WhatCable

Product Introduction

1. Definition: WhatCable is a macOS menu bar application and command-line interface (CLI) tool designed for USB-C cable and port diagnostics. It is a technical utility that reads and interprets USB Power Delivery (USB-PD) and USB-C e-marker data directly from the macOS IOKit framework.
2. Core Value Proposition: It exists to solve USB-C cable confusion by providing clear, actionable diagnostics. The primary value is eliminating guesswork about why a USB-C cable charges slowly, fails to drive a display, or limits data transfer speeds, directly addressing the universal problem of indistinguishable USB-C cables.

Main Features

1. Cable E-Marker Decoding: WhatCable reads the Vendor Defined Object (VDO) data from a cable's e-marker chip, a small integrated circuit inside certified USB-C cables. It decodes this raw data into plain English, displaying the cable's maximum rated speed (e.g., USB4 40 Gbps), power rating (e.g., 100W, 240W), and vendor identity. This is the foundational technology for identifying cable capabilities.
2. Bottleneck Analysis: The app performs real-time link analysis by comparing the capabilities of the Mac's port, the connected cable, and the attached device (charger, display, SSD). It then highlights the "weak link" in the chain with a plain-English verdict (e.g., "Cable is limiting charging speed" or "Device is limiting data speed"), telling the user exactly which component to upgrade for better performance.
3. Live Power & Negotiation Diagnostics (Pro Feature): WhatCable Pro provides advanced telemetry, including live power metering (watts, amps, volts) updated every 2 seconds and a full PD contract inspector. This shows the complete list of Power Data Objects (PDOs) offered by the power source and the specific voltage/current profile actively negotiated, allowing for deep troubleshooting of charging issues.

Problems Solved

1. Pain Point: The physical uniformity of USB-C connectors masks vast differences in capability (USB 2.0 vs. USB4, 60W vs. 240W). Users cannot visually identify a cable's specifications, leading to poor performance, slow charging, and failed connections for displays or high-speed storage.
2. Target Audience: The primary user personas are Apple Silicon Mac power users (developers, creative professionals, IT support), tech enthusiasts who manage complex desk setups with docks and peripherals, and professionals who rely on consistent, high-speed data transfer and charging for external SSDs, monitors, and hubs.
3. Use Cases: Essential scenarios include: diagnosing why a new 4K monitor won't work with a specific cable; identifying which cable in a drawer supports fast charging for a MacBook Pro; verifying if a purchased "high-speed" cable meets its advertised specifications; and troubleshooting why an external NVMe SSD is performing slower than expected.

Unique Advantages

1. Differentiation: Unlike generic system information tools, WhatCable is purpose-built for USB-C/PD diagnostics on macOS. It surpasses basic "System Report" data by providing interpretation and bottleneck analysis. It differs from hardware cable testers by being a purely software-based, non-invasive solution that uses the Mac's own hardware controllers.
2. Key Innovation: Its core innovation is aggregating and interpreting low-level IOKit data (accessible only on Apple Silicon Macs) into a user-friendly, contextual interface. The "trust signals" feature that flags non-compliant e-marker data (like a zero Vendor ID) and the public cable database built from crowd-sourced user reports are also unique, community-driven approaches to cable verification.

Frequently Asked Questions (FAQ)

1. Does WhatCable work on Intel Macs or Windows? No, WhatCable requires Apple Silicon (M1 or later) Macs running macOS 14 or later. Intel Macs use different Thunderbolt controllers that do not expose the necessary USB-PD and cable e-marker data through public macOS APIs. It is not available for Windows.
2. Can WhatCable definitively detect a fake or counterfeit USB-C cable? Not definitively. WhatCable's "trust signals" feature flags e-marker data that violates the USB-PD specification (e.g., unregistered Vendor ID, reserved bit patterns). This indicates the cable is "worth investigating" or non-compliant, but is not a guaranteed test for counterfeits, as some non-certified cables may still function.
3. Why does my USB-C cable show no e-marker data in WhatCable? Cheap USB 2.0 cables and most cables rated below 3A/60W are not required by the USB-C specification to have an e-marker chip. If a cable lacks this chip, there is no data for WhatCable to read and display. This is normal for basic, low-power charging cables.
4. What is the difference between the free WhatCable app and WhatCable Pro? The free app provides core features: cable identification, bottleneck analysis, and device matching. WhatCable Pro (£4.99 one-time) unlocks 12 advanced features including live power metering, port health counters, full PD contract inspection, DisplayPort Alt Mode details, and raw VDO data for power users and professional diagnostics.
5. Is WhatCable secure, and does it collect my data? According to the developer, WhatCable has no analytics, telemetry, or network calls. It reads only local IOKit data and does not "phone home." The app is open-source (MIT licensed), allowing its code and privacy claims to be publicly verified on GitHub.