What can this USB-C cable actually do?

Website: whatcable.uk (overview, screenshots, and CLI docs)

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.

Part of a family: WhatBattery for battery health and charging, WhatPort for every port at once.

Per port, in plain English:

• At-a-glance headline: Thunderbolt / USB4, USB device, Display connected, 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. battery near full)
  • "Charging well at 96W" (everything matches)
  • "Battery full, not charging" (plugged in, battery full, so the Mac isn't drawing power)
• Mid-session fault warnings: if a cable develops trouble while it's plugged in (a power overcurrent, or the connection dropping and coming back), a banner appears on the port. It reads the port's own fault counters, so it catches faults that only show up once a cable is under load.
• Data-speed diagnostic: a plain-English verdict on what's limiting the link, the Mac port, the cable, or the device. For example "Cable is limiting data speed", "Device runs at 10 Gbps, this is the fastest it supports, not a cable problem", or "Running slower than expected" when the link came up degraded. Shown inline, in the CLI, and in JSON.
• Cable e-marker info: the cable's actual speed (USB 2.0, 5 / 10 / 20 / 40 / 80 Gbps), current rating (3 A / 5 A up to 60W / 100W / 240W), and the chip's vendor
• USB-IF certification: