What can this USB-C cable actually do? A small macOS menu bar app that tells you, in plain English, what each USB-C cable plugged into your Mac can actually do, and why your Mac might be charging slowly . USB-C hides a lot under one connector. Anything from a USB 2.0 charge-only cable to a 240W / 40 Gbps Thunderbolt 4 cable, all looking identical in your drawer. macOS already exposes the relevant info via IOKit; WhatCable surfaces it as a friendly menu bar popover. What it shows Per port, in plain English: At-a-glance headline — Thunderbolt / USB4, USB device, Charging only, Slow USB / charge-only cable, Nothing connected Charging diagnostic — when something's plugged in, a banner identifies the bottleneck: "Cable is limiting charging speed" (cable rated below the charger) "Charging at 30W (charger can do up to 96W)" (Mac is asking for less, e.g.…