1Upload the FLAC audio files you want brought to a consistent level — a whole set at once is exactly the case this is for.
2Pick a target: about -14 LUFS for streaming platforms, -16 LUFS for podcasts, -23 LUFS for broadcast.
3Run the analysis; integrated loudness and true peak are measured before any gain is decided on.
4Download the normalized FLAC file, with the dynamics inside each track left untouched.
Normalize FLAC Loudness FAQ
Does normalisation compress the dynamics?
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No. It is a single gain adjustment for the whole file, so the relationship between the quiet and loud parts is untouched. Compression and limiting are separate operations and are not applied here.
How does Normalize FLAC Loudness decide the right level?
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Concretely, R128 loudness analysis drives an exact gain applied to the PCM, so a whole album can be brought to one target level with the relative dynamics inside each track untouched. 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 FLAC here?
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Yes — FLAC decodes bit-identically to the source, so any number of edit-and-resave cycles cost you nothing in fidelity. Worth knowing when the goal is a consistent set rather than one file.
What loudness target should I aim for?
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About -14 LUFS is what the major streaming platforms normalise to, -16 LUFS is the usual podcast target, and -23 LUFS is the broadcast standard. Going louder than the platform target gains you nothing — the platform simply turns it back down.
What can I upload to Normalize FLAC Loudness?
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WAV, FLAC and AIFF, at any bit depth and sample rate up to and including 24-bit/192 kHz. Lossy files work in the same batch if you are mixing sources.
Is there a file size limit on Normalize FLAC Loudness?
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Yes: free accounts process audio up to 25 MB per file — for uncompressed PCM that is roughly twenty minutes of CD-quality stereo, so it is a real limit here in a way it is not for MP3. If you are over it, converting WAV to FLAC first is the free fix — it is lossless and roughly halves the size.
Will Normalize FLAC Loudness lower the quality of my FLAC audio files?
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No. Lossless audio is edited sample-exactly, so what comes back decodes bit-identically to what you would get doing the same edit in a desktop editor. You can repeat the cycle as many times as you like without accumulating any loss at all.
Can I run Normalize FLAC Loudness on several FLAC audio files at once?
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Yes, though lossless files are large, so the batch is bound by upload bandwidth rather than by processing. Settings apply uniformly across the set.
Why does a EPUB site host Normalize FLAC 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 FLAC 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 FLAC 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 FLAC Loudness means the conversion is made from the version you settled on, not from the one you were still fixing.
Is Normalize FLAC 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, and nothing is kept: uploads are deleted from the workers shortly after the job finishes, nothing is read and nothing is indexed. Free accounts exist for history and batch size, not for access.
