AU to CAF Converter
FileFlip converts AU to CAF entirely inside your browser, using FFmpeg compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert an AU file to CAF?#
- Drop your AU file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to CAF and the conversion starts on its own. FileFlip downloads 30.8 MB of WebAssembly the first time and nothing after that, then runs FFmpeg on your own machine.
- Save the CAF file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting AU to CAF lose quality?#
It depends on what is inside the file. AU is a container rather than a codec, so whether the CAF conversion copies the streams across untouched or re-encodes them is decided by the codecs that particular file happens to use.
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 AU to CAF actually does to the file#
Converting AU to CAF runs on FFmpeg, downloads 30.8 MB of WebAssembly the first time and nothing after that, re-encodes or copies through depending on the codecs in the file, and drops encoded streams.
| Engine | FFmpeg |
|---|---|
| Conversion path | One step: AU → CAF |
| Downloaded to your browser | 30.8 MB, once, then cached by your browser |
| Quality | Decided by the codecs inside the file |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Encoded streams | Dropped | The target format has nowhere to put it. |
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.
What is a CAF file?#
A CAF file holds audio in Apple's Core Audio Format, introduced in 2005 to replace AIFF and WAV on the Mac because its 64-bit chunk sizes have no practical file size or duration limit.
Keep audio as CAF while it stays inside Apple's own tools, such as Logic Pro, GarageBand, or an iOS app's own audio recordings, where the format's size and codec flexibility are used directly.
Convert CAF to WAV or M4A when the audio needs to leave the Apple ecosystem, since most non-Apple software has no built-in way to open it.
AU to CAF 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.
What creates a CAF file?
CAF files come from Apple's own audio software, including Logic Pro, GarageBand, and any iOS or macOS app that records audio through Apple's Core Audio APIs. Apple adopted CAF as its own format specifically to avoid the 4 GB size limit that WAV and AIFF both carry.