You tube videos can be downloaded without copy pasting the video url to another site or installing chrome.It can be done using a simple click on the bookmarklet
A bookmarklet is an applet, a small computer application, stored as the URL of a bookmark in a web browser or as a hyperlink on a web page. Wikipedia
To do that you have to install the bookmarklet in your browser which is a very simple task.Drag and drop the following text into your browser’s bookmark area.
Get YouTube video (drag and drop this)
Now open the YouTube video which you wish to download and click the bookmark which you have created now.