Developer Darryl Morley presented WhatCable, a small macOS menu-bar application designed to describe what a connected USB-C cable can do. The project addresses a persistent usability problem: cables with the same connector can support dramatically different charging power, data rates and display capabilities while offering few visible clues about those differences.
WhatCable reads information that macOS already exposes through IOKit and converts it into a more approachable summary. The project's documentation says it can surface cable speed and power characteristics and help explain why a Mac may be charging more slowly than expected. Its decoding follows the USB Power Delivery specification identified in the repository as USB-PD 3.2 version 1.2.
The application is free and open source, while a paid Pro upgrade adds live power monitoring, connection-negotiation and display diagnostics, plus a history of saved cables. Those features are aimed at finding the limiting component in a setup and retaining evidence of how a cable performed. The licence is described as a one-time purchase usable on as many as two Macs.
Compatibility is narrower than the universal USB-C connector might suggest. WhatCable requires macOS 14 Sonoma or later and an Apple Silicon Mac. The developer says community diagnostics from Intel Macs showed that the public IOKit interfaces did not expose the USB-C port-controller state and e-marker data on which the utility depends, even though Thunderbolt fabric information remained available.
Users can install the signed and Apple-notarised application manually or through the project's Homebrew tap. It is distributed outside the Mac App Store because, according to the documentation, the sandbox blocks the system-management-controller access needed for Pro power measurements and does not fit the bundled command-line tool's installation model. A separate CLI-only Homebrew package is also available.
The command-line program uses the same diagnostic engine and can produce machine-readable JSON, making it useful for scripts as well as interactive troubleshooting. The repository says the software uses no private APIs, special entitlements or helper daemons. Ordinary inspection happens locally and does not automatically transmit cable information. If a user chooses the "Report this cable" function, the app prepares a GitHub issue containing identifiers and capability flags, opens it in a browser and leaves submission to the user.
WhatCable cannot diagnose every charging problem. Its own documentation separates cable and negotiated-power details from battery condition, which is handled by a companion utility. Within that boundary, it offers a practical way to turn otherwise obscure connection metadata into information a Mac owner can act on.
