For video search results, click the link Videos under the search box.
If video search results are particularly relevant for your search, they will appear automatically. (e.g. gangnam style)
If you add the word videos to your search, video search results will appear automatically no matter the search. (e.g. ocean videos)
To expand the video search results, click the grid icon at the top right of the video search results. To then collapse the results, click the X icon at the top right of the results.
You can also use !bangs to search for videos using other websites right from the DuckDuckGo search box. There are !bangs for GameTrailers (!gametrailers), the Food Network (!foodnetwork), and the History Channel (!history). For example, !foodnetwork pizza would search for pizza on the Food Network's website. The full list of !bangs are on the !bang page.
Prior versions on GitHub.