FLAC to AU Converter
FileFlip converts FLAC to AU 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 a FLAC file to AU?#
- Drop your FLAC 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 AU 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 AU file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting FLAC to AU lose quality?#
It depends on what is inside the file. FLAC is a container rather than a codec, so whether the AU 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 FLAC files online?#
Yes, because nothing is uploaded. FileFlip converts FLAC 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 FLAC to AU actually does to the file#
Converting FLAC to AU 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: FLAC → AU |
| 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 a FLAC file?#
A FLAC file holds audio compressed with the Free Lossless Audio Codec, which shrinks the data by roughly 40-60% and reconstructs the exact original samples, bit for bit, on decode.
Use FLAC to archive or edit audio when you want compression without giving up any of the source quality.
Convert FLAC to MP3 or AAC for a portable device or streaming use case where storage space matters more than keeping a bit-perfect copy.
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.
FLAC to AU questions people ask#
Does converting MP3 to FLAC improve the sound quality?
No, converting MP3 to FLAC does not improve sound quality. FLAC only guarantees that what goes into the encoder comes back out unchanged; it can't restore audio detail an MP3 encoder already discarded, so the result is a larger file that sounds exactly like the MP3 it came from.
What plays FLAC files?
VLC, foobar2000 and Audacity play FLAC on any platform, and it's natively supported by Windows Media Player since Windows 10, by the Music app on macOS since 10.13 High Sierra, and by Android's built-in player since Android 3.1. Apple's Music app on iOS has played FLAC since iOS 11.
Does FLAC support surround sound and high-resolution audio?
Yes, FLAC supports up to 8 channels, bit depths up to 32-bit and sample rates up to 1,048,575 Hz, well beyond what a CD or a standard streaming file needs. That headroom is one reason it's the format record labels and archives use for high-resolution reissues.
Is FLAC actually lossless?
Yes, FLAC is genuinely lossless: decoding a FLAC file reproduces the exact same digital samples that went into the encoder, bit for bit, unlike lossy formats such as MP3 or AAC that permanently discard data. The compression works by predicting each sample from the ones around it and storing only the much smaller difference.