Free online AAC to AU converter

AAC is a compressed audio format commonly used for music, streaming, and mobile devices. AU is an older audio container format originally used on Unix systems, often associated with simple, uncompressed or lightly compressed sound data. Converting AAC to AU is usually done for compatibility with legacy software, older systems, or specific audio workflows.

Why convert aac to au

You may need this conversion when an application only accepts AU files, when working with older Unix-based tools, or when preparing audio for systems that do not support modern compressed formats like AAC.

Best software for conversion

The most reliable option is FFmpeg, a powerful command-line converter that supports both AAC and AU. It is fast, free, and available on Windows, macOS, and Linux. For a simpler interface, Audacity can also open AAC files and export them as AU if the required codecs are available.

How to convert aac to au with ffmpeg

Use the following command:

ffmpeg -i input.aac output.au

This converts the AAC source into an AU file. If you need to control the audio codec or sample rate, FFmpeg lets you add extra parameters for better compatibility.

How to convert aac to au with audacity

Open the AAC file in Audacity, then choose File → Export → Export Audio and select AU as the output format if available. This is useful for users who prefer a graphical interface.

Important notes

• AU is less common than AAC and may not preserve modern metadata features.
• Because AAC is compressed, converting to AU does not improve audio quality.
• If the target system requires a specific sample rate or encoding, check its AU compatibility first.

Recommended choice

For most users, FFmpeg is the best converter because it is dependable, flexible, and supports batch conversion. If you want a visual workflow, Audacity is a good alternative.