AU Converter
FileFlip converts AU files into 11 other formats entirely inside your browser, using FFmpeg and WebCodecs compiled to WebAssembly. The AU file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. There is no file-size limit and no account to create.
How do I convert an AU file?#
- Drop your AU file onto the converter at the top of this page, or click it to pick one from your computer.
- Choose the format you want out of it. FileFlip downloads the engine that conversion needs, once, and your browser caches it.
- Conversion starts the moment you pick the format, and the result is yours to download. The work happens in this tab, so nothing is uploaded and nothing is queued.
Is it safe to convert AU files online?#
Yes, because nothing is uploaded. FileFlip converts AU files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What happens to a AU file#
FileFlip converts AU into 11 formats with FFmpeg and WebCodecs, all of it inside the browser tab. Each conversion below names the engine it uses, what it downloads, and exactly what that conversion keeps or drops.
| Category | Audio Files |
|---|---|
| File extension | .au |
| FileFlip support | Read and written |
| Conversions available | 11 |
| Engines | FFmpeg and WebCodecs |
| Downloaded to your browser | 30.8 MB on the first conversion, then cached |
What is an AU file?#
An AU file holds audio in Sun Microsystems' Unix workstation format, a plain header followed by raw sample data that was the standard system-alert and early web audio format before WAV and MP3 took over.
AU still shows up as the format Java's javax.sound and some Unix system tools default to for short sound effects, where its simplicity is the point.
Convert AU to WAV or MP3 when the audio needs to play in modern media players, browsers, or editing software that no longer ship AU support by default.
The AU file format reference covers the specification, the programs that open one, and what each conversion keeps or drops.
AU questions people ask#
What creates an AU file?
AU files come from Unix and Sun workstation software, from Java's built-in sound APIs, and from older system sound effects, since AU was the default audio format on SunOS and NeXT machines. Websites in the 1990s also used it for embedded sound clips before WAV and MP3 became standard.
What still opens AU files?
Audacity and VLC open AU files on any platform, and command-line tools like SoX handle them on Linux and macOS. Native support has otherwise faded from most operating systems and media players.
What should I convert an AU file to?
Convert AU to WAV to keep full quality for editing, or to MP3 for a smaller file that plays anywhere. Either target is more broadly supported than AU, which almost no current software treats as a default format.