YouTube seems to abandoned their former loudness normalization algorithm and started to experiment with EBU R128 (LUFS) instead. Their new target value seems to be -14LUFS which is about 2 dB lower than before. They still leave material lower than their target unchanged which is both good and bad, good because everything ain’t supposed to be played back at the same level. Sad because that will make some aim for -14LUFS even if it doesn’t do the material any good, but hey, it’s better than -12!
This means a lot for us who are working with mastering, for one, they’re now at about the same target as Tidal, Spotify and Pandora which means the need for more than one master is even less relevant than before (we rarely deliver more than one master, but it happens). And, projects where YouTube will be the final destination, will be easier to mix and master as you will now have an additional 2dB of dynamics to work with.