FSSD to AU Converter
Processing entirely on your device — large files may take a moment.
FSSD is a raw 8-bit audio dump format from early UNIX sound experiments — tiny headers, bare samples. Converting AU to WAV preserves the samples in a format every modern tool reads.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How FSSD compares to AU
| FSSD | AU | |
|---|---|---|
| Compatibility | ffmpeg, archive tools | Legacy Unix tools |
| Best for | Rescuing legacy audio | Old system sounds and recordings |
How to convert FSSD to AU
- 1
Select your files
Drag & drop your FSSD files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to AU". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted AU file individually, or grab everything at once as a ZIP archive.
About the FSSD format
FSSD is a raw 8-bit audio dump format from early UNIX sound experiments — tiny headers, bare samples.
ffmpeg decodes it natively inside your browser — the audio track is re-encoded to your chosen format with nothing ever uploaded.
+ Strengths
- ✓Decoded natively by ffmpeg
- ✓Runs entirely in your browser
- ✓Free, private, no watermarks
! Limitations
- −Legacy niche format
- −Modern tools rarely open it
- −Keep the original for archival round-trips
About the AU format
AU is Sun Microsystems' audio format from the Unix workstation age: a small header followed by µ-law (or PCM) samples. Java's applet era shipped it everywhere, and old Unix sound tooling still emits it.
Modern players increasingly skip it. Converting AU to WAV preserves the samples bit-for-bit while moving the file into universal territory — the standard rescue path for system sounds and old recordings.
+ Strengths
- ✓Simple, lossless sample storage
- ✓Native to old Unix/Java tooling
! Limitations
- −µ-law flavor sounds dated and mono
- −Dropped by modern players
Why convert FSSD to AU?
Converting makes sense where the strengths of AU meet what FSSD cannot give you. Simple, lossless sample storage Meanwhile Legacy niche format One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this FSSD to AU converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for FSSD to AU?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Will converting FSSD to AU reduce audio quality?
If AU is lossless, the output contains everything the FSSD file contains — no further loss is added. If AU is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.
Can I convert a whole folder of FSSD files?
You can select many files at once and they are processed in a single batch. Output files land in one ZIP download when there is more than one result.