1Upload every file you want combined — at least two of them.
2Add the files in the order you want them joined; the first file you add comes first.
3Start the merge; the files are joined one after another into a single file.
4Download the single combined Opus file.
Merge Opus FAQ
Does it matter if the inputs are different formats?
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It does. Opus is the best-in-class lossy codec at low bitrates and the standard for voice and real-time audio. Matching inputs take a fast, lossless path; mismatched ones have to be reconciled to a common format, which is slower and costs one encode.
Anything specific to Opus when merging?
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Yes — Opus always resamples to 48 kHz internally, so sample-rate choices you make elsewhere in the chain do not survive into it. That is worth checking when the inputs did not all come from the same source.
How does Merge Opus join the files together?
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Concretely, files that already share a codec, sample rate and channel layout are concatenated by copying the encoded frames, so the join costs nothing in quality; mismatched inputs are decoded and re-encoded once to a common format. Upload everything you want combined and the result comes back as a single file.
Can I run Merge Opus on several Opus audio files at once?
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Yes. Upload the set and they process in parallel with the same settings, which is the practical way to handle a podcast series or an album rather than repeating the job by hand.
Is there a file size limit on Merge Opus?
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Yes: free accounts process audio up to 15 MB per file, which at typical bitrates is several hours of material; ffmpeg does the decoding and encoding, exactly as it would on a desktop. That is the most generous cap on the site after video, and audio work rarely runs into it.
Why does a Word site host Merge Opus?
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WORD.to is built around the editable end of a document's life — the DOCX that is still being written, still being styled and still being argued over, before anyone flattens it for sending. Office files are containers full of other people's media — images, embedded audio, fonts — so the work people need on them is usually the work they would need on those contents anyway. Merge Opus shares the upload, the caps and the account with the conversions for that reason.
What should I do with the result once Merge Opus is finished?
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The converter on this site takes documents out to PDF for sending, to images for embedding and to plain text for anything that has to read them programmatically, and back the other way. Doing that afterwards keeps the editable original around, which is the part you cannot get back once it has been flattened.
Is Merge Opus here the same tool the sibling sites run?
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The engines are shared — the same document toolchain, the same workers, the same limits. What a Word site adds is a view on what survives leaving the Office format and what does not, which is the question every one of these jobs actually turns on. It also starts from one fact about the format this site is named after: the document is a zip of XML, so text edits are cheap and the weight is almost always the embedded images.
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.
