AU to MP3 Converter
Initializing... drag & drop files here
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 Convert AU to MP3 Online
- Upload Your AU File — Click "Choose Files" or drag and drop your .au audio file. Batch conversion is supported.
- Adjust Settings (Optional) — Set the MP3 bitrate (128 kbps for small files, 192–320 kbps for high quality) or adjust the sample rate.
- Convert and Download — Click "Convert" and download your MP3 file. No watermark, no sign-up required.
Why Convert AU to MP3?
AU (Audio) is a simple audio format developed by Sun Microsystems for Unix and NeXT systems. It typically stores audio using μ-law (mu-law) encoding at 8 kHz sample rate — essentially telephone-quality audio. While AU was once common in early web audio and Unix sound systems, it's now a legacy format with very limited support outside of Audacity and VLC.
MP3 is the universal audio standard supported by every device, player, and platform. Converting AU to MP3 makes your audio files playable everywhere while dramatically reducing file size through efficient MPEG Layer 3 compression.
Common use cases include converting legacy Unix sound files for modern playback, updating old web audio assets, or making Audacity project exports compatible with standard music players.
AU vs MP3 Comparison
| Feature | AU (Sun Audio) | MP3 |
|---|---|---|
| Encoding | μ-law / PCM | MPEG Layer 3 |
| Typical sample rate | 8 kHz (telephone quality) | 44.1 kHz (CD quality) |
| Device support | ❌ Unix/Audacity only | ✅ Universal |
| File size (1 min) | 480 KB (8-bit μ-law) | 1–2.5 MB (128–320 kbps) |
| Web browser support | ❌ No | ✅ All browsers |
| Quality | Low (8-bit) | Good to excellent |
Frequently Asked Questions
Will converting AU to MP3 improve audio quality?
No — conversion can't add quality that isn't in the source. If your AU file is 8 kHz μ-law (telephone quality), the MP3 will sound the same. However, if your AU file contains higher-quality PCM audio, converting to MP3 at 192+ kbps will preserve that quality in a much smaller file.
What bitrate should I use for AU to MP3?
For AU files with standard 8 kHz μ-law encoding, 128 kbps is more than sufficient since the source quality is limited. For AU files with higher-quality PCM audio, use 192–320 kbps.
Can I batch convert multiple AU files?
Yes. Upload multiple AU files and they will all be converted to MP3 with the same settings. Download individually or as a ZIP archive.
What programs create AU files?
AU files are primarily created by Audacity (as an export option), legacy Unix/Solaris systems, and some older Java audio applications. The format was also used for early web audio via the <embed> tag before MP3 and HTML5 audio became standard.