WhatCable Utility Identifies USB-C Cable Capabilities and Connection Issues on macOS

USB-C Connection Diagnostics

WhatCable is a new macOS utility designed to provide detailed information about USB-C connections. It reads data from the port, cable, charger, adapter, and connected device to explain the overall performance of the link. This helps users understand why a Mac might be charging slowly or why a display is not performing as expected.

Cable and Device Analysis

The utility can read a cable's e-marker identity, advertised speed, power rating, and active transports. It checks this information against USB Power Delivery rules and compares it with what the Mac has negotiated. WhatCable also identifies USB 2, USB 3, USB4, Thunderbolt, and DisplayPort paths under the physical port.

Identifying Performance Bottlenecks

WhatCable provides a plain-English verdict on what is limiting the connection, whether it's the Mac port, the cable, or the connected device. For charging, it highlights the negotiated power profile and indicates if the cable, charger, or Mac is restricting the current charge rate. For monitors, it shows if the link is carrying the full resolution and refresh rate or if there are limitations from an adapter, the cable, or the selected mode.

Fault Detection and Community Contributions

The utility can detect faults such as overcurrents or connection drops, displaying a banner on the port if issues arise under load. Users can also contribute observations to a public record of how cables identify themselves across different hardware, and search for reported cables by vendor, speed, and identity.