AU to M4R 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. Converting MP3 to M4R is how you turn any song into a proper iPhone ringtone that syncs via Finder or iTunes.
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 M4R
| AU | M4R | |
|---|---|---|
| Compression | µ-law or PCM | Lossy AAC |
| Quality | Mono voice-grade (µ-law) | Same as M4A |
| Compatibility | Legacy Unix tools | iPhone only |
| Best for | Old system sounds and recordings | iPhone ringtones |
How to convert AU to M4R
- 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 M4R". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted M4R 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 M4R format
M4R is simply iPhone ringtone packaging: an AAC audio file (same as M4A) capped at 40 seconds, named .m4r so iOS treats it as a ringtone instead of a song. GarageBand and Finder sync are the supported paths to install one; the audio itself is ordinary AAC.
Practical workflow: pick the 30–40 second chorus you want, convert to M4R, sync it to the phone, and set it in Sounds & Haptics. Nothing about the audio changes — the extension and the length limit are the entire format.
+ Strengths
- ✓The native iPhone ringtone format
- ✓Simple — it is AAC with a new name
! Limitations
- −Hard 40-second length cap
- −Installation requires sync or GarageBand
Why convert AU to M4R?
Converting makes sense where the strengths of M4R meet what AU cannot give you. The native iPhone ringtone format 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 M4R 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 M4R?
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.
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.