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AU to M4A - Online Audio Converter
Convert AU to M4A online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
Convert AU to M4A
Drop AU audio here or click to select
AU
M4A (AAC)
About AU to M4A
Convert AU to M4A. AU is Sun's simple container, usually holding 8 kHz telephony audio. M4A is the MPEG-4 audio container usually holding AAC or ALAC. Check whether the track is AAC or ALAC before picking settings..
Why convert AU to M4A?
- Smaller files with M4A lossy compression.
- Keep quality where supported.
- Private, no upload - runs in your browser.
AU vs M4A
| Codec | PCM 16-bit | AAC |
|---|---|---|
| Compression | uncompressed | lossy |
| Sample behavior | Full quality kept | Quality set by bitrate |
| Typical use | AU is Sun's simple container, usually holding 8 kHz telephony audio. | M4A is the MPEG-4 audio container usually holding AAC or ALAC. |
When not to convert AU to M4A
- Skip M4A for archival masters: lossy compression discards detail, so keep the AU original.
- Keep a master copy: repeated exports stack small losses, so archive AU before batch M4A shares.
Limits
Starting point: AU - AU is Sun's simple container, usually holding 8 kHz telephony audio. Headers are minimal; verify sample rate after conversion. Check whether the track is AAC or ALAC before picking settings. Encode M4A (AAC) from AU at 256k for music or 128k for speech, starting from the master.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.
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FAQ
How do I convert AU to M4A?
Drop your AU file onto this page, choose quality and codec settings, then click Convert. The result downloads as M4A instantly. All processing runs in your browser.
What codec is used for M4A?
The default codec for M4A is AAC. You can change audio parameters in Advanced mode.
How do you store my files?
We do not store any processed audio. All conversion happens entirely in your browser using FFmpeg WASM.