Convert anything, at global scale.
200+ formats and automation APIs that feels instant.
CONVERT
From
To
Drop files or choose a source
Upload multiple files at once, mix formats, and fine-tune every conversion with format-aware settings.
Max 2GB per file · Drag & drop ready · Mixed file types welcome
AU at a glance
AU
AU belongs to an earlier multimedia era where workstation and Unix vendors often had their own practical audio defaults.
M4A at a glance
M4A
M4A became familiar through Apple and portable-device music workflows, where extension conventions shaped user expectations about what kind of media file they were dealing with.
Format comparison
| Feature | AU | M4A |
|---|---|---|
| File type | Audio | Audio |
| Extensions |
|
|
| MIME type |
|
|
| Compression / quality | depends | depends |
| File size characteristics | medium | medium |
| Compatibility | broad | broad |
| Editability | limited | limited |
| Created year | 1987 | 2001 |
| Inventor | Sun Microsystems | Apple / MPEG |
| Status | active | active |
| Primary use cases |
|
|
| Common software |
|
|
| Archival suitability | moderate | moderate |
| Metadata handling | moderate | moderate |
| Delivery profile | strong | strong |
| Workflow fit | delivery | delivery |
| Multitrack support | Not supported | Not supported |
| HDR support | Not supported | Not supported |
| Streaming ready | Not supported | Supported |
When to use each format
When to use AU
- capture ingest
- editing and mastering
- streaming or playback delivery
- Historically important in Unix/workstation audio.
When to use M4A
- capture ingest
- editing and mastering
- streaming or playback delivery
- Very common in modern audio libraries.
FAQs
Why convert AU to M4A?
Choose M4A as target when you need a compact, modern audio file for music, podcasts, lectures, or spoken-word distribution with strong playback support and good metadata handling.
What changes when converting AU to M4A?
Convert to M4A when you need a compact, modern audio file for music, podcasts, lectures, or spoken-word distribution with strong playback support and good metadata handling. It is an excellent target for listening copies and portable libraries. For raw editing or mastering, uncompressed or lossless production formats remain better choices.
What should I review after converting AU to M4A?
After conversion, review these destination checks: Open converted output in music apps and verify behavior on real samples; Compare output against the expected depends quality profile; Container identity and codec identity can still be confused.
How can I keep quality stable in AU to M4A conversion?
Run representative samples, keep settings deterministic, and monitor these risks: Its meaning depends on the audio codec inside the file; Container identity and codec identity can still be confused; Validate destination compatibility before large-batch conversion.