A free app for Android, by New Pipe.

Pure Tube: Ads Block for Video is the perfect app for anyone who wants to surf the internet on their smartphone or tablet without being bothered by ads and other unwanted content. This is one of the best ad blocker apps for Android devices and it works really well. This application blocks all advertisements displayed on the site. Also, all recommendations and comments are hidden. That way you can’t see them and click on them. This is a lightweight app that you can download to your phone or tablet. It even has Floating Popup Play Mode for easy viewing. You can even stream music in quick succession.