M4A to Opus Converter
Convert M4A to Opus free — no upload, no signup
To convert M4A to Opus, drop your M4A 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. Shrink voice memos further with Opus.
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 M4A to Opus
Add your M4A files
Drag and drop M4A 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 M4A to Opus?
Opus keeps speech clear at very low bitrates, saving space for long recordings.
What happens when you convert M4A to Opus?
Fylo re-encodes to Opus at 48 kHz, 160 kbps by default; 64 kbps is plenty for voice.
How does Fylo convert M4A to Opus?
Fylo decodes the AAC (or ALAC) audio in the M4A 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 M4A you have. A 3-minute song is ≈ 3.6 MB at 160 kbps as M4A 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 M4A and Opus?
M4A is an MPEG-4 container that holds only audio — usually AAC, or Apple Lossless (ALAC). Apple popularised the extension with the iTunes Store in 2003; iPhone Voice Memos and many podcasts also use it. Audiobooks often use the related .m4b extension.
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: M4A format guide · Opus format guide
| Property | M4A | Opus |
|---|---|---|
| Compression | Lossy (AAC) or lossless (ALAC) | Lossy |
| Typical bitrate | 128–256 kbps | 24–160 kbps |
| 3-minute song | ≈ 3.6 MB at 160 kbps | ≈ 2.9 MB at 128 kbps |
| Tags and cover art | Yes (full, with cover art) | Yes (Vorbis comments) |
| Compatibility | Apple devices, Android, Windows 10+, browsers | Browsers, Android, WhatsApp, Discord; partial on Apple |
| Best for | iTunes/Apple Music libraries, voice memos, audiobooks | Voice notes, podcasts, streaming at low bitrates |
| Introduced | 2003 | 2012 |
Frequently asked questions
Good for lectures and meetings?
Yes — speech sounds clear even at 48–64 kbps.
Can I play Opus on Windows?
Yes, in VLC and modern browsers.
Is my M4A file uploaded to a server?
No. Fylo runs ffmpeg, the same engine used by professional video tools, compiled to WebAssembly inside your browser. Your M4A file is read directly from your device and never sent anywhere.
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