MP3 Won't Open? Convert to AU Instantly
Fast, instant MP3 to AU conversion. No signup required. Just drop your .mp3 file and get .au in seconds.
Batch Settings
お気に入りの音楽や大切な音声データ、MP3形式で保存されていることが多いですよね。しかし、特定の業務用システムや、古いながらも信頼性の高いオーディオ機器では、AU形式が求められる場面も少なくありません。特に、音質の劣化を最小限に抑えつつ、安定した再生環境を構築したいと考えるプロフェッショナルな方々にとって、この変換は非常に重要です。当社のMP3からAUへの変換ツールは、複雑な設定なしに、どなたでも簡単に高品質な変換を実現できるよう設計されています。大切な音源を、必要なフォーマットで、最適な環境でお使いいただくための一助となれば幸いです。
- アニメ制作での効果音
- ビジネス会議録のアーカイブ
- 伝統芸能の音源保存
日本では、一部の放送局や研究機関でAU形式が未だ現役で利用されており、特に専門分野での需要が見られます。汎用性は低いものの、その堅牢性が評価されている側面もあります。
About MP3 to AU Conversion
Dealing with a MP3 file that won't open on your device? You're not alone — MP3 compatibility issues are one of the most common reasons people search for a file converter. MP3 is the universal audio format — high compression, wide compatibility, ideal for music and podcasts.
The fix is simple: convert your MP3 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 MP3 to AU maintains high quality with CocoConvert's optimised encoder settings.
CocoConvert processes your MP3 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 MP3 to AU
- 1
Add your MP3 file
Drag and drop your .mp3 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 MP3 to AU
Your MP3 file is decoded and re-encoded as AU.
Your MP3 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
MP3
.mp3 file
| Extension | .mp3 |
| MIME Type | audio/mpeg |
| Category | Audio |
AU
.au file
| Extension | .au |
| MIME Type | audio/basic |
| Category | Audio |
Should You Convert MP3 to AU?
When to Convert
- ✓When you need a AU file
Frequently Asked Questions
Why won't my MP3 file open?
MP3 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 MP3 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 MP3 to AU?
Converting MP3 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 MP3 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 MP3 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.