Free online AU to GSM converter
Convert AU audio to GSM speech format with FFmpeg or 101convert.com
Convert AU to GSM online - free
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How to convert au to gsm file
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Source format
AU is a simple audio file format originally associated with Sun Microsystems and early Unix systems. It is often used for basic sound clips, legacy software, and older audio archives. AU files may contain uncompressed PCM audio or compressed variants, and they are commonly encountered in technical environments, older multimedia projects, and some Unix-based tools.
Target format
GSM is a speech-oriented audio format based on the GSM 06.10 codec. It is designed for low-bitrate voice audio, making it useful for telephony, voicemail systems, and other applications where small file size matters more than high fidelity. Compared with AU, GSM is typically much smaller but also much more limited in sound quality and frequency range.
How to perform the conversion
The most reliable way to convert AU to GSM is with FFmpeg, which supports both formats and is widely available on Windows, macOS, and Linux.
- Install FFmpeg if it is not already available on your system.
- Open a terminal or command prompt in the folder containing your AU file.
- Run a command such as
ffmpeg -i input.au -ar 8000 -ac 1 -c:a gsm output.gsm. - Check the resulting file in an audio player or by playing it back in the target system.
If you prefer a graphical workflow, some desktop audio editors or converters can open AU files and export to GSM, but support for GSM export is less common than for mainstream formats. In that case, look for an export option such as File → Export or File → Save As, then choose GSM if it is available.
You can also convert the file on 101convert.com for free, without installing any software.
Notes on quality and compatibility
AU to GSM is a lossy conversion. If the source AU file contains music, stereo audio, or higher sample rates, the result will lose detail because GSM is optimized for speech. For best compatibility, convert to 8 kHz, mono, and a speech-friendly bitrate, since many GSM decoders expect telephony-style audio.
Not every AU file is identical: some use different encodings or sample formats, so a few older files may need preprocessing before conversion. If FFmpeg has trouble reading the file, try inspecting it first with ffprobe input.au. Also note that GSM support is less common in modern players than formats like MP3 or WAV, so the converted file may be intended mainly for legacy systems or specialized voice applications.
Note: This au to gsm conversion record is incomplete, must be verified, and may contain inaccuracies. Please vote below whether you found this information helpful or not.
Frequently asked questions
Is the AU to GSM converter free?
Yes, converting AU to GSM on 101convert.com is completely free. No registration, email address or installation is required.
How large can my AU file be?
You can upload AU files up to 1000 MB and convert up to 100 files at once in a single batch.
What happens to my uploaded files?
Files are processed automatically and deleted from our servers within a few minutes after conversion. We never view or share your files.
Do I need to install any software to convert AU to GSM?
No. The AU to GSM conversion runs entirely online in your browser and works on Windows, Mac, Linux, Android and iPhone.
Did the conversion fail?
In most cases, the cause is an incorrect file format. Please upload a valid AU file for this AU to GSM conversion. Occasionally, the issue may be on our side. We analyze recurring conversion failures and disable or fix the converter if we detect a defect.