Step 1: Supply your AAC files using the button above or by haul and lay.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Get your converted Opus files.
AAC to Opus Conversion FAQ
What does the AAC to OPUS audio converter do?
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It re-encodes a AAC audio file as OPUS. Sample rate and channel count are preserved; the difference is the codec and container.
Will the sample rate and channel layout be preserved?
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By default yes — stereo stays stereo, the original sample rate (44.1 kHz, 48 kHz, etc.) is carried through to the OPUS output.
Is the AAC to OPUS conversion reversible?
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You can convert the OPUS back to AAC on this site. If either format involved is lossy, the round-trip is not bit-perfect even though it is visually or audibly close.
What output quality should I expect from AAC to OPUS?
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Default settings target broadcast / web quality — visually identical to the source for most viewers. For archival use, pick the highest quality option in the converter settings.
Is converting AAC to OPUS a second round of lossy compression?
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Yes, and it is worth planning around. Both formats are lossy, so the OPUS encoder is working from audio that has already been through one psychoacoustic pass, and its own decisions compound the first set. At 192 kbps or above the result is still transparent for most listening. If you have a lossless master anywhere, encoding the OPUS from that instead avoids the double pass entirely. AAC is lossy but more efficient than MP3, and it handles up to 48 channels natively rather than being bolted onto a stereo design. Opus scales from 6 kbps mono speech to 510 kbps stereo music in the same bitstream and switches modes automatically.
What exactly is an OPUS file?
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A container with the audio inside it, rather than the audio on its own. That extra layer is where the length, the seek index and whatever metadata the format defines are kept, so a player knows how long an OPUS is before decoding a single frame instead of scanning the whole file to find out. It also means the extension does not always settle what is inside: several containers of this kind are allowed to hold more than one sort of audio, which is why two OPUS files can behave differently while looking identical from outside.
Why did my phone or tablet record in AAC?
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Because it is what the hardware encoder on the device produces. Voice memos, screen recordings and the audio track of anything filmed on a phone come out as AAC without anyone choosing it, which is why so many files arrive in it and why the quality is usually better than the file size suggests. Nothing about that stops it converting; it just means the source was encoded once already, by a chip optimised for battery life rather than for fidelity. AAC is Advanced Audio Coding, standardised in 1997 as MPEG-2 Part 7 and designed explicitly to replace MP3.
Will the OPUS play in my car or on older hardware?
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Often not. AAC is decoded by essentially everything, including car head units and elderly players; OPUS needs software that knows the codec, which standalone hardware frequently does not have. If the destination is a car stereo or a portable player, that is a strong argument for staying on AAC. Opus is almost never supported by standalone hardware — assume software playback only, and expect car stereos to ignore it.
Is there a licence attached to AAC?
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Not one you have to think about. The codec is covered by patent pools, and the licensing is settled by whoever ships the decoder — the phone, the browser, the operating system — long before a file reaches you. It is why the format is everywhere in hardware, and why royalty-free alternatives were built at all. It changes nothing about converting a file you already have, and it is only a live question if you are shipping an encoder yourself.
Is OPUS too new for the things I need to play it on?
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That is the one real risk with it. OPUS is a recent codec and it is genuinely better than the older ones at the same bitrate — noticeably so below 96 kbps — but "better" is not "supported", and a car head unit, a standalone player or a television from before it existed will simply not recognise the file. Browsers, phones and computers are fine. Check the oldest device that has to play it and choose on that, not on the numbers.
Is there a file-size limit when converting AAC to OPUS?
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Anonymous uploads are capped at a generous default; signed-in free accounts get a higher cap, and Pro accounts have no per-file limit. Browser memory is usually the practical constraint long before our server-side limits kick in.
Can I batch-convert several AAC files to OPUS at once?
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Yes. Drop or pick multiple AAC files in one upload — the converter processes them in parallel and returns a ZIP of the OPUS results. There is no need to repeat the upload step per file.
