1Upload the FLAC audio files whose level you want to change.
2Move the volume slider: above 100% makes the file louder, below 100% makes it quieter.
3Run it; the whole file is raised or lowered by the same amount, so a large boost can make loud passages clip.
4Download the adjusted FLAC file.
Adjust FLAC Volume FAQ
Can I adjust a whole batch to the same gain?
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Several files in one job need a paid plan. Free use is one file per conversion, one conversion an hour. On a paid plan you can add several files to one job, then download each result on its own or all of them in one ZIP.
How does Adjust FLAC Volume change the level?
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Concretely, the gain is applied to the PCM samples directly, so the change is exact and reversible; headroom is checked before writing so a boost clips nothing. You move the volume slider, where 100% leaves the level unchanged, and the change is applied evenly across the whole file.
Anything specific to FLAC to know?
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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. Relevant if you plan to adjust the level more than once.
Should I use volume or normalisation?
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Use volume when you know exactly how much louder or quieter you want it. Use normalisation when you want a set of files to end up at the same perceived loudness — that is a measurement problem, not a fixed gain, and applying one when you meant the other is the usual mistake.
What can I upload to Adjust FLAC Volume?
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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 Adjust FLAC Volume?
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Yes: free accounts process audio up to 15 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 Adjust FLAC Volume 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 Adjust FLAC Volume 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 Adjust FLAC Volume?
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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. Adjust FLAC Volume 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 Adjust FLAC Volume 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 Adjust FLAC Volume means the conversion is made from the version you settled on, not from the one you were still fixing.
Is Adjust FLAC Volume 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.
