WhatCable: Know what your USB-C cable can really do

As featured in

“Finally tells you what your USB-C cables can actually do.”

Brady Snyder, MakeUseOf

Answers, not raw data<br>See what is happening across the whole connection.

A cable never works alone. WhatCable reads the port, cable, charger, adapter and connected device together, then explains the result in plain English.

Charging<br>Why is this Mac charging slowly?

See what the charger offers, what the cable supports, and whether the Mac is drawing all the power it needs. WhatCable explains the result instead of leaving you to swap components at random.

Charger and cable are fine. The Mac will draw up to 94W when it needs to.

Cable identity<br>What kind of cable is this?

Read the cable's e-marker identity, advertised speed, power rating and active transports. Turn on technical details when you need the underlying values from macOS.

USB4 Gen 4 at 80 Gbps. Rated for up to 240W.

How WhatCable knows<br>Claims are useful. Observed behaviour is better.

WhatCable reads the identity a cable reports, checks it against USB Power Delivery rules, and compares it with what the Mac actually negotiated. It cannot see inside the cable jacket and never pretends it can.

Contributed observations build a public record of how real cables identify themselves across real hardware.

125<br>cable observations in the public database

Reported through WhatCable<br>Searchable by vendor, speed and identity<br>Nothing is uploaded without your action

Cables seen by WhatCable users.

Search reported cables by vendor, speed and identity, or see whether yours has appeared before.

Browse all cables

USB4 80 GbpsCalDigit TB5 cable 240W, passive

USB 2.0Anker 333 nylon 100W, passive

USB 3.2 Gen 2Monoprice Essentials 100W, passive

Features<br>Plain answers for cables that all look the same.

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.

Charging bottlenecks<br>See whether the cable, charger, or Mac is limiting the current charge rate, with the negotiated power profile highlighted.

Mid-session fault warnings<br>If a cable develops trouble while it is plugged in (an overcurrent or the connection dropping and reconnecting), a banner appears on the port. Catches faults that only show up under load.

Data-speed bottlenecks<br>A plain-English verdict on what is limiting the link: the Mac port, the cable, or the device, so you know whether a faster cable would actually help.

Display bottlenecks<br>When a monitor is connected, see whether the link is carrying its full resolution and refresh, or falling short, and whether an adapter, the cable, or the selected mode is the limit.

Cable e-marker data<br>Decode cable speed, current rating, vendor identity, and USB PD capability flags from marked USB-C cables, including USB-IF certification read straight off the cable.

Active transports<br>Identify USB 2, USB 3, USB4, Thunderbolt, and DisplayPort paths under the physical port where they are connected.

Engineer mode<br>Option-click or enable raw details to reveal the underlying IOKit properties when you need the registry-level facts.

Connected devices<br>Every device sits inside the thing it is actually plugged into, not a flat pile. Hubs are hidden by default, and each device says how many it is sitting behind.

Built for macOS<br>A focused menu bar app on Apple Silicon Macs. No helper daemon, no private API, no background uploads.

Check your cables on the Mac you already use.<br>Free, open source, and available in 19 languages.

Download WhatCable for free

CLI<br>The same diagnostic engine in your terminal.

The bundled CLI gives you quick snapshots, structured JSON for scripts, and watch mode when you are swapping cables during testing.

Readable summaries for quick cable checks.

Pipe JSON into jq for repeatable diagnostics.

Live updates as ports connect and disconnect with --watch.

Full-screen live dashboard of ports, power, and Thunderbolt with --dashboard (Pro).

~ whatcable

$ whatcable

USB-C Port 1<br>✓ Charging well at 96W<br>Cable: 5A, 100W, USB4 40 Gbps<br>Charger: 5V / 9V / 15V / 20V PDOs

USB-C Port 2<br>! Cable is limiting charging speed<br>Cable: 3A, 60W, USB 2.0<br>Device: External SSD, USB 10 Gbps

Cable trust signals<br>Spot cables that don't add up.

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.

Vendor ID checked against the USB-IF published list.

Speed and current fields validated against PD spec ranges.

Reserved bit patterns and zero-value metadata flagged.

Cable trust flags

Vendor ID is 0x0000 (not registered with USB-IF)

Cable latency field uses a reserved value

Claims 5A current but reports USB 2.0 speed

Settings<br>Make it yours.

WhatCable stays out of the way until you need it. A few settings let you control how it runs and...