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How to use WhatCable, step by step. Requires a Mac with Apple Silicon (M1 or later) running macOS 14+.

Install

WhatCable is signed and verified by Apple, so your Mac won't show any security warnings. You need macOS 14 (Sonoma) or later on a Mac with Apple Silicon (any M1, M2, M3, M4, or M5 chip).

Direct download

Download WhatCable.zip from GitHub, unzip it, and drag WhatCable.app into your Applications folder.

Get the latest release

Homebrew

If you use Homebrew, two commands do everything. This also installs the optional command-line tool. 

brew tap darrylmorley/whatcable
brew install --cask whatcable
Why isn't this on the Mac App Store? The App Store's security sandbox blocks the low-level hardware access WhatCable needs to read cable data. It's still signed and verified by Apple, just distributed outside the store.

Getting started

Open WhatCable from your Applications folder. A small icon appears in your menu bar (the row of icons at the top-right of your screen, near the clock and Wi-Fi).

Click the icon. A panel drops down showing one card for each USB-C port on your Mac.

That's it. No setup, no account, no configuration. Everything updates in real time as you plug and unplug things.

What it shows

Each port card has a headline at the top. This is the quick answer to "what's plugged in here and is it working well?" Here's what each headline means:

When a charger is attached, the headline adds the charger wattage (e.g. "96W charger"). If the cable is the weak link, it adds the cable wattage too, so you can spot the bottleneck at a glance.

Below the headline

Each card shows more detail depending on what's connected:

WhatCable popover showing USB-C port diagnostics: a monitor reached through a USB-C to HDMI adapter with the adapter flagged as the bottleneck, and a 100W charger with the battery full
The main panel. One card per port, showing what's connected and how well it's working.

Common questions

Is my cable any good?

Look at the port card when the cable is plugged in. If the charging and speed info match what you'd expect, the cable is fine. If WhatCable says the cable is limiting speed or charging power, trying a better cable would help. The app tells you exactly what's being held back.

Why is my laptop charging slowly?

Check the charging line on the port card. It tells you what's to blame:

  • "Cable is limiting charging speed" - your cable can't carry the full power your charger offers. A higher-rated cable would fix this.
  • "Charging at 30W (charger can do up to 96W)" - your Mac is choosing to draw less than the charger offers. This is normal when the battery is nearly full or the Mac is idle.
  • "Charging well at 96W" - everything is matched. You're getting the best charge rate this setup can deliver.

What's an e-marker?

A tiny chip inside some USB-C cables that reports the cable's capabilities (speed, power rating, manufacturer) to your Mac. Not all cables have one. Shorter, lower-power cables often don't, and that's completely normal. High-speed cables (Thunderbolt, USB4) and high-power cables (100W and above) always have one.

Do I need a new cable?

Only if WhatCable shows the cable is holding something back. If the charging line says the cable is the bottleneck, a higher-rated cable would help. If everything shows "charging well" or the speed you expect, keep using what you have.

It says "Nothing connected" but I plugged something in

Try unplugging and re-plugging. Some cables and devices take a moment to be recognised. If it persists, the cable might not be making a solid connection, or the device might not identify itself (some simple chargers don't report anything over the data channel).

My Mac mini or Studio front USB-C ports don't show up

On Apple Silicon desktops, the front USB-C ports are standard USB behind an internal hub, not full USB-C ports with their own controller like the ports on the back. The Mac reports no cable, power, or charging data for them, so there's nothing for WhatCable to show. The back Thunderbolt ports work fully.

It says "Basic cable" with no details

This is normal for most everyday USB-C cables. Only higher-rated cables (Thunderbolt, USB4, or cables rated for 100W+) are required to have the chip that reports detailed info. Your cable still works fine, there's just nothing extra to report.

Charging diagnostics

When a charger is connected, WhatCable figures out what's limiting your charge speed and shows it clearly:

Below the charging line, you'll see the charger's power levels: every wattage the charger can supply (e.g. 5V, 9V, 15V, 20V), with the active one highlighted. This is useful for confirming whether a charger actually supports what it says on the box.

Cable trust signals

WhatCable checks a cable's reported data against the official USB specification. When something looks unusual, an orange banner appears with the details. This is not proof that a cable is fake or dangerous. It means something in the reported data doesn't match expectations.

Things that trigger a warning:

If a cable triggers a warning, it might still work perfectly well. Some budget cables use generic chips with placeholder data. The warning is there so you can make an informed decision, not to alarm you.

Notifications

WhatCable can send a notification whenever something is plugged in or unplugged. This is off by default. Turn it on in Settings.

When you enable it, macOS will ask for permission. Notifications are silent (no sound) and show the device name and speed for connections. They work even when the panel is closed.

Settings

Click the gear icon in the top corner of the panel to open Settings.

Behaviour

Display

Notifications

Community

Pro

Right-click (or Control-click) the menu bar icon for quick actions:

Engineer mode

For developers, IT staff, or anyone who wants the raw data: hold Option and click the menu bar icon to show the underlying hardware properties for each port. This includes register values, protocol fields, and the full USB device tree.

You can also turn this on permanently in Settings ("Show technical details"). When a Thunderbolt or USB4 device is connected, this mode also shows the Thunderbolt link tree with per-lane speed and generation info.

WhatCable popover with technical details mode on, showing raw hardware properties below the port card
Technical details mode shows the raw hardware data underneath each port card.

Contribute data

You can optionally submit anonymous hardware data to help WhatCable support more Mac models and cable types. Nothing is collected in the background. A submission only happens when you choose to start one and approve it.

Three ways to start a submission:

Each method shows a consent screen first, explaining exactly what will be sent.

What is sent

What is not sent

Pro features

WhatCable Pro is a one-time purchase that adds deeper diagnostics on top of everything in the free app. All free features stay free forever. Pro adds the following:

Negotiation Diagnostics Pro

The free app gives a one-line summary of what's limiting a connection. Pro shows the full picture: what the Mac port, the cable, and the device each support, side by side with what was actually agreed, with the weak link highlighted. It also cross-checks the cable against the Thunderbolt controller to catch cables that under-report their capabilities. Each screen can pop out into its own window so you can keep it open while you swap cables.

Negotiation Diagnostics screen showing per-port power and data-speed breakdowns with the bottleneck highlighted
Negotiation Diagnostics: what each part of the chain supports vs. what was actually negotiated.

Display Diagnostics Pro

The same weak-link idea, applied to video. WhatCable reads your monitor's capability and its live on-screen mode straight from macOS and compares them against what the DisplayPort link is actually carrying, so a screen stuck below its top resolution or refresh has an explanation you can act on. It shows the monitor's native and top modes, what the link is delivering, the lanes in use against those available, and the link rate. Because it reads the live mode, the resolution is right even on 5K and 6K displays, and when a screen reaches its top mode using compression (DSC) it confirms you're at full quality instead of guessing. If a USB-C to HDMI or DisplayPort adapter is in the chain, it names what the adapter reports itself as, which is often the real cap. It only says "not the cable" when the evidence shows it (a Thunderbolt tunnel, or every lane already in use), and otherwise points at the likely cause without crying wolf, since a shortfall can also just be the mode you have selected.

Display Diagnostics screen showing a monitor's top mode against what the DisplayPort link is carrying, with the adapter named and the shortfall highlighted
Display Diagnostics: what your monitor can do vs what the link is carrying, with the limiting factor named.

Live power metering Pro

Real-time watts, amps, and voltage per port, updated every two seconds. See exactly what your cable is delivering right now, not just what was agreed on paper.

PD contract inspector Pro

See the full power delivery contract your Mac and charger agreed on: the active voltage and current, all available power profiles decoded, and any mismatches flagged.

Cable resistance estimation Pro

Estimates the electrical resistance of your cable in milliohms using real power samples. Useful for spotting worn or marginal cables before they cause problems.

Port health counters Pro

Lifetime stats per port: how many times things have been plugged and unplugged, resets, electrical faults, and other wear indicators. See how a port has been treated over its lifetime.

Pro diagnostics screen showing port health counters, liquid detection status, and the negotiated power contract for one port
Pro diagnostics: port health counters, liquid detection state, and power contract on one screen.

PD event trace Pro

A timeline of what happened when a cable was plugged in: the negotiation steps, any resets, and the final agreement. Useful for diagnosing flaky connections.

DP Alt Mode details Pro

When a monitor is connected over USB-C, see the lane count, link speed, and full display info (model, manufacturer, year). Shows whether the display signal is tunneled through Thunderbolt or running natively.

Pro diagnostics screen for a USB-C port driving a display, showing the device identity and a pin diagram with the DP four-lane routing
Display details: device identity, pin diagram with lane routing, and port health on one screen.

Raw cable identity Pro

The full data that the cable's chip reported, beyond the summary the free app shows. For developers and hardware engineers who need the exact fields.

Liquid detection Pro

Shows whether the moisture sensor inside a USB-C port has been triggered. Useful for diagnosing intermittent charging faults, especially after a spill.

CC advertisement level Pro

Shows what current level the port is advertising to connected devices. A deep diagnostic for power delivery debugging.

Power monitor window Pro

A dedicated window with live charts showing watts and voltage over time. Pin it while you test a charger or cable under load and watch the numbers in real time.

Power Monitor window showing USB-C port 1 drawing 5.9W on a live chart of watts, volts, and amps, with the System Power Input panel below
Power Monitor in its own window, with live per-port watts, volts, and amps. On Macs without live per-port draw, the value shown is the negotiated maximum instead.

CLI monitor mode Pro

whatcable --monitor streams live power and cable state to your terminal. whatcable --monitor-json outputs the same data as JSON for scripting.

Widget power sparkline Pro

The desktop widget shows a live power chart alongside cable status. Glance at your desktop and see charging trends without opening anything.

Activate Pro: right-click the WhatCable icon in the menu bar and click Licence. Paste your key and click Activate. Works on up to 2 Macs. See the Pro page for pricing.

Troubleshooting

My cable shows as "Basic cable"

This is normal for most everyday USB-C cables. Only higher-rated cables (Thunderbolt, USB4, or cables rated for 100W+) are required to have a chip that reports detailed information. Your cable still works, there's just nothing extra to read.

Some cables do have the chip, but macOS only reads it when the connection needs the cable's identity: a charge drawing more than 3A (a 5A cable on a high-wattage charger), or a Thunderbolt / USB4 link. On a low-power charger or a plain data connection, macOS may never query the chip, so there's nothing to show even though the cable is marked. Try plugging in a higher-wattage charger (60W or above), or connect it to a Thunderbolt device, and check again.

Vendor shows as "Unregistered / unknown"

WhatCable looks up manufacturer names from the official USB industry list, which is bundled with the app. If the name isn't showing, it means the manufacturer either isn't registered or registered after this version of the app was built. It doesn't mean the cable is fake. The list is updated with each app release.

Doesn't work on my Intel Mac

WhatCable only works on Macs with Apple Silicon (M1, M2, M3, M4, M5). Intel Macs use a different USB-C controller that doesn't expose the cable data WhatCable reads. There's no workaround for this.

I can't see the icon in the menu bar

If your menu bar is full, macOS may hide the icon behind the notch or other apps. Try closing some menu bar apps, or switch WhatCable to Dock mode in Settings if space is tight.

Notifications aren't showing up

Check two things. First, make sure notifications are turned on in WhatCable's Settings. Second, go to macOS System Settings > Notifications > WhatCable and make sure alerts are allowed. If you clicked "Don't Allow" when first asked, you'll need to re-enable it here.

"Report this cable" isn't showing any data

The report feature needs data from the cable's chip to work. If no data was read, there's nothing to report. This happens when the cable doesn't have a chip (see "Basic cable" above) or macOS hasn't queried it yet. Try a higher-wattage charger (60W+) to trigger the read.

App opens but nothing appears

If you launch WhatCable and nothing shows up (no menu bar icon, no window), try these steps in order:

  1. Check the menu bar. The icon may be hidden behind the notch or other apps. Try closing a few menu bar apps and relaunching WhatCable.
  2. Quit and relaunch. Open Activity Monitor, search for "WhatCable", force-quit it if it's running, then open it again from Applications.
  3. Try the CLI. Open Terminal and run whatcable. If that prints port data, the hardware access is working and the issue is with the menu bar UI. Include the CLI output when filing a bug report.
  4. Collect diagnostic logs (see below) and include them in a bug report.

Collecting diagnostic logs

WhatCable logs key startup steps to the macOS system log. If the app isn't behaving as expected, these logs help us figure out where it gets stuck. To capture them:

  1. Quit WhatCable if it's running.
  2. Open Terminal (in Applications > Utilities).
  3. Paste this command and press Enter:
    log stream --predicate 'subsystem == "uk.whatcable.whatcable"'
    You'll see "Filtering the log data..." and then it waits.
  4. Open WhatCable from your Applications folder.
  5. Wait a few seconds. Log lines will appear in Terminal showing what the app did during launch.
  6. Copy everything that appeared and include it in your bug report.

Press Ctrl+C in Terminal to stop the log stream when you're done.

Widget not appearing after an update

If the desktop widget disappears after updating WhatCable (especially via Homebrew), macOS may have stale references to the old version. This was fixed in v0.14.1, which re-registers the widget on every launch. If you're on 0.14.1 or later and the widget is still missing:

  1. Right-click the desktop, choose Edit Widgets, and remove the WhatCable widget.
  2. Quit and relaunch WhatCable.
  3. Add the widget again from the widget gallery.

Good to know