I think you're missing the Chromecast button on the YouTube page. You shouldn't have to mirror the tab to fling YouTube to the TV.
Mostly I use it for Netflix, Google Play Movies & TV, and Plex.
Also if you have an Android or iPhone the native application on either device will have the Chromecast icon to fling the video. It's the same icon in Chrome (and maybe other browsers? I'm not sure) to fling from your computer.
Mostly I use it for Netflix, Google Play Movies & TV, and Plex.
Also if you have an Android or iPhone the native application on either device will have the Chromecast icon to fling the video. It's the same icon in Chrome (and maybe other browsers? I'm not sure) to fling from your computer.