AU to M4A converter
A free AU to M4A converter for Sun Audio files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your AU files here
or browse your device · paste with Ctrl+V
Accepts .au, .snd files. You can queue several files; each is processed one after another on your own device.
Your files never leave this device — there is no upload and no server to delete them from.
- 01
Add your AU files
Drop them onto the box above or click to browse. They are read straight from disk — nothing is sent anywhere.
- 02
Check the settings
M4A is already selected. Open the gear icon on any row if you want to change quality, dimensions or codec before converting.
- 03
Download your M4A
Press convert and wait for the row to finish. Convert several files and you can take them all as a single ZIP.
AU
Sun AudioThe Unix system-sound format from Sun Microsystems, usually holding 8-bit mu-law audio. Historically important, practically obsolete.
- Developed by
- Sun Microsystems
- Released
- 1992
- Extension
- .au, .snd
- MIME type
- audio/basic
- Compression
- Lossy or lossless
M4A
MPEG-4 AudioAn MP4 container holding only audio, normally AAC but sometimes lossless ALAC. This is what iTunes rips to and what Apple devices expect, with proper support for cover art and tags.
- Developed by
- Apple / MPEG
- Released
- 2001
- Extension
- .m4a
- MIME type
- audio/mp4
- Compression
- Lossy or lossless
Questions about converting AU to M4A
Is this AU to M4A converter free?
Yes. Converting AU to M4A here is free, with no account, no watermark and no daily quota. The work runs on your own device, so there is no server cost to pass on to you.
Is my AU file uploaded anywhere?
For browser-based pairs, your file is read locally and converted by ffmpeg in this tab. No file payload is uploaded; you may still see analytics and engine downloads in network logs.
Is there a file-size limit for AU to M4A?
There is no imposed upload cap when it runs in-browser, but each conversion still depends on your device and browser memory. Large videos are the first practical limit, then memory-heavy documents or images.
Does converting AU to M4A lose quality?
It depends on your selected settings and codec path. Many engines can write either lossy or lossless output for M4A, so you can usually increase quality if this file is your final version.
Can I convert several AU files to M4A at once?
Yes. Drop in several files and each gets its own row; they are processed one after another on your device. You can download them one by one or as one ZIP.
Does AU to M4A work on a phone, Mac or Chromebook?
Most modern browsers on Windows, macOS, Linux, ChromeOS, Android and iOS work. Very large videos are often more reliable on desktop or a browser with more memory.
Why do some conversions take longer on first run?
The conversion engine has to download first. Small codec bundles are fast, while ffmpeg is commonly 12–30 MB; later conversions of similar type use the cached engine.
I converted a file and the output is blank or unusable. What should I check?
Start over with default settings, then change one option at a time (quality, bitrate, page size, or codec) to isolate what changed behavior. If it keeps failing, retry with a smaller file and confirm the source format matches the pair.
Convert other formats to M4A
41 formats can become M4A here.
Convert AU to other formats
A AU file can become any of these.
M4A to AU
The reverse conversion
MP4 to M4A
MP3 to M4A
WAV to M4A
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Trim Audio
Cut a section out of an audio file.…
Normalise Audio
Even out loudness across files so nothing is jarring…