AU Compressor
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Supports: AU
Advanced Options - Our defaults are optimized for the best results. We recommend you keeping the defaults unless you have a specific need.
Reset to defaults
Need help?How to Compress AU Audio Online
- Upload Your AU Files: Click "+ Add Files" to select AU audio files from your computer, Google Drive, or Dropbox.
- Choose Settings: Select audio codec, compression method (quality preset, target file size, or bitrate), sample rate, and channel configuration (stereo/mono). Optionally trim with start time and duration.
- Download Compressed Files: Click "Compress" and download your smaller AU files.
What Is AU Format?
AU (Audio) is a simple audio file format created by Sun Microsystems (now Oracle). It was the standard audio format on Unix and NeXT systems in the 1980s-90s.
AU files are typically found in:
- Legacy Unix/Solaris systems
- Java audio applications (
javax.sound) - NeXT/OpenStep software
- Older telephony and voicemail systems
- Scientific computing environments
AU vs Modern Audio Formats
| Feature | AU | WAV | MP3 |
|---|---|---|---|
| Developer | Sun Microsystems (1980s) | Microsoft/IBM (1991) | Fraunhofer (1993) |
| Compression | μ-law, A-law, or PCM | Usually uncompressed | Lossy |
| File size | Medium (μ-law) to large (PCM) | Large (uncompressed) | Small |
| Modern support | ⚠️ Limited | ✅ Universal | ✅ Universal |
| Use case | Legacy Unix, Java | Professional editing | Sharing, streaming |
Competitors like happyscribe.com compress audio files "right from your browser" supporting MP3, WAV, FLAC, M4A, OGG. todaycalculator.com offers bitrate selection from 64kbps to 320kbps. ez2conv.com reports "up to 90% reduction with Minimum Size preset" and notes "mono audio instead of stereo halves the file size." Few competitors specifically target AU — XConvert is one of the few with a dedicated AU compression page.
Frequently Asked Questions
Is it free?
Yes. Completely free with no sign-up required and no file count limits.
Should I compress AU or convert to MP3/WAV?
If your system requires AU format, compress within AU. Otherwise, converting to MP3 (for sharing) or WAV (for editing) gives you better compatibility with modern software.
Can I change the sample rate?
Yes. Adjust sample rate in the settings. Common rates: 8kHz (telephony), 22.05kHz (voice), 44.1kHz (CD quality), 48kHz (video standard).
Can I compress multiple files at once?
Yes. Upload multiple AU files and compress them all with the same settings.
Does it work on mobile?
Yes. Works in any modern browser on all devices — no app installation required.