AU to MP3 Converter
Processing entirely on your device — large files may take a moment.
AU is the µ-law audio format of old Unix systems and Java applets — tiny mono files from another era. Convert audio to MP3 for maximum compatibility at a small file size.
iLoveConverter processes everything locally on your computer, which makes it private and fast: no upload wait, no server storage, no limits. Add as many files as you like — batch conversion is built in.
How AU compares to MP3
| AU | MP3 | |
|---|---|---|
| Compression | µ-law or PCM | Lossy (psychoacoustic) |
| Quality | Mono voice-grade (µ-law) | Good, capped at 320 kbps |
| Compatibility | Legacy Unix tools | Plays everywhere |
| Best for | Old system sounds and recordings | Music sharing and compatibility |
How to convert AU to MP3
- 1
Select your files
Drag & drop your AU files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to MP3". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted MP3 file individually, or grab everything at once as a ZIP archive.
About the AU format
AU is Sun Microsystems' audio format from the Unix workstation age: a small header followed by µ-law (or PCM) samples. Java's applet era shipped it everywhere, and old Unix sound tooling still emits it.
Modern players increasingly skip it. Converting AU to WAV preserves the samples bit-for-bit while moving the file into universal territory — the standard rescue path for system sounds and old recordings.
+ Strengths
- ✓Simple, lossless sample storage
- ✓Native to old Unix/Java tooling
! Limitations
- −µ-law flavor sounds dated and mono
- −Dropped by modern players
About the MP3 format
MP3 (MPEG-1 Audio Layer III) defined digital music: standardized in 1993, popularized by Napster and the first portable players, and freed of all patents in 2017. It is lossy psychoacoustic compression — it discards frequencies the ear supposedly won't miss — at bitrates from 128 to 320 kbps, with ID3 tags carrying title, artist and cover art.
Twenty years of competitors have failed to displace it, because playback support is absolute: every device that has ever played music plays MP3. At 320 kbps even critical listeners struggle to identify it in blind tests, though modern codecs reach the same quality at noticeably lower bitrates.
+ Strengths
- ✓Plays on absolutely everything
- ✓Rich tag ecosystem (ID3, cover art)
- ✓320 kbps is transparent for most listeners
! Limitations
- −Lossy ceiling — never a mastering format
- −Less efficient than AAC/Opus at equal quality
- −Low-bitrate artifacts are audible and permanent
Why convert AU to MP3?
Converting makes sense where the strengths of MP3 meet what AU cannot give you. Plays on absolutely everything Meanwhile µ-law flavor sounds dated and mono One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this AU to MP3 converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for AU to MP3?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Will converting AU to MP3 reduce audio quality?
If MP3 is lossless, the output contains everything the AU file contains — no further loss is added. If MP3 is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.
Can I convert a whole folder of AU files?
You can select many files at once and they are processed in a single batch. Output files land in one ZIP download when there is more than one result.