U-04

LOUDNESS
READOUT
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Manual

  1. What LOUDNESS does

    LOUDNESS measures the integrated loudness (LUFS) and true peak of an audio file, so you can check it against a streaming platform's loudness target.

  2. How to use it

    Drop an audio file onto the drop zone, or click it to choose one. Press "Measure" and the whole file is analyzed; the result is shown as a meter and a numeric readout. Processing happens entirely in your browser; the file is never uploaded.

  3. What is LUFS

    Loudness Units Full Scale, a measure of perceived loudness based on the EBU R128 / ITU-R BS.1770 standard. Unlike a simple waveform peak (the highest sample value), it represents how loud the whole track feels. A value closer to 0 sounds louder; a more negative value sounds quieter.

  4. What is dBTP (True Peak)

    The peak level that can occur between digital samples once the audio is converted to analog, detected via oversampling. A sample-only peak meter can miss this kind of clipping. Exceeding 0dBTP can cause distortion on some playback devices.

  5. Typical platform loudness targets

    Most platforms automatically turn down anything louder than their target (loudness normalization), so staying close to the target helps your track play back at the level you intended.

    PlatformLoudness target
    YouTube-14 LUFS
    Spotify-14 LUFS
    Apple Music-16 LUFS
    Amazon Music-14 LUFS
    Broadcast (EBU R128)-23 LUFS

  6. Use case: checking loudness before you publish

    Before uploading to Spotify or YouTube, measure with LOUDNESS to see how far you are from -14 LUFS. If the gap is large, use the loudness normalize mode of the NORMALIZE tool to bring it to the target.

  7. Use case: comparing loudness across multiple tracks

    Before assembling an album or a playlist, measuring each track with LOUDNESS lets you spot perceived volume differences ahead of time. For tracks that stand out, consider evening them out with NORMALIZE.

  8. How it works: in-browser processing and privacy

    The whole file is analyzed, but everything happens entirely in your browser (a WebAssembly build of ffmpeg). The file is never sent to a server.

  9. Limits and troubleshooting

    Different services vary in analysis window and implementation details, so a small difference from a streaming service's own display — around ±0.5dB — is normal. Processing runs in your device's memory, so a very large file (roughly over 1GB) can fail to measure due to low memory.

  10. FAQ

    What’s the difference between LUFS and dB?
    dB (decibel) is a simple signal-level ratio, the kind a peak meter shows. LUFS adds perceptual frequency weighting and time integration on top of that, purpose-built for loudness.
    The measurement is slightly different from what a streaming service shows.
    Different services vary in analysis window and implementation details, so small differences are normal — a margin of about ±0.5dB is typical.
    Which file formats are supported?
    WAV, MP3, FLAC, AAC, M4A, OGG and most other common audio formats that ffmpeg can read.
    My measurement is off target — what do I do?
    Use the loudness normalize mode of the NORMALIZE tool to bring it to a target value such as -14, -16, or -23 LUFS.