0 speeds while trying to move massive files?
The app also features a community database. If you own an obscure, generic brand cable that doesn’t register correctly on its own, you can cross-reference its characteristics against WhatCable’s user-submitted catalog to get an ID. It saves you from throwing perfectly good hardware in the trash based on a faulty gut feeling.
The Limits of Electronic Marker Reliability
But here is the rub: WhatCable isn’t magic. It is only as smart as the information it receives from that e-marker chip.
If you buy a super cheap, no-name USB-A to USB-C cord, it likely doesn’t have an e-marker. In that case, WhatCable won’t know its capabilities because it never asked. Apple’s macOS is also conservative. It generally only requests this identification handshake when it’s actively establishing a connection that needs verification, not just by looking at a plug sitting on the desk.
Furthermore, bad actors exist. Some cables advertise specs they don’t physically possess by spoofing their e-marker data. The Verge’s Sean Hollister, who has a nose for this sort of thing, found that several of his cables lied to his Mac. WhatCable reported one capability; reality, measured differently, told a different story.
That said, if you are experiencing slow charging or dropped video connections, WhatCable still gives you concrete evidence. You stop guessing if your $80 wall charger is broken and realize you’ve been feeding it through a 60-watt pipe for months.
Availability and Cost
Right now, you can’t use this tool if you run Windows. The reason is simple architecture. Microsoft’s Windows API doesn’t expose that low-level USB power negotiation data to third-party apps. So, unless the creators port the tool over—and Darryl Morley, the developer behind WhatCable, has mentioned a Linux version is in the works—you’re looking at Apple devices only for this diagnostic.
Morley declined immediate comment when asked about future platform support or the intricacies of Windows detection limitations, leaving Windows users in the dark for now.
For the rest of us, the free version does the heavy lifting. However, if you’re a power user who wants deep dives, WhatCable Pro exists. For about £10 ($13), you unlock cable history logs, real-time power monitoring graphs, and more granular diagnostic details.
Most people just want to know if their phone is charging at top speed or slowly trickling in. That part is covered in the free tier.
We’ve all got a drawer full of mystery cords. Next time one seems to fail, don’t just toss it. Plug it in and see what it actually is.
