History will record videos that you watched on your computer. It will however record videos that you're unfamiliar with under the following circumstances.
- Your friends or family who share the computer with you has watched it.
- You accidentedly clicked on the video (*the video will be saved on ot the view history once it has been clicked.)
- The broadcaster decided to stream one of the videos from Niconico in one of the live broadcast you were watching
- You were using a pre-fetch tool or a prefetch function in Firefox extension.