Free online M4A to AU converter

M4A is an audio container format commonly used by Apple devices and software, usually storing AAC or ALAC audio. AU is a classic Sun/NeXT audio format often used in Unix-based systems and older audio tools. Converting M4A to AU is useful when you need compatibility with legacy software, embedded systems, or specific audio workflows that require AU files.

Why convert m4a to au

M4A files are widely supported on modern devices, but AU remains relevant in some technical and archival environments. You may want this conversion to:

• Use audio in older Unix or Sun-compatible applications
• Meet format requirements for specialized software
• Work with systems that prefer uncompressed or simple audio containers
• Preserve compatibility in legacy audio pipelines

Best software for conversion

The best all-around choice is FFmpeg, because it supports both formats, offers high-quality conversion, and works on Windows, macOS, and Linux. For a graphical option, Audacity is also a good choice if you prefer editing before exporting.

Recommended tools:

• FFmpeg — best for speed, batch conversion, and automation
• Audacity — best for manual editing and simple export
• VLC media player — useful for occasional conversions

How to convert m4a to au with ffmpeg

FFmpeg is the most reliable converter for this task. A basic command looks like this:

ffmpeg -i input.m4a output.au

If you need to control the audio codec or sample rate, you can specify them explicitly. For example:

ffmpeg -i input.m4a -ar 44100 -ac 2 output.au

This is helpful when the target application expects a particular sample rate or channel layout.

How to convert m4a to au with audacity

In Audacity, open the M4A file, make any edits if needed, then export it as AU. Use the menu path File → Export → Export Audio, then choose AU as the output format if available in your installation.

Audacity is a good option when you want to trim, normalize, or clean up the audio before saving it.

Things to keep in mind

• AU may not support every codec used inside M4A, so conversion usually re-encodes the audio.
• Quality depends on the source; if the M4A is already compressed, some quality loss may occur during re-encoding.
• Check compatibility with the target system, since AU variants can differ in supported encoding types.
• Batch conversion is easiest with FFmpeg or a dedicated converter.

Recommended workflow

1. Choose FFmpeg for fast and dependable conversion.
2. Use Audacity if you need to edit the audio first.
3. Verify the output AU file in the target application or player.

Summary

Converting M4A to AU is straightforward with the right tool. For most users, FFmpeg is the best converter because it is free, powerful, and highly compatible. If you need a visual interface and editing features, Audacity is the best alternative.