M4R to AU Converter
Processing entirely on your device — large files may take a moment.
iPhone Ringtone and Sun Microsystems Audio exist for different jobs: M4R is Apple’s ringtone format — technically an AAC file capped at 40 seconds that iTunes and iPhones recognise as a ringtone. 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 M4R compares to AU
| M4R | AU | |
|---|---|---|
| Compression | Lossy AAC | µ-law or PCM |
| Quality | Same as M4A | Mono voice-grade (µ-law) |
| Compatibility | iPhone only | Legacy Unix tools |
| Best for | iPhone ringtones | Old system sounds and recordings |
How to convert M4R to AU
- 1
Select your files
Drag & drop your M4R 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 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
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 M4R to AU?
There is a concrete reason this conversion exists: Hard 40-second length cap AU sidesteps that — Simple, lossless sample storage If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this M4R 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 M4R 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.
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 M4R to AU reduce audio quality?
If AU is lossless, the output contains everything the M4R 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.