Many sites does not let you to watch embed videos, until sharing them to social networks. But you can watch them, without sharing them.
Select the area around video with your mouse and some text around it. Then, right click on it and select “view source”.
In the selected code, you can find the “video-id”, where you can find the url from the video you are interested. Now copy the URL and go to the original site (eg “Youtube”) and watch the video.