1Upload the audio files you want brought to a consistent loudness.
2There is nothing to set: the loudness is brought to -16 LUFS (EBU R128), with true peaks kept below -1.5 dBTP.
3Run the analysis; integrated loudness and true peak are measured before any gain is decided on.
4Download the normalized Audio file.
Normalize Audio Loudness FAQ
How does Normalize Audio Loudness decide the right level?
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Concretely, the file is analysed for integrated loudness and true peak, then a single gain is applied to reach the target — no compression, no limiting, just the level. The file is measured first and the correction follows from the measurement, rather than a fixed gain being applied and hoped for.
Anything specific to Audio here?
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Yes — the codec is detected from the stream, so a mislabelled extension does not derail the job. Worth knowing when the goal is a consistent set rather than one file.
Which audio formats does Normalize Audio Loudness accept?
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MP3, WAV, AAC, M4A, FLAC, OGG, Opus, WMA and AIFF. Codecs are detected from the stream rather than the extension, so a mislabelled file still works and a mixed batch is handled per file.
Is there a file size limit on Normalize Audio Loudness?
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Yes: free accounts process audio up to 15 MB per file whichever codec you brought; ffmpeg handles the decode and encode. In practice that limit only bites on uncompressed WAV; a compressed file of the same length is nowhere near it.
Can I run Normalize Audio Loudness on several audio files at once?
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Yes. The set queues in parallel with identical settings, which is how you process an album or a podcast back catalogue without repeating yourself.
Why does a EPUB site host Normalize Audio Loudness?
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EPUB.to is built around the open eBook format — XHTML in a zip, reflowable by design, and readable on hardware nobody has thought about the layout for. A book is a zip full of markup, images and fonts, so almost every job people bring to an eBook site is really a job on one of those things. Normalize Audio Loudness runs on the same upload and the same account as the conversions because that is where it is needed.
What should I do with the result once Normalize Audio Loudness is finished?
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The converter on this site moves books between EPUB, MOBI, AZW3, PDF and DOCX, so a title ends up on whatever hardware is actually going to read it. Doing that after Normalize Audio Loudness means the conversion is made from the version you settled on, not from the one you were still fixing.
Is Normalize Audio Loudness here the same tool the sibling sites run?
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The engines are shared — the same toolchain, the same workers, the same limits. What a EPUB site adds is a view on reflow: which of these operations a reflowable book genuinely supports, and which ones only make sense on the fixed-layout media inside it. It also starts from one fact about the format this site is named after: the book is a zip of XHTML with a manifest, so the text costs almost nothing and every decision that matters is about the embedded images and font subsets.
Do I need an account, and does anything get kept?
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No account is needed. Uploads and results are kept for about 24 hours, which leaves time to download the result, and are then deleted automatically; nobody reads, lists or indexes them. Several files in one job need a paid plan.
