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darrylmorley/whatcable

A macOS menu bar app that explains in plain English what each USB-C cable on your Mac can do and why charging may be slow.

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What is it?

USB-C uses one connector for everything from USB 2.0 charge-only cables to 240W Thunderbolt 4 cables, which look identical. WhatCable reads the port, charger, device and cable data that macOS exposes through IOKit and shows it as a popover per port. It reports the cable's speed and current rating, the charger's voltage profiles, the negotiated power, and which part of the chain is the bottleneck.

Beyond charging, it decodes Thunderbolt and USB4 fabric, active transports, connected devices (with hubs hidden by default), and cable e-marker data including brand and model for cables in its bundled database. A CLI shares the same engine and offers JSON output, watch mode and raw IOKit dumps.

WhatCable requires macOS 14 or later on Apple Silicon. Some diagnostics and dashboards are part of an optional paid Pro tier, while the core menu bar app and CLI are free and open source under a permissive license.

Key features

  • 01Shows per-port headline status such as charging only, USB device, or Thunderbolt / USB4.
  • 02Diagnoses charging bottlenecks, such as a cable rated below the charger.
  • 03Displays cable speed, current rating and chip vendor from the e-marker.
  • 04Lists every voltage profile the charger advertises, highlighting the negotiated one.
  • 05Shows Thunderbolt lanes, generation and switch topology for multi-hop docks.
  • 06Provides a CLI with JSON output and watch mode.

Use cases

  • Working out why a Mac charges slowly after switching to a new cable or charger.
  • Checking whether a cable supports Thunderbolt or 40 Gbps data before buying a dock.
  • Diagnosing a USB device or dock that runs slower than expected.
  • Scripting USB-C port checks from the terminal with the CLI's JSON output.

Quick start

  1. 1

    Install the menu bar app with Homebrew

    brew install --cask darrylmorley/whatcable/whatcable
  2. 2

    Or install only the command-line tool

    brew install darrylmorley/whatcable/whatcable-cli
  3. 3

    Run the CLI to see a summary of every port

    whatcable

Things to know

  • Apple Silicon Macs only; Intel Macs do not expose the needed USB-C port data.
  • Requires macOS 14 (Sonoma) or later.
  • Some advanced features (live power metering, diagnostics, dashboard) require a paid WhatCable Pro licence.

Topics

#macos#usb-c#thunderbolt#iokit#menubar-app#swift#swiftui#hardware-info#apple-silicon#mac-app

FAQ

What is whatcable?
A macOS menu bar app that explains in plain English what each USB-C cable on your Mac can do and why charging may be slow. USB-C uses one connector for everything from USB 2.0 charge-only cables to 240W Thunderbolt 4 cables, which look identical. WhatCable reads the port, charger, device and cable data that macOS exposes through IOKit and shows it as a popover per port. It reports the cable's speed and current rating, the charger's voltage profiles, the negotiated power, and which part of the chain is the bottleneck.
Is whatcable free to use? What license does it have?
whatcable is open source under the Other license. Check the license terms before using it in commercial products.
Is whatcable still maintained?
Actively maintained. The last commit to whatcable was on Oct 13, 2026.
What can I use whatcable for?
Working out why a Mac charges slowly after switching to a new cable or charger. Checking whether a cable supports Thunderbolt or 40 Gbps data before buying a dock. Diagnosing a USB device or dock that runs slower than expected. Scripting USB-C port checks from the terminal with the CLI's JSON output.
How do I install whatcable?
Install the menu bar app with Homebrew: brew install --cask darrylmorley/whatcable/whatcable Or install only the command-line tool: brew install darrylmorley/whatcable/whatcable-cli Run the CLI to see a summary of every port: whatcable
Where can I get whatcable?
The source code and installation instructions are on GitHub: https://github.com/darrylmorley/whatcable

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