AAC to AU Converter
Processing entirely on your device — large files may take a moment.
AAC Audio and Sun Microsystems Audio exist for different jobs: AAC (Advanced Audio Coding) is the successor to MP3 — about 30% better quality at equal bitrates, used by YouTube, iPhone and most streamers. Converting AU to WAV preserves the samples in a format every modern tool reads.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How AAC compares to AU
| AAC | AU | |
|---|---|---|
| Compression | Lossy (LC/HE/xHE profiles) | µ-law or PCM |
| Quality | Best-in-class at low bitrates | Mono voice-grade (µ-law) |
| Compatibility | Streaming/broadcast standard | Legacy Unix tools |
| Best for | Streaming and mobile audio | Old system sounds and recordings |
How to convert AAC to AU
- 1
Select your files
Drag & drop your AAC 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 AU". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted AU file individually, or grab everything at once as a ZIP archive.
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
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
Why convert AAC to AU?
Converting makes sense where the strengths of AU meet what AAC cannot give you. Simple, lossless sample storage Meanwhile Raw .aac files tag poorly One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this AAC to AU 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 AAC to AU?
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 AAC to AU reduce audio quality?
If AU is lossless, the output contains everything the AAC file contains — no further loss is added. If AU 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.