To determine whether a device uses a USB-A or USB-C interface, one mainly observes the physical form and functional characteristics of the interface. The USB-A interface is rectangular, directional, and must be aligned correctly for insertion. It is commonly found in traditional computers, USB flash drives, and chargers, with a typical transmission speed of 5Gbps (USB 3.0 standard) and lower charging power (around 10W). It is widely used in modern mobile phones, tablets, and laptops, supporting data transfer speeds up to 40Gbps (USB4 standard), 100W fast charging, as well as video output (e.g., 4K display) and audio transmission. If the interface features a symmetrical design and supports fast charging or video expansion functions, it is USB-C; if it requires unidirectional insertion and has limited functionality, it is USB-A. It is advisable to select appropriate cables or adapters based on device requirements.
