It depends on how you access the video. For purchased videos, you can feel free to stream them, but download them on up to 4 devices. Those who rent videos from Amazon Prime and Prime Video Mobile users can only download videos on 1 device, and the latter is only allowed to stream Amazon Prime videos on 1 device as well. If you are Prime Subscription users, Amazon Prime Video allows you to stream content on up to 3 devices simultaneously with a single account. However, there's a catch: you cannot watch the same title on more than 2 devices at the same time.