AU to AAC 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. AAC is the sweet spot when you want modern compression in an open, non-Apple container.
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 AAC
| AU | AAC | |
|---|---|---|
| Compression | µ-law or PCM | Lossy (LC/HE/xHE profiles) |
| Quality | Mono voice-grade (µ-law) | Best-in-class at low bitrates |
| Compatibility | Legacy Unix tools | Streaming/broadcast standard |
| Best for | Old system sounds and recordings | Streaming and mobile audio |
How to convert AU to AAC
- 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 AAC". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted AAC 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 AAC format
AAC (Advanced Audio Coding) is MP3's official successor, standardized in MPEG-2 and MPEG-4 and refined over two decades. It is the audio track of YouTube, iPhone voice memos, digital radio and HE-AAC streaming — arguably the most-played codec in history. Files appear either raw (.aac, ADTS stream) or inside M4A/MP4 containers.
Its claim to fame is low-bitrate performance: HE-AAC v1/v2 keep speech and music listenable at 24–64 kbps, where MP3 collapses. Raw .aac streams carry weaker tagging than the M4A container, which is why music libraries prefer M4A even when the codec is identical.
+ Strengths
- ✓The standard of streaming, mobile and broadcast
- ✓Excellent low-bitrate behavior (HE-AAC)
- ✓Better than MP3 at equal bitrate
! Limitations
- −Raw .aac files tag poorly
- −Flavor fragmentation (LC/HE/xHE) confuses tooling
Why convert AU to AAC?
Converting makes sense where the strengths of AAC meet what AU cannot give you. The standard of streaming, mobile and broadcast 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 AAC 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 AAC?
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 AAC reduce audio quality?
If AAC is lossless, the output contains everything the AU file contains — no further loss is added. If AAC 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.
Are tags like title and artist preserved?
Tag handling varies between target formats and this conversion focuses on the audio itself. For archival copies where tags matter, keep the original file; the converted copy is for playback and sharing.