Loudness normalisation explained: why mastering to -8 LUFS gets turned down on Spotify
Spotify plays music at -14 LUFS by default and turns louder masters down, so a -8 LUFS master buys you no extra volume, only less dynamic range and more risk of encoding distortion. Here is what Spotify, Apple and YouTube actually document, what they leave out, and how to make mastering decisions with that in mind.
Industryvia Spotify for Artists