Docs

How to use the WhatCable menu bar app. Requires macOS 14+ on Apple Silicon.

What it shows

WhatCable sits in your menu bar. Click the icon to see a popover with one card per USB-C port on your Mac. Each card shows, in plain English:

• Headline: Thunderbolt / USB4, USB device, Charging only, Slow USB / charge-only cable, or Nothing connected.
• Charging diagnostic: whether the cable, charger, or Mac is the bottleneck, with the negotiated wattage.
• Cable e-marker info: the cable's actual speed (USB 2.0 up to 80 Gbps), current rating (3A or 5A), and the e-marker chip vendor.
• Charger PDO list: every voltage profile the charger advertises (5V, 9V, 15V, 20V, etc.), with the active one highlighted.
• Connected device: vendor name and product type from the PD Discover Identity response.
• USB devices: storage, hubs, and peripherals listed under the port they are plugged into, with their negotiated speed.
• Active transports: USB 2, USB 3, Thunderbolt, and DisplayPort paths.

Charging diagnostics

When a charger is connected, WhatCable identifies the bottleneck and shows a banner:

• "Charging well at 96W" means the cable, charger, and Mac are all matched.
• "Cable is limiting charging speed" means the cable is rated below what the charger can deliver.
• "Charging at 30W (charger can do up to 96W)" means the Mac is drawing less than the charger offers, usually because the battery is nearly full.

Cable trust signals

WhatCable checks e-marker data against the USB Power Delivery spec. When something looks unusual, an orange card appears with the details. This is not proof that a cable is fake. It means something in the reported data is worth a closer look.

Checks include:

• Vendor ID compared against the USB-IF published list.
• Speed and current fields validated against PD spec ranges.
• Reserved bit patterns and zero-value metadata flagged.

Engineer mode

Hold Option and click the menu bar icon to show the underlying IOKit properties for each port. You can also enable this permanently from Settings.

Right-click menu

Right-click the menu bar icon for quick actions:

• Refresh to re-scan all ports.
• Keep window open to pin the popover (handy for screenshots and demos).
• Check for Updates to look for a newer version on GitHub.
• About and WhatCable on GitHub for links.
• Quit to close the app.

Settings

Click the gear icon in the popover header to open Settings.

• Hide empty ports: only show ports with something plugged in.
• Launch at login: start WhatCable automatically when you log in.
• Dock mode: run as a regular window instead of a menu bar icon.
• Notifications: get alerts when cables connect or disconnect.

Good to know

• E-marker data only appears for cables that carry one. Most cables under 60W are unmarked. Thunderbolt, USB4, and 100W+ cables will have one.
• Some cables only reveal their e-marker once a device is plugged in at the other end. If a cable shows up as basic, plug something into the far end and check again.
• WhatCable trusts the e-marker chip for cable capabilities. If a cable claims 240W / 40 Gbps but performs poorly, the chip is reporting incorrect data.
• Vendor name lookup uses USB-IF's published list. VIDs assigned after the bundled snapshot will show as "Unregistered / unknown" until the list is updated.