GSM to AU Converter
Processing entirely on your device — large files may take a moment.
GSM 06.10 Speech and Sun Microsystems Audio exist for different jobs: GSM 06.10 is the 1990s mobile-telephony speech codec — 13 kbit/s audio that VoIP systems and old answering machines still emit. Converting AU to WAV preserves the samples in a format every modern tool reads.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How GSM compares to AU
| GSM | AU | |
|---|---|---|
| Compatibility | Asterisk, SoX, ffmpeg | Legacy Unix tools |
| Best for | Telephony recordings | Old system sounds and recordings |
How to convert GSM to AU
- 1
Select your files
Drag & drop your GSM 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 GSM format
GSM 06.10 is the speech codec of the original GSM mobile network — 13 kbit/s RPE-LTP that made digital cellphone calls possible in 1991 and still lives inside VoIP systems, old answering machines and Asterisk PBX recordings.
It is lossy speech, not music: converting GSM to WAV or MP3 preserves intelligibility perfectly while finally letting desktop players open the file without special codecs.
+ Strengths
- ✓Tiny bitrate for speech intelligibility
- ✓Ubiquitous in telephony systems
- ✓Decodes natively via ffmpeg
! Limitations
- −Speech-only quality — music falls apart
- −13 kbit/s artifacts are audible
- −8000 Hz sample rate only
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 GSM to AU?
Converting makes sense where the strengths of AU meet what GSM cannot give you. Simple, lossless sample storage Meanwhile Speech-only quality — music falls apart One pass through the converter above puts your file on the right side of that trade-off.
Frequently asked questions
Is this GSM 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 GSM 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 GSM to AU reduce audio quality?
If AU is lossless, the output contains everything the GSM 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 GSM 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.