WhatCable Pro — Mac download

WhatCable Pro is a macOS utility that decodes the hidden capabilities stored inside a USB-C cable's e-marker chip.

Power Monitor — live voltage, current, and wattage with mismatch flags when a charger under-delivers.

Speed Check — reports which device is attached to which port and the exact data rate it negotiated.

Bottleneck Finder — identifies whether the Mac, the cable, or the connected device is limiting the connection.

PD Contract Inspector — lists PDOs, active voltage, and flags mismatches between what the charger offers and what the cable can carry.

E-Marker Validation — checks e-marker data against USB-IF specifications and flags suspicious values.

Raw VDO Data — exposes the full Vendor Defined Objects for developers and advanced users who need to verify firmware claims.

Negotiation Diagnostics — a side-by-side comparison of Mac, cable, and device support, including charging and video signal compatibility.

How WhatCable Pro compares

WhatCable Pro vs. System Information — Apple's built-in System Information shows you the negotiated speed of a connected USB device, but it stops there. It cannot decode e-marker data, map Power Delivery profiles, or flag a cable that quietly caps your charger. Think of System Information as a label reader and WhatCable Pro as a full inspection report. Both have their place. Only one answers why a connection is slow.

WhatCable Pro vs. USB-C hardware testers — dedicated USB-C testers from brands like ChargerLab or FNIRSI decode e-marker chips and measure voltage and current. WhatCable Pro covers the same ground from the menu bar, no extra hardware required. A hardware tester works with any device; the Mac app works only with what your Mac can see. For most Mac users, that is enough. You get live measurements, PD contract details, and cable validation without carrying another gadget.

WhatCable Pro vs. IORegistryExplorer — Apple's developer tool exposes raw USB and Thunderbolt data, including some VDOs. That approach suits engineers who enjoy reading hex dumps. WhatCable Pro translates the same raw data into readable fields, adds validation against USB-IF specs, and includes a --watch mode for testing cables as you swap them. If you already know how to parse IORegistry, the app's command-line interface and JSON output still save time.

When a 4K Monitor Stubbornly Drops to 30 Hz

The app earns its place on a few specific desks.

• Mac users with docks and multi-display setups — when a 4K monitor refuses to run at 120 Hz or drops to USB 2.0 speeds, WhatCable Pro shows whether the cable, the dock, or the Mac negotiated the lower spec.
• Field technicians and IT support staff — fault-finding a charger or cable becomes a two-minute read instead of trial and error. The JSON output fits into existing diagnostic scripts.
• Power users with a cable drawer — many people own ten USB-C cables and trust none of them. Saved Cables lets you label and compare e-marker data so the 60 W cable stops going into the travel bag with a 100 W charger.
• Developers and hardware reviewers — raw VDO data and PD contract details make it easier to verify what a cable actually advertises, not what the packaging claims.

If your USB-C problems are rare and simple — one Mac, one charger, one cable — the free features of macOS may be enough. Once you start juggling docks, monitors, chargers, and external drives from different brands, a tool that reads the cable itself saves real time. That is where the download WhatCable Pro for Mac option becomes the practical choice rather than a curiosity.

• macOS 14 or later
• Apple Silicon or Intel 64-bit