whatcable

WhatCable is a small macOS menu bar app that reads your Mac's USB-C port state via IOKit and explains, in plain English, what each connected cable can actually do. It shows per-port headlines like Thunderbolt/USB4, USB device, Display connected, Charging only, or Slow USB/charge-only cable, plus charging diagnostics that identify whether the cable, charger, or Mac is limiting charging speed. It also reports data-speed verdicts, cable e-marker specs (speed, current rating, vendor), USB-IF certification status, charger PDO lists, connected device identity, Thunderbolt fabric details (per-lane speed, generation, topology), and active transports. A trust-signals card flags unusual e-marker values without declaring a cable fake. The app includes desktop WidgetKit widgets, a CLI (`whatcable`) with human-readable, JSON, watch, and raw output modes, and a Pro tier (paid) adding cable history, live power metering, negotiation and display diagnostics, a terminal dashboard, and more. It is free and open source (MIT), requires macOS 14+ and Apple Silicon, and is signed and notarised. Installation is via direct download or Homebrew (app or CLI-only cask). It reads only from IOKit, no private APIs or helper daemons, and sends nothing automatically; opt-in diagnostic data contribution and update checks via GitHub Releases API. The project also links to companion apps WhatBattery and WhatPort, and a community Rust port for Linux called usbeehive.