Loudness meter. Check a song's LUFS and true peak, free, in your browser.

Questions

Is it free?

Yes, with no sign-up and no limit. The measurement runs on your computer.

Is my audio uploaded?

No. The file is decoded and measured inside your browser tab and never leaves your device.

What is LUFS?

Loudness Units relative to Full Scale: a measure of how loud audio sounds rather than how high its peaks go, defined by ITU-R BS.1770. Integrated LUFS is the figure for the whole song, with silence and very quiet passages gated out. One LU is one decibel.

Does my song have to be −14 LUFS for Spotify?

No. Spotify normalises playback: by default it turns tracks louder than −14 LUFS down to −14, and raises quieter ones only as far as their peaks allow, leaving 1 dB of headroom. A louder master isn't rejected, it is just played back at the same level as everything else, usually with less punch than a more dynamic master. Spotify publishes these numbers; the other services' figures here are measured by engineers rather than published, so treat them as approximate.

What's the difference between true peak and sample peak?

Sample peak is the highest stored sample. True peak estimates the highest point of the reconstructed waveform between samples, which can be higher. Lossy encoding (MP3, AAC, Ogg) can push those peaks higher still, which is why Spotify recommends keeping true peak below −1 dBTP, or −2 dBTP for masters louder than −14 LUFS.

Why might it differ slightly from my DAW's meter?

The browser decodes the file at 44.1 kHz, so a file at another sample rate is resampled before it is measured; integrated loudness barely moves, but sample and true peak can shift by a fraction of a dB. True peak here uses a 4× oversampling filter, accurate to about half a dB. A mono file is measured as it plays, on both speakers, which reads 3 dB above a strict single-channel measurement.

What formats work?

WAV, MP3, M4A/AAC, FLAC and OGG in most browsers. Safari does not decode OGG; use another format there.