Add your AU file
Drop one or more .au 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.
AU to ALAC
Re-encoding .au audio as .alac 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 AU 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 Sun audio to Apple Lossless audio
Re-encoding .au audio as .alac changes how the sound is compressed and which players will accept it. 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.
ALAC, the Apple Lossless Audio Codec, compresses music with zero quality sacrifice, and the .alac extension is occasionally used to label such files explicitly even though the codec normally travels inside an .m4a container. Decoding reproduces the original samples exactly, making it Apple's counterpart to FLAC. For this route the practical draw is native on every Apple platform from iOS to HomePod and mathematically lossless reconstruction — balanced against compresses slightly worse than FLAC on average, which is worth knowing before you commit a large batch.
Why convert AU to ALAC?
The practical trigger for this conversion is usually a mismatch: with .au, essentially obsolete outside legacy systems. Switching to .alac buys you native on every Apple platform from iOS to HomePod, which is why it is the better fit for building a lossless library that syncs cleanly to iPhones and the Music app. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
AU vs ALAC at a glance
| Aspect | Sun audio (.au) | Apple Lossless audio (.alac) |
|---|---|---|
| Format type | Lossless — every pixel or sample is preserved exactly | Lossless — every pixel or sample is preserved exactly |
| How it stores data | a 24-byte header carries a '.snd' magic number, data offset, encoding type, sample rate, and channel count | linear-prediction compression conceptually similar to FLAC, typically reaching 40 to 60 percent of PCM size |
| Strongest at | maintaining sound assets in vintage Unix and Java software | building a lossless library that syncs cleanly to iPhones and the Music app |
| Weak spot | essentially obsolete outside legacy systems | compresses slightly worse than FLAC on average |
| Metadata | an optional annotation field in the header can hold a short text string; no formal tag structure exists | inherits the full iTunes metadata atom set from its MPEG-4 container, including artwork, composer, and grouping fields |
Pick ALAC as the output
Select .alac in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if ALAC 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 ALAC file. Outputs keep the original filename with the .alac extension.
AU to ALAC questions, answered
Will converting AU to ALAC lose quality?
Both sides are re-encoded, so expect a small generation loss controlled by the quality setting: au is lossless-oriented and alac is lossless-oriented. For visually or audibly transparent results keep quality high; for smaller files lower it and compare.
Is it private to convert AU files here?
Yes — the .au 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 ALAC file work?
Every Apple device and application plays ALAC natively, and cross-platform players such as VLC and foobar2000 handle it on Windows, Linux, and Android. Outside the Apple world support varies by player, which is why cross-platform archives still tend to favor FLAC.
Will the ALAC file be bigger or smaller than my AU?
It depends on the content: linear-prediction compression conceptually similar to FLAC, typically reaching 40 to 60 percent of PCM size. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my AU 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, an optional annotation field in the header can hold a short text string; no formal tag structure exists; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert ALAC back to AU?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .au → .alac → .au is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.