What is WhatCable?

WhatCable is a macOS utility that reads USB-C and USB Power Delivery data already exposed by your Mac and translates it into plain-English explanations. Instead of guessing why a cable charges slowly or fails to drive a display, WhatCable shows you cable speed, charging power, e-marker data, and connected devices in clear, actionable language. The free app identifies bottlenecks—whether the cable, charger, or Mac is limiting performance—and the optional Pro version adds live power metering, port health tracking, and raw VDO diagnostics.

Who it's for

• Mac users with mixed cable drawers – Anyone who owns multiple identical-looking USB-C cables and wants to know which one supports fast charging, video output, or high-speed data without trial and error.
• Power users and IT troubleshooters – Professionals who need to diagnose charging issues, verify cable specs against USB PD standards, or script cable testing with the bundled CLI tool.
• Apple Silicon Mac owners – Users with M1 or later Macs who want a lightweight, open-source app that reads USB-PD state and e-marker data without background uploads, private APIs, or daemon processes.

Key features

Plain-English charging diagnostics

WhatCable tells you whether the cable, charger, or Mac is limiting the current charge rate, with the negotiated power profile highlighted. A clear verdict explains if a faster cable would actually help or if the bottleneck lies elsewhere.

Cable and port identification

Decode cable speed, current rating, vendor identity, and USB PD capability flags from marked USB-C cables. The app identifies USB 2, USB 3, USB4, Thunderbolt, and DisplayPort paths under the physical port where they are connected, matching storage, hubs, docks, and peripherals back to their port.

E-marker verification and public database

WhatCable checks e-marker data against the USB Power Delivery spec and flags unusual readings with an orange card. Every reported cable is added to a public, searchable database so you can check if your cable has been seen before or browse what others are using.

Menu bar convenience with optional Pro upgrade

The app stays out of the way until needed, running as a menu bar icon with settings for auto-start, alerts on connect/disconnect, and window mode. Pro (£4.99 one-time, up to 2 Macs) unlocks live power metering, port health counters, PD contract inspection, and raw VDO fingerprints.

What stands out

WhatCable turns cryptic USB-C registry data into a one-line verdict: "Charging well at 96W" or "Cable is limiting charging speed."

This is the core differentiator. While other tools dump raw IOKit properties or require deep USB PD knowledge, WhatCable surfaces the exact bottleneck in plain English. The free open-source app (MIT licence, no tracking) gives you cable speed, charging limits, and device context without a subscription, and the optional Pro upgrade adds professional diagnostics for a one-time fee.

Worth checking out if…

You own an Apple Silicon Mac and a drawer full of USB-C cables that all look the same. Whether you're troubleshooting a slow-charging laptop, verifying a cable for a high-resolution display, or simply want to know which cable supports USB4 40 Gbps, WhatCable removes the guesswork. It's also ideal for IT teams who need repeatable cable testing via the CLI tool or want to contribute to the public cable database.