1Upload every file you want combined — at least two of them.
2Drag the uploaded items into the order you want; the order is taken from the list, not from the filenames.
3Start the merge, which joins matching inputs without re-encoding them and reconciles mismatched ones exactly once.
4Download the single combined FLAC file.
Merge FLAC FAQ
Is the merge lossless?
+
It is whenever the inputs already agree — the encoded data is copied straight through. It stops being lossless only when the inputs disagree and something has to be re-encoded to make them compatible, and even then it is one pass, not one per file.
How does Merge FLAC join the files together?
+
Concretely, the PCM streams are joined sample-exactly, so the result is bit-identical to the inputs laid end to end — which is why lossless is the right family to assemble a master in. Upload everything you want combined and the result comes back as a single file.
Anything specific to FLAC when merging?
+
Yes — FLAC decodes bit-identically to the source, so any number of edit-and-resave cycles cost you nothing in fidelity. That is worth checking when the inputs did not all come from the same source.
How many files can I combine at once?
+
On the free tier a merge accepts two files at a time, which is deliberately higher than the single-file limit on other tools because merging one file is meaningless. A pass removes the cap entirely.
What can I upload to Merge FLAC?
+
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 Merge FLAC?
+
Yes: free accounts process audio up to 200 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 Merge FLAC lower the quality of my FLAC audio files?
+
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 Merge FLAC on several FLAC audio files at once?
+
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 Merge FLAC?
+
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. Merge FLAC 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 Merge FLAC is finished?
+
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 Merge FLAC means the conversion is made from the version you settled on, not from the one you were still fixing.
Is Merge FLAC here the same tool the sibling sites run?
+
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?
+
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.
