1. From the YouTube home page, scroll down to the bottom of the page. You will find the ' History ' section.
2. After you click on History, YouTube will display a list of videos you have recently watched.
You can clear all watch history by checking the 'Watch History' box and clicking the 'DELETE ALL VIEW HISTORY' button.
If you just want to delete a few videos you've watched. You go to the video, click the X to the right of the video watched in the list
You notice right next to Viewing History is Search History and check it. A list of search history appears, click 'REMOVE ALL SEARCH HISTORY'
To delete individual items in your search history, click the X to the right of each of your search items
Generally all of the videos you see in History are videos you've watched, but if you see videos that you haven't watched, your account could be compromised. Your YouTube account is connected to your Gmail account and other accounts. So please consider the security issues offline!