Youtube-mp4 is a fast and safe Youtube video converter to mp4 file. Right now the converter is optimized for mp4 only. Make sure you aren't trying to download copyrighted materials.
You may also be interested in ...
Motion One
A new animation library, built on the Web Animations API for the smallest filesize and the fastest performance.
Shoelace
A collection of open source, professionally designed UI components built on a framework-agnostic technology.
Rallax
Rallax.js is a vanilla JS plugin that implements a dynamic parallax scrolling effect, without dependencies.