technology
Free Mac app displays USB-C cable specifications from system data
WhatCable reads port controller information on Apple Silicon Macs to show cable speed, power, and connection details. The free tool also measures actual negotiated speeds and power delivery during use.
Jul 13, 7:58 AM·1m read1 source
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A free Mac application called WhatCable shows detailed information about connected USB-C cables by reading data already stored in the system. The program displays vendor identification, speed rating, current rating, voltage limits, and whether a cable is active or passive. It also reports the actual connection speed and power levels measured by the computer.
How the application works Creator Darryl Morley said the software accesses information from the port controller chip that handles USB Power Delivery negotiation. The chip sends a message to cables containing an e-marker and receives structured data that macOS stores in the IOKit registry.
WhatCable reads this registry using public application programming interfaces without requiring additional access privileges.
Testing results Tests showed one cable advertised as supporting 10 Gbps data transfer but limited to slower speeds in practice. Another cable reported 10 Gbps capability in its e-marker data while actual transfers occurred at 480 Mbps. A third cable displayed accurate 100-watt charging capability and 480 Mbps data transfer rates that matched its specifications.
Morley said a paid Pro version adds real-time power monitoring and diagnostic tools for £9.99. A simpler companion application called WhatPort shows current activity at each port. Morley stated that hardware differences prevent development of a Windows version and that Android and iOS do not provide sufficient low-level access.
A Linux version is in development.
