A new macOS menu bar app called WhatCable solves one of the most frustrating problems with USB-C: figuring out what a cable can actually do. The app reads data your Mac already has access to via IOKit and displays it in plain English—charging wattage, data speeds, Thunderbolt support, and whether your cable is bottlenecking your setup.

The app shows per-port diagnostics including cable speed (USB 2.0 through 80 Gbps), current rating (3A or 5A, translating to 60W-240W), and even the e-marker chip vendor. When charging is slow, WhatCable identifies the culprit: whether the cable, charger, or Mac itself is limiting power delivery. It also displays the full PDO list from chargers and identifies connected devices.

Built by Darryl Morley in Swift/SwiftUI, WhatCable is open source, free, and requires macOS 14 or later. The app is universal (Apple silicon + Intel), signed with a Developer ID, and notarized—no Gatekeeper warnings. It reads three families of IOKit services with no entitlements or private APIs. For anyone who's ever dug through a drawer full of identical-looking USB-C cables wondering which one supports fast charging or external displays, this tool finally provides answers without the guesswork.