AU to M4A Converter

Convert AU files to M4A free in your browser — no signup, no install, and the file is never uploaded to a server. M4A opens almost anywhere, so the result works where AU did not.

Completely free Files are never uploaded No signup required
Drop files or click to select
AU → M4A

What changes in this conversion

  • M4A opens almost everywhere, so the converted file will work on devices and programs that refused the original AU.

How to use

  1. Add your AU file

    Drag the AU file onto the drop area above, or click it to pick a file from your device. You can add several files at once.

  2. Confirm M4A as the output

    M4A is already selected as the output format on this page. You can pick the bitrate — higher keeps more of the sound, lower makes a smaller file.

  3. Run the conversion

    Press the convert button. Audio decodes and re-encodes in your browser — a normal song finishes in a few seconds.

  4. Download the M4A file

    When it finishes, download the M4A file. Converting multiple files gives you the option to download them together as a ZIP.

About these formats

AU Sun Audio

An early audio format created by Sun Microsystems for Unix environments.

Commonly used for Legacy Unix sound files

AU File format reference

M4A M4A Audio

An audio file in an MPEG-4 container, usually compressed with AAC. iPhone voice memos and iTunes purchases use this format.

Commonly used for iPhone voice memos, Apple ecosystem audio

M4A File format reference

Frequently asked questions

Is converting AU to M4A really free?

Yes. AU to M4A conversion is completely free with no signup, no watermark, and no daily limit on the free plan for ordinary use.

Are my AU files uploaded to a server?

No. The conversion runs entirely inside your browser using WebAssembly, so the AU file never leaves your device. That is also why it works without an internet connection once the page has loaded.

Does converting AU to M4A reduce quality?

M4A uses lossy compression, so some detail is discarded. At high quality settings the difference is usually invisible, and the file becomes far smaller.

Is there a file size limit for AU to M4A conversion?

The free plan handles files up to 200MB. Because processing happens on your own device, very large files depend on your computer's memory rather than a server quota.

Convert AU files to other formats

AU AAC AU FLAC AU MP3 AU OGG AU OPUS AU WAV

Convert other formats to M4A

3G2 M4A 3GP M4A AAC M4A AC3 M4A AIF M4A AIFF M4A ALAC M4A AMR M4A ASF M4A AVI M4A DIVX M4A DTS M4A

Audio converter

What each file format is, what it is used for, and which formats it can be converted to.

Open converter Browse the full format reference