AAC Won't Open? Convert to AU Instantly
Fast, instant AAC to AU conversion. No signup required. Just drop your .aac file and get .au in seconds.
Batch Settings
About AAC to AU Conversion
Dealing with a AAC file that won't open on your device? You're not alone — AAC compatibility issues are one of the most common reasons people search for a file converter. AAC (Advanced Audio Coding) offers better quality than MP3 at the same bitrate — the default codec for Apple devices.
The fix is simple: convert your AAC to AU. AU is a widely used file format. This conversion lets you convert between formats quickly, solving the problem in seconds rather than hours of troubleshooting.
Converting AAC to AU maintains high quality with CocoConvert's optimised encoder settings.
CocoConvert processes your AAC file on secure servers in Germany — upload, convert, download. Your files are encrypted via TLS and automatically deleted within 24 hours. No account needed, no software to install, and it works on any device with a browser.
This conversion is ideal when you When you need a AU file.
The conversion engine behind CocoConvert uses FFmpeg, Sharp, and qpdf — the same open-source libraries trusted by Netflix, YouTube, and enterprise platforms. Pro users can batch convert up to 100 files at once.
How to Convert AAC to AU
- 1
Add your AAC file
Drag and drop your .aac file into the converter, or tap "Browse" to pick it from your device. Multiple files are supported for batch processing.
- 2
Pick AU output
Select .au as the target format. CocoConvert automatically applies the best quality settings for this conversion.
- 3
Start conversion
Hit the Convert button. The audio engine processes your file server-side — no CPU drain on your device.
- 4
Save your file
Once done, download your .au file. For batch jobs, download all at once as a zip.
What Happens When You Convert AAC to AU
Your AAC file is decoded and re-encoded as AU.
Your AAC file is uploaded and validated
The file is decoded (parsed into its raw data)
The data is re-encoded in AU format
The converted file is ready for download
Format Comparison
AAC
.aac file
| Extension | .aac |
| MIME Type | audio/aac |
| Category | Audio |
AU
.au file
| Extension | .au |
| MIME Type | audio/basic |
| Category | Audio |
Should You Convert AAC to AU?
When to Convert
- ✓When you need a AU file
Frequently Asked Questions
Why won't my AAC file open?
AAC files may not open if your device lacks the right codec or application. Converting to AU — a more widely supported format — usually resolves this. AU is a widely used file format.
Is it safe to convert AAC to AU online?
Yes. CocoConvert encrypts your file via TLS, processes it on isolated servers in Germany, and permanently deletes it within 24 hours. Your files are never shared or analysed.
Will I lose quality converting AAC to AU?
Converting AAC to AU maintains high quality with CocoConvert's optimised encoder settings. CocoConvert uses high-quality encoder defaults to preserve as much fidelity as possible.
How large can my AAC file be?
Free users can convert files up to 250 MB each. Pro users get a 5 GB limit per file, and Business API users have custom limits.
Can I convert AAC to AU on my phone?
Absolutely. CocoConvert works in any modern browser — iOS Safari, Android Chrome, and all desktop browsers. No app required.
Versions are pinned in our worker Dockerfile and re-built via CI on every change.