Full screen YouTube still shows Dock and Menu Bar

If none of that works, open Terminal and enter killall Dock.

I have this same problem with YouTube, Netflix, mPlayerX and VLC, where the Dock stays visible (on-top) after making the video go full screen.

This problem can be fixed by going into System Preferences...Mission Control and turning off the option "Displays have separate spaces." You have to logout after making this change.

If you make the browser fullscreen before making the video fullscreen, this problem should disappear.

I had the same issue and I find it. This has to do with multiple monitors and mirroring (I connect my tv on the mac). Turn "Display mirroring" to off. That's it!

For me this works:

First switch Chrome window mode to full screen mode by pressing the green dot on the top left side of the view:

After that menu bar should be hidden so now enter full screen mode in youtube player:

Enjoy your video on full screen without menu bar.