A Bitmoor product macOS menu bar diagnostics for USB-C
Plug in a cable. WhatCable shows its speed, power capability, display path, and the weak link in your connection, using what macOS reports, not what the packaging promises.
Need deeper diagnostics? Explore WhatCable Pro
Open source, Pro optional Apple Silicon, macOS 14+ Signed and notarised Available in 19 languages
Answers, not raw data
A cable never works alone. WhatCable reads the port, cable, charger, adapter and connected device together, then explains the result in plain English.
Charging
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
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
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 cable observations in the public database
Reported through WhatCable Searchable by vendor, speed and identity Nothing is uploaded without your action
Search reported cables by vendor, speed and identity, or see whether yours has appeared before.
USB4 80 GbpsCalDigit TB5 cable240W, passive
USB 2.0Anker 333 nylon100W, passive
USB 3.2 Gen 2Monoprice Essentials100W, passive
Features
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.
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.
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.
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.
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.
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.
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.
A focused menu bar app on Apple Silicon Macs. No helper daemon, no private API, no background uploads.
CLI
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.--dashboard (Pro).$ 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
Cable trust signals
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.
Settings
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.
Pro
The free app answers the everyday questions. Pro adds history, live measurements, and the deeper evidence needed for difficult faults and repeat testing.
£9.99 one-time. Works on up to 2 Macs.
Cable historyAdd a cable, give it a name, and WhatCable records how it performs over time, with a verdict per cable.
Negotiation DiagnosticsMac port, cable, and device support side by side, with the weak link highlighted.
Live power meteringWatts, amps, and voltage per port, updating every 2 seconds.
No. WhatCable needs Apple Silicon (M1 or later). This is measured, not assumed: every Intel Mac in our community diagnostic data reports its USB-C port controllers as empty, so the USB-PD state and cable e-marker data WhatCable is built on never appear on those machines at all. Thunderbolt link data is still there on Intel, but the port-controller layer WhatCable reads is not.
Yes. The WhatCable app is free and open source under the MIT licence. No ads, no tracking. WhatCable Pro (£9.99, optional) adds advanced diagnostics for power users. See what's included.
Pro unlocks 16 advanced features including cable history (named cables with a recorded timeline), live power metering, Negotiation and Display Diagnostics, port health counters, PD contract inspection, and raw VDO identity. One-time £9.99, no subscription, works on up to 2 Macs. See full features and comparison.
No analytics, no telemetry, and nothing about you or your cables ever leaves your Mac. In the free app the one routine network call is a version check against the public GitHub Releases API, roughly every 6 hours. WhatCable Pro adds one more: a licence check when you activate your key, then once each time the app launches. That call sends only the key and your Mac's hardware UUID, which is how the two-Mac limit is enforced. Diagnostic data only goes anywhere if you explicitly choose to contribute it. Check the source on GitHub if you want to verify.
Not only. On a plain USB connection the cable's e-marker chip is all macOS exposes, so that is what WhatCable shows. But on a Thunderbolt or USB4 connection it goes further: it reads the speed the Mac's controller actually negotiated with the cable and shows it next to the e-marker's claim, so a cable that under-reports itself is caught. The measured speed is a floor, meaning at least this fast, so a genuine 10 Gbps cable that never forms a Thunderbolt link really is 10 Gbps.
Two reasons. Either the cable has no e-marker chip (cheap USB 2.0 cables and many cables rated at 3A or below don't have one), or it has a chip but macOS hasn't read it. macOS only asks a cable to identify itself when the connection needs it: a charge drawing more than 3A (a 5A cable on a high-wattage charger), or a Thunderbolt / USB4 link. Plug a marked cable into a low-power charger or a plain data connection and macOS may never query it, so there's nothing for WhatCable to show. To force the read, connect the cable to a high-wattage charger or a Thunderbolt device.
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."
19, and the diagnostic verdicts are translated too, not just the menus: Armenian, Brazilian Portuguese, Dutch, English, French, German, Hindi, Italian, Japanese, Korean, Latvian, Norwegian, Polish, Russian, Simplified Chinese, Spanish, Traditional Chinese, Turkish, and Ukrainian. WhatCable follows your Mac's language by default, or you can pick one in Settings. Translations are community-refinable, so if something reads oddly in your language, open an issue and we'll fix it.
Install
Menu bar app, command-line tool, or both. Signed, notarised, and universal. Requires macOS 14 or later on Apple Silicon.
Menu bar app plus the whatcable CLI on your PATH.
brew install --cask darrylmorley/whatcable/whatcable
Just the whatcable command, no menu bar app. Same signed binary, useful for terminal-only setups and scripts.
brew install darrylmorley/whatcable/whatcable-cli
Grab the latest .zip from GitHub Releases. The release page also has a CLI-only zip. Drag WhatCable.app into Applications.
The rest of the answer
Knowing a charger only negotiated 60W raises the next question, and it is usually about the battery or the port it is plugged into. Two more Mac utilities from the same developer, built the same way: read what the Mac already knows, then say it in plain English.