A free Mac app called WhatCable has arrived to do something Apple should have built into macOS years ago: tell you what your USB-C cables actually do. Plug in any USB-C cable, and WhatCable displays its maximum data transfer speed, power delivery capacity, and e-marker information in plain English, no hardware required.
USB-C cables look identical but span a wild range of capabilities. Some support 40Gb/s data speeds, 8K video at 60Hz, and 240W power delivery. Others are power-only or max out at 480Mbps for data transfer. Every MacBook, iPad, and iPhone ships with a USB-C cable. Most people end up with a drawer full and no idea which one does what. Reach for a cable, plug it in, and hope it supports what you need. Connect an old iPhone cable to a new iPad and it won’t fast-charge. Connect a high-speed external SSD to the wrong cable and you get a bottleneck. Plug a slow charger into a MacBook Pro and it crawls on battery. These happen constantly, there is no way to know what you have without testing.
The app is straightforward. All you need to do is plug in a cable via USB-C, and WhatCable reads the embedded e-marker chip that every certified USB-C cable contains. It then displays:
- Maximum data transfer speed (480Mbps, 5Gbps, 10Gbps, 20Gbps, or 40Gbps)
- Power delivery rating (up to 240W)
- Video support (DisplayPort version, if applicable)
- USB version and feature set
- Manufacturer and certification details
WhatCable is free, available now, and requires nothing beyond an Apple Silicon Mac with a USB-C port. There’s one caveat though – not all Macs are built the same. Support for USB-C charging on M1 Pro and M1 Max MacBook Pros was just added recently as macOS does not expose the required information, so that app gets it directly from the battery controller now.
