External hard drive are an essential piece of any computer setup. These high-capacity data storage devices are typically used for full-system (Time Machine) backups and to quickly share large digital media files. The most common external hard drives connects via USB 2.0/3.0, but there are other (faster) interfaces available including FireWire, Thunderbolt, USB-C, and others. Portable hard drives are powered by the USB connection, while external desktop hard drives must be plugged into a power outlet. Just like their internal counterparts, external hard drives can also fail so make sure you have multiple backups of important data.