There are several video formats that can be found on the video sites. Most common formats are "flv" and "mp4". YTD will download videos in their original format. In case a downloaded video doesn't contain its extension within the file name (for example, is missing the ".mp4"), you will need to identify the correct type of the video file and rename it accordingly. For that open the video file in a text editor program such as Notepad and see if the first line of the file has "flv" or "mp4" in it.
If your computer doesn't recognize a certain format and is unable to play it we recommend you to use the following program: VLC Media Player is a free, open source program that can play almost any video type without requiring additional software. It also tells you what type of video a file is (load the video and select "Media Info" under the Tools menu).
