The USB terminal on the back of the Nintendo Switch dock is supposed to support USB 3.0. It has been written on the official website from the beginning of the release. One of the members of the Nintendo switch forum asked ” Can I use an external hard disk? “
Answering the question, Nintendo officials confirm that External hard disk cannot be used with Nintendo Switch.
Furthermore, they also confirmed they would be working on it. “There is a plan to support this, but the model and the timing of the support are undecided. It will be announced on the Nintendo website as soon as it is decided” they added.