whatcable

whatcable answers a question macOS hides: what can this USB-C cable actually do? Plug a charger or peripheral into a Mac, and the menu bar tells you the cable's real specs (USB 2.0 vs 5/10/20/40/80 Gbps), its power rating (3A or 5A up to 60W/100W/240W), and why charging might be slower than expected. MIT licensed, free.

The data already exists in macOS via IOKit. whatcable surfaces it. No private APIs, no kernel extensions, no daemons. Install via Homebrew (`brew install --cask whatcable`) or grab the signed and notarized .app from GitHub Releases. Apple Silicon only, macOS 14 or later. The "why is my Mac charging slowly" diagnostic is the killer feature. It tells you whether the cable, the charger, or the Mac itself is the bottleneck.

This is a niche utility. If you have a drawer of identical-looking USB-C cables and one of them is silently a USB 2.0 charge-only cable, you have already needed this. Free, no paid tier, single-developer maintenance.

The catch: Apple Silicon only. Intel Macs use older Thunderbolt controllers that do not expose the PD state and cable e-marker data the app reads.