The best YouTube livestream chat extension there is. Very simple to use and has fantastic options to customize with.

Developer also updates as soon as YouTube does some tomfoolery which is greatly appreciated.

However a suggestion I may add is having the live chat be able to shift to the bottom of the video player when the browser window is cascaded to the side when there's two windows, similar to how FrankerFaceZ allows that option, because I tend to watch and do stuff on the side and also the YouTube stream does hard crash the browser tab when I cascade, requiring me to sometimes disable the extension in the video player.