AU to F4A 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 F4A audio exactly like M4A — to MP3, WAV or anything else.
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 F4A
| AU | F4A | |
|---|---|---|
| Compression | µ-law or PCM | Lossy AAC (ALAC for lossless) |
| Quality | Mono voice-grade (µ-law) | Strong at 128–256 kbps |
| Compatibility | Legacy Unix tools | Apple-first, modern platforms |
| Best for | Old system sounds and recordings | Music libraries and voice memos |
How to convert AU to F4A
- 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 F4A". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted F4A 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 F4A format
M4A is MPEG-4 audio: AAC (or ALAC) inside the MP4 container, minus the video. It became the iTunes Store's format in 2003 and never left — Apple Music downloads, voice memos and most phone recordings are M4A. At the same bitrate, AAC sounds distinctly better than MP3, which is why 128 kbps M4A competes with 192 kbps MP3.
Support is excellent across Apple devices, modern Android, Windows and every streaming SDK. The one historical caveat: iTunes Store music bought before 2009 carried FairPlay DRM; everything since (and everything you record yourself) is DRM-free.
+Strengths
- ✓Better quality than MP3 at the same bitrate
- ✓First-class on Apple and modern platforms
- ✓ALAC variant covers lossless needs
!Limitations
- −Very old feature phones and players miss it
- −Pre-2009 store purchases may carry DRM
Why convert AU to F4A?
Converting makes sense where the strengths of F4A meet what AU cannot give you. Better quality than MP3 at the same bitrate 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 F4A 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 F4A?
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.
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.
Will converting AU to F4A reduce audio quality?
If F4A is lossless, the output contains everything the AU file contains — no further loss is added. If F4A 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.