A free macOS app called WhatCable solves a frustrating problem: figuring out which of your identical-looking USB-C cables is which. Instead of using an external hardware tester, it reads information that your Mac already has about the cables plugged into it The Verge. The app was built by developer Darryl Morley, works on Apple Silicon Macs, and lives in your menu bar rather than taking up space as a separate window The Verge.

USB-C cables all look the same, but they are not. One cable might be rated to deliver 65 watts of power for charging, while another can handle 240 watts. Some move data at slower speeds, others at faster speeds. WhatCable shows you what each cable is actually capable of: its power rating, its data speed, whether it is active or passive, and more The Verge. It also tells you what is happening right now when the cable is plugged in — the actual power flowing through it at this moment The Verge.

How does it work. Every Mac has a chip that manages power when you plug something in. Your Mac already talks to your cables and chargers to figure out how much power is safe to use. WhatCable simply reads that information from your Mac's system data and shows it to you in a clear way The Verge. It does this using only information Apple publicly allows apps to access, with no special behind-the-scenes permissions needed.

The app looks at three things: your Mac's port, whatever you have plugged in, and the cable connecting them GitHub. This matters because a cable is only as good as its weakest link. A super-powerful cable plugged into a lower-power charger will only charge as fast as the charger allows. WhatCable shows you when this mismatch happens.

You can find the code on GitHub at github.com/darrylmorley/whatcable, and the project site is at whatcable.uk The Verge. Morley is also working on a version for Windows, tracked at github.com/darrylmorley/whatcable-windows, though it is not ready yet GitHub.

Until recently, the only way to identify what a cable could do was to buy a separate hardware tester — a small device you would plug the cable into. The Verge covered one about three years ago that cost around $8, but it has since been discontinued The Verge. Those testers could tell you a cable's specifications, but they could not show what was actually happening when you used it. WhatCable does both.

One question worth considering: will WhatCable keep working as Apple updates macOS. It relies on system information Apple has chosen to make public. When Apple updates the system, apps that use private, undocumented information sometimes break. Because WhatCable uses only documented, public information, it has a better chance of staying functional through future updates, though only time will show how well this actually holds up.

The reason USB-C cables are so hard to tell apart is that USB-C was designed to be universal. One connector handles everything from slow data speeds to fast speeds, and from low power to very high power — up to 240 watts with the latest spec. That universality is great for convenience, but it means you cannot tell what a cable does just by looking at it. A software tool that shows you this information without needing to buy extra hardware fits a pattern we have seen before: software keeps replacing gadgets. Phone apps that check battery health replaced standalone battery testers. Network analysis apps replaced dedicated hardware. WhatCable is the latest step in that trend.

For companies managing many Apple computers, a free tool like this could cut down the need for physical cable testers when troubleshooting power and display problems, though no large organization has announced they are using it yet.