Free online M4R to AU converter

M4R is an audio file format used mainly for iPhone ringtones. It is based on the AAC codec and is commonly just a renamed .m4a file with a ringtone-friendly purpose. AU is a classic audio format developed by Sun Microsystems, often used in Unix-based systems and supported by many audio tools. Converting M4R to AU changes a modern compressed ringtone file into a more traditional audio container that may be useful for compatibility, editing, or archival workflows.

Why convert m4r to au

You may want to convert M4R to AU if you need broader support in older audio software, Unix environments, or specialized tools that work better with AU files. Since M4R is tied to Apple ringtone usage, converting it can make the audio easier to reuse outside the iPhone ecosystem.

Best software for conversion

The best all-around choice is FFmpeg, because it is fast, free, and supports both formats reliably. It works on Windows, macOS, and Linux, and it can convert audio without needing a graphical interface. If you prefer a simple desktop app, Audacity is also a good option for opening M4R and exporting to AU.

How to convert with ffmpeg

Use this command:

ffmpeg -i input.m4r output.au

This will read the M4R file and create an AU file. If the source audio is protected or encoded in a way that your tool cannot read directly, first rename the file to .m4a and try again, since many M4R files are AAC audio in an M4A-style container.

How to convert with audacity

Open the M4R file in Audacity, then choose File → Export → Export Audio and select Sun/NeXT AU as the output format. This method is useful if you want to trim, normalize, or edit the ringtone before saving it as AU.

Things to keep in mind

• Quality: AU conversion usually preserves the existing audio quality, but the result depends on the export settings.
• Compatibility: AU is widely recognized in Unix and legacy audio environments, but not as common in modern consumer devices.
• Metadata: Ringtone-specific tags from M4R may not carry over to AU.
• Duration: M4R files are often short ringtone clips, so the converted AU file will usually be short as well.

Recommended workflow

1. Check whether the M4R file plays normally in your audio player.
2. Use FFmpeg for the quickest conversion.
3. Use Audacity if you need editing before export.
4. Verify the AU file in your target application.

Best choice overall: FFmpeg for speed and reliability, or Audacity if you need manual editing.