# Free Mac app reveals true performance of your USB-C cables WhatCable instantly shows your cables' actual speed and power capabilities. - **Source:** [The Verge](https://www.theverge.com) - **Published:** 2026-07-13 - **Original article:** - **On Brifing:** https://brifing.si/s/949810f9-64f2-479f-8698-8ef294e2d1fe ## The Mystery of USB-C Cables While USB-C cables may look identical, their speed and power capabilities vary significantly. WhatCable app instantly reveals the true performance of these cables on Apple Silicon Macs. It displays critical information like supported data speeds, power capacity, and Thunderbolt compatibility. ## How It Works WhatCable accesses data that Macs collect about USB devices but don't normally show users. The port controller in Apple Silicon Macs retrieves power and data information from e-marker chips in connected cables. The app reads this data using Apple's public APIs and presents it through a user-friendly interface. ## Practical Use Cases Users can compare claimed specifications with actual performance of connected cables. For example, you can verify if a cable advertised as 100W charging actually delivers that power. Similarly, you can confirm the transfer speed of an SSD with a cable promising 10Gbps speeds. ## Unexpected Discoveries The app can reveal when cables fail to deliver their promised performance. Tests showed some cables claiming 10Gbps speeds actually operated at USB 2.0 speeds. It can also detect performance degradation in long-used cables that might need replacement. ## Advantages Over Other Solutions WhatCable provides more comprehensive information than physical cable testers. While $8 testers can verify basic cable specifications, they can't show real-time connection performance. WhatCable displays both cable specs and live performance metrics simultaneously. ## Why It Matters Choosing the right cable is crucial for high-speed data transfer and fast charging needs. WhatCable helps users avoid performance losses from incorrect cable choices. Being free and easy to use, it offers a practical solution accessible to all Mac users. ## Sources covering this story - https://www.theverge.com/gadgets/963759/whatcable-usb-c-cable-tester-app-mac — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._