AAC to Opus Converter
Convert AAC to Opus free — no upload, no signup
To convert AAC to Opus, drop your AAC audio files into the box below and click Convert. Fylo converts with ffmpeg running inside your browser, so nothing is uploaded and there's no signup or watermark. Opus makes AAC audio even smaller, especially speech.
Drop audio files here
or tap to browse · paste with Ctrl+V · add many at once
Your files never leave your device
Advanced
How to convert AAC to Opus
Add your AAC files
Drag and drop AAC files into the box or tap to choose them. The converter engine (about 31 MB) downloads once, the first time you convert.
Pick a bitrate
192 kbps suits music and 128 kbps or less suits speech. Sample rate and mono/stereo are under Advanced.
Convert and download
Click Convert, then download each Opus file or all of them as one ZIP.
Why convert AAC to Opus?
Voice apps and WebRTC tools use Opus for efficient streaming.
What happens when you convert AAC to Opus?
Fylo re-encodes to Opus at 48 kHz, 160 kbps by default.
How does Fylo convert AAC to Opus?
Fylo decodes the AAC audio in the AAC with ffmpeg compiled to WebAssembly and encodes it with FFmpeg's native Opus encoder at 160 kbps and 48 kHz in an Ogg container. Both formats are lossy, so each conversion discards a little detail — start from the highest-bitrate AAC you have. A 3-minute song is ≈ 3.6 MB at 160 kbps as AAC and ≈ 2.9 MB at 128 kbps as Opus. Opus always runs at 48 kHz, so the audio is resampled if needed.
What's the difference between AAC and Opus?
AAC (Advanced Audio Coding) was standardised in 1997 as part of MPEG-2 and later MPEG-4, designed to replace MP3. It achieves better quality at the same bitrate, especially below 128 kbps. A .aac file is usually a raw ADTS stream; the same audio inside an MP4 container is called M4A.
Opus is an open, royalty-free codec standardised by the IETF as RFC 6716 in 2012. It blends speech technology from Skype's SILK with music coding from Xiph's CELT, so it handles both voice and music well. Files are usually stored in the Ogg container with the .opus extension.
Learn more: AAC format guide · Opus format guide
| Property | AAC | Opus |
|---|---|---|
| Compression | Lossy | Lossy |
| Typical bitrate | 96–256 kbps | 24–160 kbps |
| 3-minute song | ≈ 3.6 MB at 160 kbps | ≈ 2.9 MB at 128 kbps |
| Tags and cover art | Limited in raw .aac (full in M4A) | Yes (Vorbis comments) |
| Compatibility | Very wide: Apple, Android, YouTube, browsers | Browsers, Android, WhatsApp, Discord; partial on Apple |
| Best for | Efficient music and video soundtracks | Voice notes, podcasts, streaming at low bitrates |
| Introduced | 1997 | 2012 |
Frequently asked questions
What bitrate for speech?
64–96 kbps.
Does Opus support stereo?
Yes.
Is my AAC file uploaded to a server?
No. Fylo runs ffmpeg, the same engine used by professional video tools, compiled to WebAssembly inside your browser. Your AAC file is read directly from your device and never sent anywhere.
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