About
WhatCable is a diagnostic utility that deciphers the hidden capabilities of USB-C cables.It translates the technical data of the e-marker chip into understandable language, showing real speed, charging and video signal support, and also identifies connection bottlenecks.
All USB-C cables look the same, but some support fast charging and 4K displays, while others only support slow charging and USB 2.0.WhatCable helps you distinguish one from the other without guessing.
Features:
• Diagnostics: Get a verdict on whether your Mac itself, the cable, or the connected device is limiting your charging or data transfer speeds.
• Charging: Sees whether the cable, charger, or Mac is limiting the current.
• Data Speed: Indicates whether a faster cable will help.
• Display Connection: Checks that the cable is outputting the full resolution and refresh rate of the monitor.
• Decoding e-marker data: Shows the declared cable speed (USB 2.0 / USB4 / Thunderbolt), maximum current (3A or 5A), manufacturer information and supported USB Power Delivery profiles.
• Device Identification: Tells you which device (SSD, docking station, peripheral) is connected to which port and what speed it is running at.
• Built-in CLI (command line): Allows you to receive diagnostics in the terminal, including in JSON format for scripts and in --watch mode to monitor changes when connecting cables.
• Cable Trust Signs: Checks e-marker data for compliance with USB-IF specifications and flags suspicious values (null manufacturer ID, reserved bits), indicating possible tampering.
• Live power measurements: Constantly updated watts, amps and volts on every port.
• Complete Negotiation Diagnostics: Compares Mac port, cable, and device support, highlighting the weakest link.
• Advanced Display Diagnostics: Checks if the cable is outputting the full resolution and refresh rate of the monitor (with support for DP Alt Mode and EDID).
• Port health counters: Statistics of resets, errors and FET failures for all time.
• PD Contract Inspector: Complete list of PDOs (power profiles), active voltage/current and mismatch flags.
• Raw VDO data: For developers and advanced users.