Every major streaming service measures the integrated loudness of your track (ITU-R BS.1770, in LUFS) and applies a playback gain so songs sit at a consistent level — the upload file itself is never modified. This tool measures your master with the same BS.1770-4 meter and computes, platform by platform, the gain that would be applied today: Spotify documents −14 dB LUFS in Normal mode (Loud −11 with a limiter engaging at −1 dB sample values, 5 ms attack / 100 ms decay; Quiet −19), and its boost rule leaves 1 dB of headroom for lossy encoding — a −20 LUFS master with −5 dBTP peaks is lifted only to −16, exactly as in Spotify’s published example. Apple Music’s Sound Check targets about −16 LUFS and turns quiet masters up; YouTube, Tidal and Amazon Music normalize loud masters down to about −14 LUFS but do not boost (Tidal normalizes by album; Amazon recommends −2 dBTP); Deezer targets −15 LUFS; SoundCloud’s player aims for −14 LUFS; Bandcamp plays your file as delivered; EBU R128’s −23 LUFS is included as the broadcast reference. The report shows, per platform: the target, the applied gain, the level your listeners will hear, the true peak after that gain, and whether the boost was capped by peak headroom. Two honest caveats from the platforms themselves: normalization is a listener-facing setting (Spotify, Apple and Tidal let users turn it off), and targets move over time — this is a preview of documented 2026 behavior, not a delivery spec. There is no loudness prize for exceeding a target: every dB gained above it is removed at playback, so master for the music and keep true peak at or below −1 dBTP (−2 dBTP for Amazon, and for masters louder than −14 LUFS on Spotify) so the lossy encoders have clean headroom.