Your video description box is one of the most important areas on YouTube and one of the most under utilized. Remember, Google indexes text and the description area is a perfect area that you can fill with text and weblinks. Description text is added while you are uploading your video.
There are several key areas to include in the Description box. The most important is the first sentence, which should have a full web address (including the http://), such as https://www.mapsfordesign.com, followed by a short intro description. The visible description area is very small. The first few words need to grab the viewer’s attention because this is all they will initially see below your video. A lot of people don’t even know that the description box has text in it and that they need to click the little arrow button to open it, but Google sees all and indexes this copy.