Free online AIFF to AU converter

Legacy Unix, Sun Audio, Java, and telephony software may require an .au file instead of AIFF. Converting an AIFF recording also allows you to create the 8 kHz mono μ-law audio expected by many older voice systems, although that setting reduces fidelity.

What the AIFF format is

AIFF (Audio Interchange File Format) is an audio container developed by Apple and commonly used for uncompressed PCM recordings. It usually stores big-endian linear PCM, such as 16-bit stereo at 44.1 or 48 kHz, along with metadata and sample data. Audio editors, digital audio workstations, Apple software, and some samplers use AIFF; older Mac workflows may use the related .aif extension. AIFF is often lossless, but the container can also hold compressed audio, so the extension alone does not guarantee a specific codec.

What the AU format is

AU, also called Sun Audio, is a container identified by .au and a header that records the encoding, sample rate, channel count, and data length. It was used by Sun systems, Unix tools, early Java audio applications, and older web and telephony software.

Traditional AU speech files commonly use 8-bit μ-law at 8,000 Hz in mono. AU can also contain linear PCM, including 16-bit big-endian PCM, so it can retain high-quality audio when the receiving application supports that encoding. Uncompressed PCM AU is not inherently smaller than AIFF; μ-law AU is smaller because it uses 8-bit companded samples.

How to convert an AIFF file to AU

Using FFmpeg

FFmpeg is suitable when you need to control the AU codec, sample rate, channels, or bit depth. Install FFmpeg from a trusted package source, open a terminal in the folder containing the AIFF file, and run a command that matches the target software.

For a broadly compatible 16-bit PCM AU file, retain the source sample rate and channel layout with:

ffmpeg -i input.aiff -c:a pcm_s16be output.au

This creates big-endian 16-bit PCM. Replace the filenames as needed; quote names containing spaces, for example:

ffmpeg -i 'Field recording.aiff' -c:a pcm_s16be 'Field recording.au'

For the traditional telephone-oriented AU variant, resample and downmix the recording before encoding μ-law:

ffmpeg -i input.aiff -ar 8000 -ac 1 -c:a pcm_mulaw output.au

The second command is appropriate for speech systems that explicitly require 8 kHz mono μ-law. It is not appropriate for music preservation.

Using 101convert

On 101convert.com, select the AIFF file, choose AU as the output format, start the conversion, and download the resulting .au file without installing software. Use desktop software such as FFmpeg when the source is confidential or the destination requires a specific AU encoding, sample rate, channel count, or bit depth.

Quality and compatibility limits

Changing an AIFF file to AU does not inherently reduce quality if the output remains linear PCM with the same sample rate, channel count, and bit depth. The μ-law option is lossy: it is designed for speech, reduces high-frequency detail, and should not be used for archival or high-fidelity music files.

Confirm the receiving program’s requirements rather than relying only on the .au extension. Some applications accept only μ-law, mono audio at 8 kHz; others support PCM AU. Renaming an AIFF file to .au does not convert its container or byte order.

Check the result with ffprobe output.au or an audio editor, verifying the codec, sample rate, channel count, bit depth, and duration.