When Dropbox Basic, Plus, or Business trial users share a video, the recipients can stream up to 15 minutes of it on dropbox.com. To view a longer video, recipients must download the file or watch it on a mobile app.
This limit only applies to recipients of a shared video. You can stream your own videos in their entirety on dropbox.com.
If a video is shared by a paid Business user, there is no streaming limit. Any recipient, regardless of their account type, can watch the full-length video.