Just added this extension today to Firefox on Mac running on High Sierra, turned on a Youtube playlist I created which was filled with ads at the start of every video, and not one ad appears now, it's almost too good to be true

Work very well to remove youtube ads

Works really well. YouTube was full of ads and unwatchable before this extension. Now I can watch ads free with this extension. I can't support directly by financial means, but I am sharing this extension to others.

best for ever

I haven't seen an advert for months! I can't say much else about this as it just works in the background.

What happens? well it won't make ads disappear, but you won't have to watch/hear them - the video goes a grey color and youtube throws an error while their ad isn't being shown to you. It even skips the ad after 5 seconds for you, your video plays automatically or you press play again.