Will your song be turned down?

Loudness Units relative to Full Scale: loudness the way ears hear it, not just how high the wave goes. The sound is weighted the way hearing is (the deep bass counts for less, the upper middle a little more), then averaged over the whole song, leaving out the silent parts. Spotify, Apple Music, YouTube and Tidal all measure a song this way (ITU-R BS.1770) and then turn it up or down to their own level. One LU is one decibel of loudness.

So that one song is not louder than the next. A master at -8 LUFS is played about 6 dB quieter on Spotify, the same level as a master at -14. It gains nothing in loudness, and if the loudness came from squashing the peaks, it keeps the squashed sound and loses the punch. That is a trade to weigh, not a rule: plenty of club records are mastered loud on purpose.

Spotify turns a quiet master up, but only as far as its peaks allow: it keeps them 1 dB under full scale, so a quiet song with loud peaks stays quiet. YouTube never turns a song up at all. Some players, like Spotify's web player, do not change the level either way.

The wave between the samples can go higher than the samples themselves. True peak finds it by looking four times closer (4x oversampling), and dBTP is its level against full scale. The services stream encoded files (Ogg Vorbis, AAC, Opus), and encoding adds a little to the peaks, so a master that touches 0 can crackle once it is encoded. Spotify asks for -1 dBTP or lower, and -2 dBTP for a master louder than -14 LUFS.

A place where the wave sits flat at full scale for three samples or more in a row, in either channel, or goes over it (a 32-bit float WAV or an MP3 can). One sample touching full scale is counted in the peak, not as clipping.

How far the quiet parts sit under the loud ones, in LU (EBU Tech 3342): the loudness 3 seconds at a time, from the quietest tenth to the loudest twentieth, leaving out silence. A heavily compressed pop or EDM master can be under 4; an orchestra can be over 15.

It follows ITU-R BS.1770 for loudness and EBU Tech 3342 for the range, so on a WAV it should agree with a meter that does the same to within a few tenths. True peak is an estimate in every meter, this one included. An MP3 is measured as your browser decodes it, which can read a little differently from the WAV it came from. Before a release, your mastering engineer's meter is the one that counts.

As of October 27, 2026. Spotify publishes its level, -14 LUFS, and how it treats peaks. Apple Music, YouTube and Tidal publish no figure, so theirs are what engineers measure: about -16 for Apple Music's Sound Check and about -14 for the other two. Any of them can change, so every level on the reading can be edited, and the rows follow.

No. Your browser opens the file and measures it on this device. Nothing is sent to us or anyone else, and nothing is kept once you leave the page.