If you want to download a video from Youtube without any software then you can download it with the help of websites who provide platforms to download videos from Youtube as well as all other application or sites.
If you are looking for the free platform to download videos then you can download it from https://www.tubeninja.net/how-to-download/tumblr
. As I also use this website to download videos from Tumblr, Youtube, and many more because it provides free platform to download videos. You can also use this site to download videos from Youtube.