Spotify uses Replay Gain for normalizing every audio that uploads on its platform.
It helps to keep every audio at the same loudness level.
For example, every audio from 1924 to 1995 years has 60 db of Dynamic Range.
Now average audio has 12 db of Dynamic Range. It’s 4 x less dynamic range and 60x more distortion. So if you will listen to these two songs on the same speaker level – your ears will literally explode with new audio.
So Spotify normalizes both these files with a target of equivalent to -14 dB LUFS, according to the ITU 1770 standard.
So it basically levels the playing field between soft and loud masters. Louder tracks have often been cited as sounding better to listeners, so Loudness Normalization removes any unfair advantage.
So now you can stop heavily compressing your audio file to be louder.
However, it still may have some issues. Some of the Spotify users admit that some of the tracks are louder than others. It happens because Spotify uses its own algorithm (not ITU 1770 from the International Telecommunication Union)

So you will have problems if:
You have inaudible high-frequency content in your mix. Loudness algorithms (both ReplayGain and ITU 1770) do not have a lowpass cut-off filter, meaning any high-frequency content will add up to the energy measured by the algorithms and your track will be measured as louder by the algorithms than is actually perceived.
You have a really loud master (true peaks well above -2 dB) which makes the encoding add some distortion, adding to the overall energy of the track. That’s the energy as perceived by the algorithm, which might be inaudible to you but adds to the loudness from the algorithm’s perspective.
You’re not listening to a linear playback system. The ReplayGain algorithm (just like the ITU 1770 algorithm) can’t guess what audio playback system you’re using, so it can’t compensate for non-linearity in your system. Meaning, tracks that have more energy in the frequencies your system lifts up will sound much louder on your system.
A track that is very dynamic but mastered to -14 dB LUFS will have its peak levels preserved when played on Spotify. If you compare that to a loudly mastered track, at – 6 dB LUFS for example, its peaks get lowered to – 8 dB LUFS. The two tracks will playback at the same perceived loudness level, but the loud or “peak” parts of the more dynamic track will be much louder.
I know, it’s a lot of words and technical text. The main point is that a master track should be professionally mixed and mastered well, without super limiting and compression. It also works for any other streaming service (YouTube, Tidal, Google Music, Deezer).
You can find that a lot of award-nominated music these days has a nice dynamic range. We will help you to produce industry quality sounding songs properly for Spotify and any other music platform.