MP3 to AU Converter

Convert MP3 tracks to Sun/NeXT AU audio format

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Unix Audio Standard

AU is the native audio format for Sun/NeXT systems — convert your MP3 files for seamless integration with Unix workflows.

No Software Required

Run the MP3 to AU conversion directly in your web browser — no command-line tools or audio utilities needed.

Multi-File Processing

Convert a whole set of MP3 files to AU simultaneously — efficient for preparing audio assets for Unix-based systems.

How to convert MP3 to AU

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose au or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your au file right afterwards

About formats

MP3 (MPEG-1 Audio Layer III) is one of the most widely used digital audio encoding formats. It uses a form of lossy data compression to significantly reduce file sizes while retaining near-CD-quality sound, typically achieving a 10:1 compression ratio. Developed by the Fraunhofer Society in collaboration with other digital scientists, the format became an international standard in 1993 as part of the MPEG-1 specification. MP3 files can be encoded at various bit rates, commonly ranging from 128 kbps to 320 kbps, allowing users to balance file size and audio fidelity. The format's efficient compression, broad device compatibility, and small file sizes made it the driving force behind the digital music revolution, enabling practical music storage and distribution over the internet. Today, MP3 remains one of the most universally supported audio formats across virtually all media players, operating systems, and portable devices.
Developer: Fraunhofer Society
Initial release: December 6, 1991
AU is an audio file format introduced by Sun Microsystems for its Unix workstations and the NeXT platform. It features a minimal 24-byte header specifying data offset, size, encoding type, sample rate, and channel count, followed by the audio payload. AU supports numerous encodings, including uncompressed linear PCM at various bit depths, mu-law and A-law companding (logarithmic compression used in telephone systems), and several ADPCM variants. This versatility made AU a workhorse across early Unix environments, web audio (Java applets defaulted to AU), and telephony applications. One advantage is simplicity: the compact header and straightforward structure make it trivial to parse, generate, and stream programmatically. The built-in mu-law option provides another benefit, delivering reasonable voice quality at just 8 KB per second — half the rate of 16-bit uncompressed audio — invaluable when storage and bandwidth were scarce. Although modern formats have largely supplanted AU in consumer applications, it retains a foothold in scientific computing and audio processing pipelines where minimal overhead and reliable cross-platform behavior are valued.
Developer: Sun Microsystems
Initial release: 1992

Frequently Asked Questions

Why convert MP3 to AU?

AU is a standard audio format on Unix and Solaris systems. Java applications and some legacy Unix software expect audio data in AU format.

What opens AU files?

Audacity, VLC, SoX, and native audio tools on Unix/Linux systems handle AU files. Java multimedia APIs also support AU natively.

Is AU a lossy format?

AU can store both compressed (mu-law) and uncompressed (PCM) audio. The format is flexible, though most AU files use simple encoding.

Will the file size increase?

If the AU uses uncompressed PCM, yes — the file will be much larger than the compressed MP3 source. Mu-law encoding keeps sizes moderate.

Can I convert multiple MP3 files to AU?

Upload a batch of MP3 files and produce AU versions of each one in a single session — no need to convert one at a time.

MP3 to AU Quality Rating

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