Free macOS App WhatCable Replaces Hardware USB-C Cable Testers

Darryl Morley released WhatCable, a free menu-bar utility for Apple Silicon Macs that reads USB-C cable specifications and live power-delivery negotiation data directly from macOS IOKit via public APIs, without hardware dongles or root access. The app cross-references three data sources—the Mac's port, the connected device, and the cable—to surface e-marker profiles and real-time voltage and current. A hardware USB-C tester with LED indicators, reviewed three years ago, has since been discontinued, exemplifying software's ongoing displacement of niche diagnostic gadgets.