WhatCable: A macOS Menu Bar App That Finally Tells You What Your USB-C Cables Can Actually Do

We've all been there. You've got a drawer full of USB-C cables, and you have no idea which one supports 100W charging, which one does Thunderbolt 3 speeds, and which one is basically just for slow data transfers.

There's a new macOS menu bar app called WhatCable that solves this exact problem. It sits in your menu bar, and when you plug in a USB-C cable, it tells you in plain English exactly what that cable is capable of. No guessing, no trial and error.

What It Does

WhatCable is a lightweight macOS app that lives in your menu bar. Whenever you plug a USB-C cable into your Mac, it reads the cable's metadata—things like power delivery capabilities, supported data transfer speeds, and protocol support—and shows you a clear summary.

Instead of digging through System Information or cryptic ioreg output, you get something like:

• "This cable supports up to 100W charging"
• "USB 3.2 Gen 2 data speeds (10 Gbps)"
• "Thunderbolt 3 compatible"

It's that simple. No configuration, no setup. Just plug in your cable and the menu bar lets you know.

Why It's Cool

The clever part is how it gets this information. USB-C cables have built-in e-marker chips that store capability data. WhatCable reads that data directly from the cable itself using macOS's IOKit framework. It's not guessing based on brand or model—it's reading the actual certified capabilities.

Some standout features:

• Instant feedback – You don't have to click anything. The app detects when a cable is plugged in and updates the menu bar item automatically.
• Plain English output – No technical jargon like "20V/5A" or "USB 3.1 Gen 2x1". It tells you in practical terms what you can do with that cable.
• Works with any USB-C port – Thunderbolt 3, Thunderbolt 4, USB4, and standard USB-C cables are all supported.
• Privacy-friendly – It only reads cable metadata. It doesn't send anything to the network, no telemetry, no analytics.

The real-world use case is obvious: when you're about to plug in a cable for charging your laptop or transferring large files, you can instantly confirm it's the right cable. No more guessing which one from your tangle of cables actually supports 100W fast charging.

How to Try It

You can grab the source code and build it yourself from the GitHub repo:

https://github.com/darrylmorley/whatcable

The README includes instructions for building with Xcode. It's a straightforward Swift project, so if you've built a macOS app before, you'll have it running in minutes.

Alternatively, if you're just curious, the repo has some screenshots showing the app in action. The developer may also distribute a pre-built binary in future, but for now, cloning and building is the way to go.

Final Thoughts

This is one of those small, focused utility apps that makes a real difference in daily workflow. If you work with multiple USB-C devices, cables, or docks, WhatCable saves you the frustration of plugging in a "fast charger" cable that turns out to be a slow data-only cable.

It's also a nice example of using macOS IOKit to read hardware metadata—something many devs might not know is possible. If you're into low-level macOS development, the source code is worth a look.

Give it a try, and maybe finally clean out that cable drawer with confidence.

Follow us at @githubprojects for more developer tools and open source spotlights.