Free online AU to WMA converter

A legacy Windows application, media library, or portable player may require WMA and reject an older AU sound file. Converting produces a .wma copy for that target while preserving the original AU file.

What the AU format is

AU is an audio container format associated with Sun Microsystems, NeXT, and Unix-derived systems. Files commonly use the .au extension, sometimes .snd, and begin with a .snd header.

Early AU files often contain 8-bit µ-law audio at 8 kHz, used for Unix workstation sounds, voice prompts, and telephony-like recordings. The container can also hold A-law, PCM, ADPCM, and other encodings, so its sample rate, channel layout, and audio quality vary by file.

AU files occur in older Solaris and Unix software, Java resources, sound-effect collections, and archival recordings. Current players may not recognize AU files or may fail on less common AU codec variants.

What the WMA format is

WMA is Microsoft Windows Media Audio, generally stored in an ASF container with a .wma extension. The most broadly compatible WMA variant is the lossy Windows Media Audio version 2 codec, commonly identified as WMAv2.

WMA supports metadata such as title, artist, album, and track number. At an appropriate bitrate, it can make a PCM source substantially smaller, which is useful only when a Windows-oriented application or older device specifically accepts WMA.

WMA support is strongest in Windows Media Player and legacy Windows software. MP3, AAC, FLAC, and WAV are generally more widely supported by current devices, so use WMA when the receiving program or hardware requires it.

Convert the file

On 101convert.com, upload the AU file, select WMA as the output format, start the conversion, and download the resulting .wma file. The service can be used free without installing software. Keep the AU source until the WMA file has played successfully in the intended application or device.

For local conversion and explicit codec control, FFmpeg can read common AU variants and create a standard WMAv2 file:

ffmpeg -i input.au -c:a wmav2 -b:a 128k output.wma

Replace input.au and output.wma with the actual filenames. Use 64k for speech, 128k for typical music, or 192k only when the target supports it and the source warrants the larger file.

Inspect an unfamiliar AU file before conversion with:

ffprobe input.au

Check the detected codec, sample rate, channel count, and duration. An unusual or unsupported AU encoding may require a current FFmpeg build or another decoder.

Audacity can import many AU files. If WMA is available in its installed export formats, use File → Export Audio, select WMA, set a compatible bitrate, and save the output; otherwise, use FFmpeg.

Quality and compatibility limits

Conversion cannot improve the source. An 8 kHz µ-law AU voice recording remains narrowband and telephone-like when encoded at 128 kbps WMA; use a modest speech bitrate instead of enlarging the file without adding detail.

Standard WMA is lossy, so encoding PCM or other high-quality AU audio to WMA introduces compression loss. Do not repeatedly convert between lossy formats, and retain the original AU file as the archival copy.

For older players, use WMAv2 rather than WMA Pro or WMA Lossless unless the target explicitly supports those codecs. If a device rejects the output, keep the source channel count where possible and try conventional bitrates such as 64k, 96k, or 128k.