Add your FLAC file
Drop one or more .flac files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
FLAC to AU
Re-encoding .flac audio as .au changes how the sound is compressed and which players will accept it. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop FLAC files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting FLAC audio to Sun audio
Re-encoding .flac audio as .au changes how the sound is compressed and which players will accept it. A .flac file contains audio compressed with the Free Lossless Audio Codec, which shrinks recordings without discarding a single sample. Decoded .flac output is bit-identical to the source, so the format has become the standard for music archiving and high-resolution downloads.
An .au file is the Sun audio format, one of the earliest structured audio files, created for Unix workstations. A minimal header followed by sample data, classically 8 kHz mu-law telephony audio, makes .au about as simple as an audio format can get. For this route the practical draw is so simple that nearly any audio tool can parse it and pCM variants preserve the recording exactly — balanced against essentially obsolete outside legacy systems, which is worth knowing before you commit a large batch.
Why convert FLAC to AU?
The practical trigger for this conversion is usually a mismatch: with .flac, still several times larger than a good lossy encode. Switching to .au buys you so simple that nearly any audio tool can parse it, which is why it is the better fit for maintaining sound assets in vintage Unix and Java software. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
FLAC vs AU at a glance
| Aspect | FLAC audio (.flac) | Sun audio (.au) |
|---|---|---|
| Format type | Lossless — every pixel or sample is preserved exactly | Lossless — every pixel or sample is preserved exactly |
| How it stores data | linear prediction followed by Rice coding typically yields files 40 to 60 percent the size of raw PCM | a 24-byte header carries a '.snd' magic number, data offset, encoding type, sample rate, and channel count |
| Strongest at | ripping CD collections for permanent archival | maintaining sound assets in vintage Unix and Java software |
| Weak spot | still several times larger than a good lossy encode | essentially obsolete outside legacy systems |
| Metadata | vorbis comments for tags plus a dedicated PICTURE block for cover art; cue sheets can be embedded for whole-disc rips | an optional annotation field in the header can hold a short text string; no formal tag structure exists |
Pick AU as the output
Select .au in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if AU is selectable, the route is real and validated.
Convert on your device
Press Convert. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid AU file. Outputs keep the original filename with the .au extension.
FLAC to AU questions, answered
Will converting FLAC to AU lose quality?
Both sides are re-encoded, so expect a small generation loss controlled by the quality setting: flac is lossless-oriented and au is lossless-oriented. For visually or audibly transparent results keep quality high; for smaller files lower it and compare.
Is it private to convert FLAC files here?
Yes — the .flac file is processed inside your browser tab and never uploaded. The transcode runs on an FFmpeg engine compiled to WebAssembly, so the audio never leaves your device. Close the tab and the file is gone from memory.
Where will the AU file work?
Audio tools such as Audacity, sox, and ffmpeg open .au readily, and Java's sound APIs still accept it. Consumer players, phones, and browsers dropped meaningful support long ago, so conversion to WAV or MP3 is the practical route.
Will the AU file be bigger or smaller than my FLAC?
It depends on the content: a 24-byte header carries a '.snd' magic number, data offset, encoding type, sample rate, and channel count. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my FLAC file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, vorbis comments for tags plus a dedicated PICTURE block for cover art; cue sheets can be embedded for whole-disc rips; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert AU back to FLAC?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .flac → .au → .flac is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.