AU to M4A converter
Convert AU to M4A in seconds, free and unlimited. No upload, no sign-up, no watermark: your audio never leaves your device.
Last updated
Quick answer: To convert AU to M4A, add the AU file to the iHateFiles AU to M4A converter and press Convert. The conversion runs in your browser, so the file is never uploaded, and it is free with no sign-up, watermark or size limit. AU is a format most software has stopped opening. M4A is not.
Should you convert AU to M4A?
Do this to make a lossless recording small enough to share or carry around. Keep the AU as the master copy.
AU is lossless and M4A is not
This is the conversion lossy formats were designed for: from up to 10 MB per minute to 1 to 1.9 MB. At 192 kbps or more almost nobody can hear the difference in music. Keep the AU as your master if you might need to convert again.
Where the M4A will play
M4A plays on Apple devices, Android, browsers and most modern players.
AU and M4A side by side
| AU | M4A | |
|---|---|---|
| Inside the file | PCM or µ-law | AAC |
| Compression | Lossless | Lossy |
| Carries sound | Yes | Yes |
| One minute of stereo | up to 10 MB | 1 to 1.9 MB |
| Plays on | Needs converting first | Apple devices, Android, browsers and most modern players |
| Here | Read only | Read and write |
What usually goes wrong
About the AU. Many AU files use 8-bit µ-law companding, which sounds like a telephone. That is how they were recorded, not a conversion fault.
About the M4A. M4A, M4B, M4R and AAC are largely the same thing with different extensions. Renaming usually works, though it is not something to rely on.
How to convert AU to M4A
- Add your AU file. It is read from your disk and stays there.
- Check the settings. The output format is already set to M4A.
- Press convert and the M4A file is saved back to your device.
Questions
How do I convert AU to M4A?
Open this page, add your AU file, and press convert. The file is decoded and re-encoded by your own browser and saved back to your device. Nothing is uploaded.
Is this AU to M4A converter free?
Yes, completely. There is no account, no sign-in, no watermark and no daily limit, because there is no server doing the work. Your own device does it.
Are my files uploaded anywhere?
No. There is no upload endpoint. The conversion runs inside this browser tab, so your file never leaves your device. You can open your browser's network panel and watch: nothing carrying your file is sent.
Is there a file size limit?
No fixed limit. Because the work happens on your machine there is no server quota. The only ceiling is your own device's memory, which for video means very large files may be slow.
Will converting to M4A lose quality?
M4A is a lossy format, so some detail is discarded. The quality control on this page decides how much. The default is set high enough that most people cannot see the difference.
Can I convert several AU files at once?
Yes. Add as many as you like and they are converted one after another, then offered as a single ZIP.