External hard drives are designed to work with most desktop and laptop computers and are available with widely used USB-A, USB-C, and Thunderbolt connections. The biggest consideration when choosing a connection type, is factoring for the connection speed. A faster connection will load images more quickly and apply edits much more smoothly than a slower connection.
USB-A, often referred to as simply USB, is the most common connection type for an external hard drive. Most portable external hard drives use USB 3.0 which allows for data transfer rates up to 5 Gbps.
USB-C is the newest USB format and has become standard on most recent computers. The port is smaller than USB-A and the plug is reversible so there is no risk of inserting the plug upside-down and bending pins or breaking the connector. USB-C can transmit data at speeds up to 20 Gbps.
Thunderbolt 3 ports and cables look virtually identical to USB-C but can transmit data at rates up to 40 Gbps.