Add your OPUS file
Drop one or more .opus files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
OPUS to AAC
Re-encoding .opus audio as .aac changes how the sound is compressed and which players will accept it. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop OPUS files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting Opus audio to AAC audio
Re-encoding .opus audio as .aac changes how the sound is compressed and which players will accept it. An .opus file contains audio compressed with the Opus codec, stored in an Ogg container. Opus represents the current state of the art in lossy audio, beating MP3, AAC, and Vorbis in listening tests at nearly every bitrate from whisper-thin speech settings up to transparent music encoding.
An .aac file holds raw Advanced Audio Coding data, usually as an ADTS stream. AAC was designed as MP3's successor and delivers audibly better quality at the same bitrate, though the bare .aac extension is rarer than AAC audio traveling inside .m4a or .mp4 files. For this route the practical draw is noticeably more efficient than MP3 at equal bitrates and hardware decoding in essentially every phone and TV — balanced against raw ADTS files handle tags and cover art poorly, which is worth knowing before you commit a large batch.
Why convert OPUS to AAC?
The practical trigger for this conversion is usually a mismatch: with .opus, older car stereos, AV receivers, and MP3 players have never heard of it. Switching to .aac buys you noticeably more efficient than MP3 at equal bitrates, which is why it is the better fit for receiving the audio track copied out of MP4 video without re-encoding. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
OPUS vs AAC at a glance
| Aspect | Opus audio (.opus) | AAC audio (.aac) |
|---|---|---|
| Format type | Lossy — discards detail it judges invisible to shrink files | Lossy — discards detail it judges invisible to shrink files |
| How it stores data | the hybrid SILK/CELT design switches coding modes automatically based on content | a pure MDCT transform codec, free of the hybrid filterbank compromise that limited MP3 |
| Strongest at | compressing podcast and voice-chat audio to tiny files | receiving the audio track copied out of MP4 video without re-encoding |
| Weak spot | older car stereos, AV receivers, and MP3 players have never heard of it | raw ADTS files handle tags and cover art poorly |
| Metadata | vorbis comments in the OpusTags header, including cover art via METADATA_BLOCK_PICTURE, plus an output-gain field used for loudness normalization | no standard tag container exists for raw ADTS streams; ID3 tags are sometimes prepended but poorly supported, so wrapping in .m4a is the reliable way to tag AAC |
Pick AAC as the output
Select .aac in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if AAC is selectable, the route is real and validated.
Convert on your device
Press Convert. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid AAC file. Outputs keep the original filename with the .aac extension.
OPUS to AAC questions, answered
Will converting OPUS to AAC lose quality?
A second lossy step always costs a little, because opus is lossy-oriented and aac is lossy-oriented and each encoder discards detail differently (generation loss). At the default quality the difference is rarely visible; avoid repeated round-trips between .opus and .aac.
Is it private to convert OPUS files here?
Yes — the .opus file is processed inside your browser tab and never uploaded. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device. Close the tab and the file is gone from memory.
Where will the AAC file work?
AAC decoding is built into every browser, phone, and operating system, whether the audio arrives as a raw .aac stream or inside an .m4a wrapper. The last holdouts are elderly MP3-only car stereos and bargain portable players.
Will the AAC file be bigger or smaller than my OPUS?
It depends on the content: a pure MDCT transform codec, free of the hybrid filterbank compromise that limited MP3. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my OPUS file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, vorbis comments in the OpusTags header, including cover art via METADATA_BLOCK_PICTURE, plus an output-gain field used for loudness normalization; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert AAC back to OPUS?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .opus → .aac → .opus is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.