FreeTube - FreeTube is an open source desktop YouTube player built with privacy in mind.
YoutubeMultiDownloader - Just like its name YouTube Multi Downloader, it is an online website for downloading the videos of downloading without using any video download and accelerator.
NewPipe - NewPipe is a lightweight YouTube front-end for Android.
KeepVid - A free web application that allows you to download videos
YouTube Vanced - Vanced is a modded version of YouTube with many features such as adblocking and background playback
ShareTube - Watch YouTube, synced with friends.