To delete videos in your YouTube "Watch Later" playlist, open the YouTube app or go to the website and log in. Navigate to the "Library" tab, then locate and open the "Watch Later" playlist. To remove all videos you've watched, click "Remove Watched Videos," which will clear the list of any videos you've completed. If you want to remove specific videos, click the three dots next to each video and select "Remove from Watch Later." While you can’t delete the entire "Watch Later" playlist, clearing it of unwanted videos will help keep your library organized.