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 WMA
Re-encoding .au audio as .wma 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 Windows Media audio
Re-encoding .au audio as .wma 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.
A .wma file contains Windows Media Audio, Microsoft's proprietary compressed format, wrapped in the same ASF container as WMV video. It shipped with every copy of Windows for a decade, so ripped CDs and store purchases from that era survive as .wma libraries. For this route the practical draw is respectable quality at mid bitrates for its era and still opens on any Windows PC without extra software — balanced against proprietary and effectively abandoned, which is worth knowing before you commit a large batch.
Why convert AU to WMA?
The practical trigger for this conversion is usually a mismatch: with .au, essentially obsolete outside legacy systems. Switching to .wma buys you respectable quality at mid bitrates for its era, which is why it is the better fit for converting old ripped-CD libraries to MP3 or FLAC. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
AU vs WMA at a glance
| Aspect | Sun audio (.au) | Windows Media audio (.wma) |
|---|---|---|
| Format type | Lossless — every pixel or sample is preserved exactly | Lossy — discards detail it judges invisible to shrink files |
| How it stores data | a 24-byte header carries a '.snd' magic number, data offset, encoding type, sample rate, and channel count | the standard codec is a lossy transform coder supporting up to 48 kHz stereo |
| Strongest at | maintaining sound assets in vintage Unix and Java software | converting old ripped-CD libraries to MP3 or FLAC |
| Weak spot | essentially obsolete outside legacy systems | proprietary and effectively abandoned |
| Metadata | an optional annotation field in the header can hold a short text string; no formal tag structure exists | aSF attributes mirror ID3 basics such as title, artist, album, and artwork, and Windows Media Player wrote extended library fields on top |
Pick WMA as the output
Select .wma in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if WMA 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 WMA file. Outputs keep the original filename with the .wma extension.
AU to WMA questions, answered
Will converting AU to WMA lose quality?
Some. Since au is lossless-oriented and wma is lossy-oriented, the encoder will discard detail it judges least visible; the quality slider controls how aggressive that is. Keep the original .au if you may need a pristine master later.
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 WMA file work?
Windows continues to play .wma through its bundled apps, but macOS, iOS, Android, and all web browsers lack native support. Files protected by Windows Media DRM will not play anywhere now that their license servers are gone.
Will the WMA file be bigger or smaller than my AU?
Smaller, usually dramatically so — that is the main reason this route exists. The quality slider trades size against fidelity; the default sits at the point where most people cannot spot the difference.
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 WMA back to AU?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .au → .wma → .au is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.