If you are not sure if you have viewed a video on YouTube earlier, then you you can use one of their features which puts a tag once you view a video. This is helpful if you are searching for a particular video and there are a lot of videos with same or similar tags. When you watch a video, a small tag "previously viewed" gets added next to the video as shown in the image below … [Read more...] about How Will I Know If I Have Previously Viewed A Video On YouTube ?