AU
Sun Audio
An early audio format created by Sun Microsystems for Unix environments.
Commonly used for
Legacy Unix sound files
AU to AAC Converter
Convert AU files to AAC free in your browser — no signup, no install, and the file is never uploaded to a server. AAC 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 → AAC
What changes in this conversion
- AAC uses lossy compression, so some audio detail is discarded permanently in exchange for a much smaller file.
- AAC opens almost everywhere, so the converted file will work on devices and programs that refused the original AU.
How to use
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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.
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Confirm AAC as the output
AAC 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.
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Run the conversion
Press the convert button. Audio decodes and re-encodes in your browser — a normal song finishes in a few seconds.
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Download the AAC file
When it finishes, download the AAC file. Converting multiple files gives you the option to download them together as a ZIP.
About these formats
AAC
AAC Audio
A lossy format designed as MP3's successor, delivering better quality at the same file size. It is the default for iTunes, YouTube, and streaming services.
Commonly used for
Streaming audio, mobile music
Frequently asked questions
Is converting AU to AAC really free?
Yes. AU to AAC 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 AAC reduce quality?
AAC 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 AAC 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
Convert other formats to AAC
Audio converter
What each file format is, what it is used for, and which formats it can be converted to.
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