We’ve talked on a number of occasions about the problem with USB‑C cables: they all look alike but can have very different capabilities. Google addressed this issue in Chrome OS several years ago, and we suggested at the time that Apple should copy it. That hasn’t yet happened, but there’s now a free Mac app, WhatCable, to turn your Mac into a hardware cable tester …\n\nWhatCable works by measuring what the cable is delivering while it’s actually in use, or by looping it from one USB‑C port on your Mac to another.

It can also read the identifier in the embedded chip to determine the vendor and whether it is USB‑IF certified. The app provides a plain‑English verdict on what is limiting the link—whether it’s the Mac port, the cable, or the device—and shows whether a monitor is getting its full resolution and refresh rate. It decodes cable speed, current rating, vendor identity, and USB‑PD capability flags, highlighting limits such as a 40Gb/s data‑transfer ceiling.

It also shows whether the charger or the Mac is limiting the current charge rate, with the negotiated power profile highlighted, so you know if a faster cable would actually help.\n\nThe free version offers the core features, while the Pro version adds a live negotiation breakdown for a one‑off fee of £9.99 (around $13.40). The Verge’s Sean Hollister tested it and found it performed well, though some cables may lie about their capabilities. The interface is straightforward, presenting all information in clear language without requiring technical expertise.

The app uses income‑earning auto affiliate links, as noted in the FTC disclosure.