MP3 → AU
Convert MP3 audio to AU entirely in your browser — no upload, no watermark, no sign-up.
Drop files here
or browse from your device
images · audio · video · documents · archives · up to ~500MB
Your first conversion lands here automatically — saved on this device only, never uploaded.
100% Private
Runs in your browser. No upload.
Instant
No queue, no server roundtrip.
Offline-ready
Works after first load.
Moving MP3 audio to AU is about compatibility and size — which players accept the file and how much disk or bandwidth it costs once it gets there. AU (Sun audio file) earns its place here: minimal headers that legacy Unix and Java tooling read directly. MP3 is the format that made digital music portable. It is lossy, thirty years old, and still the only audio format you can hand to anyone with total confidence it will play.
MP3 is the format that made digital music portable. It is lossy, thirty years old, and still the only audio format you can hand to anyone with total confidence it will play.
The audio is decoded and re-encoded, so the running time, channels and sample content stay intact while bitrate and file size follow AU. Going from a compressed MP3 file to any other lossy format is a second generation of compression — start from the highest-quality source you have when it matters, and expect a lossless target to grow the file rather than improve the sound.
What you gain with AU: Minimal headers that legacy Unix and Java tooling read directly.
Drop your MP3 file above and Morphio decodes it locally, then re-encodes it as AU using WebAssembly + the browser's native codecs. Nothing is ever uploaded — your files stay on your device. Batch as many files as your machine can handle. See exactly how in-browser conversion works.
Open the MP3 to AU page, drop your audio file on the drop zone and press convert. Morphio runs an FFmpeg build compiled to WebAssembly that runs inside the page, so the MP3 data never leaves your device and no server ever receives a copy.
Sample rate and channel layout carry across, and you keep the original file untouched on disk. Converting MP3 to AU only rewrites the container and encoding you asked for — the source file on your disk is never modified.
Yes. The free plan covers 10 conversions a day with files up to 200 MB and adds no watermark or sign-up. Morphio Pro ($5/month, or $29 once for lifetime access) removes the daily cap and raises the per-file limit to 5 GB.
Morphio decodes the MP3 file at full fidelity and re-encodes it at a high-quality AU setting, so the difference is normally invisible or inaudible. What conversion cannot do is recover detail the original MP3 file already threw away.
Yes — drop the whole batch in and each file is processed in turn on your own machine. The practical limit is your device's memory and patience, not a server quota, because nothing is queued anywhere else.
No. The conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can disconnect from the internet after the page loads and it still works.