# Convert MP4 to AU

> Convert MP4 to AU online for free. Runs entirely in your browser, so your files never leave your device. Fast batch conversion, no sign-up, no watermarks.

URL: https://www.converterrr.com/mp4-to-au

- Runs in the browser with FFmpeg (WASM): files are not uploaded, and no credits are used.
- Engines: FFmpeg (WASM) (browser), FFmpeg (cloud).
- API: available. `POST /api/v1/jobs` with `"output_format": "au"` (paid plans).
- More: [Video converter](https://www.converterrr.com/video-converter), [MP4 converter](https://www.converterrr.com/mp4-converter), [Compress MP4](https://www.converterrr.com/compress-mp4).

## How to convert MP4 to AU

1. **Add your MP4 files.** Drag and drop MP4 files onto the converter, paste them, or click to browse. You can add several at once.
2. **Choose AU.** AU is already selected. Open Options if you want to change quality, size or metadata.
3. **Convert.** Click Convert. Your files are converted right in your browser in seconds.
4. **Download your AU.** Download each AU file, or everything at once as a ZIP.

## Good to know

- Only the audio track is kept — the result is an AU file you can play anywhere. Use Options to pick a bitrate.
- MP4 files are typically used for sharing, streaming and uploading video anywhere, while AU is best for legacy Unix and Java applications.
- This conversion runs on FFmpeg (WASM), running locally in your browser — nothing is uploaded and it works even on slow connections.

## MP4 vs AU

|  | MP4 | AU |
| --- | --- | --- |
| Full name | MPEG-4 Part 14 | Sun Audio |
| Type | Video | Audio |
| Extensions | .mp4 | .au |
| MIME type | video/mp4 | audio/basic |
| Best for | sharing, streaming and uploading video anywhere | legacy Unix and Java applications |
| Properties | lossy compression, open standard | legacy format |

**MP4:** MP4 is the most widely supported video container. It usually holds H.264 or H.265 video with AAC audio and plays on every device and platform.

**AU:** AU is a simple audio format introduced by Sun Microsystems, common on early Unix systems and Java.

## Related conversions

- [MP4 to MP3](https://www.converterrr.com/mp4-to-mp3) (in the browser)
- [MP3 to AU](https://www.converterrr.com/mp3-to-au) (in the browser)
- [MP4 to WebP](https://www.converterrr.com/mp4-to-webp) (in the browser)
- [MP4 to MOV](https://www.converterrr.com/mp4-to-mov) (in the browser)
- [WAV to AU](https://www.converterrr.com/wav-to-au) (in the browser)
- [MP4 to GIF](https://www.converterrr.com/mp4-to-gif) (in the browser)
- [MOV to AU](https://www.converterrr.com/mov-to-au) (in the browser)
- [MP4 to WAV](https://www.converterrr.com/mp4-to-wav) (in the browser)
- [M4A to AU](https://www.converterrr.com/m4a-to-au) (in the browser)
- [MP4 to WebM](https://www.converterrr.com/mp4-to-webm) (in the browser)
- [WebM to AU](https://www.converterrr.com/webm-to-au) (in the browser)
- [MP4 to MKV](https://www.converterrr.com/mp4-to-mkv) (in the browser)

## Convert MP4 to other formats

[MP4 to MP3](https://www.converterrr.com/mp4-to-mp3), [MP4 to WebP](https://www.converterrr.com/mp4-to-webp), [MP4 to MOV](https://www.converterrr.com/mp4-to-mov), [MP4 to GIF](https://www.converterrr.com/mp4-to-gif), [MP4 to WAV](https://www.converterrr.com/mp4-to-wav), [MP4 to WebM](https://www.converterrr.com/mp4-to-webm), [MP4 to MKV](https://www.converterrr.com/mp4-to-mkv), [MP4 to M4A](https://www.converterrr.com/mp4-to-m4a), [MP4 to AVI](https://www.converterrr.com/mp4-to-avi), [MP4 to FLAC](https://www.converterrr.com/mp4-to-flac), [MP4 to AAC](https://www.converterrr.com/mp4-to-aac), [MP4 to OGG](https://www.converterrr.com/mp4-to-ogg), [MP4 to WMV](https://www.converterrr.com/mp4-to-wmv), [MP4 to Opus](https://www.converterrr.com/mp4-to-opus), [MP4 to M4V](https://www.converterrr.com/mp4-to-m4v), [MP4 to FLV](https://www.converterrr.com/mp4-to-flv), [MP4 to MPEG](https://www.converterrr.com/mp4-to-mpeg), [MP4 to 3GP](https://www.converterrr.com/mp4-to-3gp), [MP4 to WMA](https://www.converterrr.com/mp4-to-wma), [MP4 to TS](https://www.converterrr.com/mp4-to-ts), [MP4 to MPG](https://www.converterrr.com/mp4-to-mpg), [MP4 to AIFF](https://www.converterrr.com/mp4-to-aiff), [MP4 to AMR](https://www.converterrr.com/mp4-to-amr), [MP4 to VOB](https://www.converterrr.com/mp4-to-vob)

## Convert other formats to AU

[MP3 to AU](https://www.converterrr.com/mp3-to-au), [WAV to AU](https://www.converterrr.com/wav-to-au), [MOV to AU](https://www.converterrr.com/mov-to-au), [M4A to AU](https://www.converterrr.com/m4a-to-au), [WebM to AU](https://www.converterrr.com/webm-to-au), [FLAC to AU](https://www.converterrr.com/flac-to-au), [MKV to AU](https://www.converterrr.com/mkv-to-au), [AAC to AU](https://www.converterrr.com/aac-to-au), [AVI to AU](https://www.converterrr.com/avi-to-au), [OGG to AU](https://www.converterrr.com/ogg-to-au), [WMV to AU](https://www.converterrr.com/wmv-to-au), [Opus to AU](https://www.converterrr.com/opus-to-au), [WMA to AU](https://www.converterrr.com/wma-to-au), [FLV to AU](https://www.converterrr.com/flv-to-au), [M4V to AU](https://www.converterrr.com/m4v-to-au), [MPEG to AU](https://www.converterrr.com/mpeg-to-au), [3GP to AU](https://www.converterrr.com/3gp-to-au), [AIFF to AU](https://www.converterrr.com/aiff-to-au), [AMR to AU](https://www.converterrr.com/amr-to-au), [MPG to AU](https://www.converterrr.com/mpg-to-au), [TS to AU](https://www.converterrr.com/ts-to-au), [M4B to AU](https://www.converterrr.com/m4b-to-au), [MTS to AU](https://www.converterrr.com/mts-to-au), [VOB to AU](https://www.converterrr.com/vob-to-au)

## MP4 to AU: frequently asked questions

### How do I convert MP4 to AU?

Drop your MP4 file onto the converter above, make sure AU is selected, and click Convert. When it's done, download the AU file — it usually takes a few seconds.

### Is it safe to convert MP4 to AU here?

Yes. MP4 to AU conversion happens entirely inside your browser using WebAssembly, so your file is never uploaded to any server.

### Is the MP4 to AU converter free?

Yes — free with no watermark. Signed-out visitors can convert 25 files a day, and a free account raises that to 250.

### Will converting MP4 to AU reduce quality?

No — AU preserves the content of your MP4 file as faithfully as the format allows.

### Can I convert multiple MP4 files at once?

Yes. Add up to 5 files at a time without an account, 10 with a free account and up to 500 on paid plans, then download them individually or as a single ZIP.