WhatCable explains cable speed, charging limits, e-marker data, and connected devices in plain English. No more guessing why a cable charges slow or refuses to drive your display.
Your drawer is full of identical-looking cables. Some charge at full speed, some crawl. Some carry video, some can barely handle a mouse. The connector tells you nothing.
Charges slowly, no video output. Fine for a keyboard, terrible for an external display or fast storage.
Fast data, good charging. Handles most displays and external SSDs without issues.
Full speed data, maximum charging, dual 4K displays. The cable your dock needs but you cannot tell by looking.
WhatCable reads the USB-C and USB Power Delivery details macOS already exposes, then turns them into useful labels, charging diagnostics, and port-by-port device context.
See whether the cable, charger, or Mac is limiting the current charge rate, with the negotiated power profile highlighted.
Decode cable speed, current rating, vendor identity, and USB PD capability flags from marked USB-C cables.
Identify USB 2, USB 3, USB4, Thunderbolt, and DisplayPort paths under the physical port where they are connected.
Option-click or enable raw details to reveal the underlying IOKit properties when you need the registry-level facts.
Match storage, hubs, docks, and peripherals back to the port they are using, including the negotiated USB speed.
A focused menu bar app on Apple Silicon Macs. No helper daemon, no private API, no background uploads.
The bundled CLI gives you quick snapshots, structured JSON for scripts, and watch mode when you are swapping cables during testing.
jq for repeatable diagnostics.
--watch.
$ whatcable USB-C Port 1 ✓ Charging well at 96W Cable: 5A, 100W, USB4 40 Gbps Charger: 5V / 9V / 15V / 20V PDOs USB-C Port 2 ! Cable is limiting charging speed Cable: 3A, 60W, USB 2.0 Device: External SSD, USB 10 Gbps
WhatCable checks the e-marker data against the USB Power Delivery spec. When something looks unusual, an orange card appears with the details. It is not a guarantee the cable is fake, but it tells you where to look.
WhatCable stays out of the way until you need it. A few settings let you control how it runs and what it shows.
Get alerts when cables connect or disconnect.
Run as a regular window instead of a menu bar icon.
Start automatically so it is ready when you plug in.
Only show ports with something plugged in.
No. Intel Macs use Titan Ridge Thunderbolt controllers that don't expose USB-PD state or cable e-marker data through any public macOS API. WhatCable needs Apple Silicon (M1 or later) to read this information.
Yes. WhatCable is open source under the MIT licence. No ads, no tracking, no in-app purchases.
No. There are no analytics, no telemetry, and no network requests. The app reads local IOKit data and nothing else. Check the source on GitHub if you want to verify.
Cheap USB 2.0 cables and most cables rated under 3A don't have an e-marker chip. WhatCable can only show what the cable reports. If there is no chip, there is no data to decode.
Not definitively. The trust signals feature flags values that look unusual against the USB-PD spec, like a zero vendor ID or reserved bit patterns. A flag means "worth checking," not "definitely counterfeit."
WhatCable is signed, notarised, and ships as a universal app. Requires macOS 14 or later on Apple Silicon.
brew tap darrylmorley/whatcable brew install --cask whatcableView tap on GitHub
Grab the latest .zip from GitHub Releases. Drag WhatCable.app into Applications.