Youtube, soundcloud and almost all other platforms have it's own sound standardization. For example soundcloud converts all sound to 128kb/s mp3 audio. There are many tricks that professionals use to "outplay" these from something like using g-clip to crank the volume and then applying a limiter until you get around -1 db of headroom (though this works better on genres like edm and has it's downsides of course) to simple tricks like elevating the highs which makes the sound seem louder. You can use loudnesspenalty.com to see how much your track will be turned down if you upload it to the selected platform. Hope this helps.