AU to AAC Converter
Convert AU to AAC online for free. Fast, secure, and high-quality conversion with no sign-up or software required.
Maximum file size is 1GB
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Three steps to your converted file
Everything happens in your browser tab - upload, pick a format, download. The heavy lifting runs on our servers.
Upload your file
Drag and drop, click to browse, or paste a URL. Batches take up to 20 files at once - 230+ input formats across video, audio, image, document, and archive types.
Choose an output format
Pick from over a hundred output formats. Filter by category or search by name - every option is open to everyone, no account needed.
Convert & download
Hit Convert and grab your download link moments later. Originals are erased when the job completes; results are cleared within about an hour.
What is an AU file?
The AU file format is a simple container format introduced by Sun Microsystems and NeXT for UNIX-based systems. It typically contains μ-law (mu-law) logarithmic encoded audio data (G.711 standard) stored in a big-endian byte order, identified by the hexadecimal magic number 0x2e736e64 ('.snd'). The file structure consists of a minimal 24-byte header specifying data offset, sample rate, and encoding type, followed by an optional annotation block and the contiguous audio data, making it a standard for early Web audio (Java applets) and SPARCstation workstations.
How to open an AU file
Modern operating systems often lack direct associations for AU files due to their obsolescence. While some Linux distributions and macOS (via Core Audio) may support basic playback, Windows requires third-party software. The VLC media player is the primary recommendation for opening AU files across all platforms; alternatively, Audacity can be used to import the raw data and convert it to modern PCM formats like WAV.
AU Technical Info
- Full Name
- Sun Microsystems Audio
- Developed By
- Sun Microsystems / NeXT
- Initial Release
- 1988
- MIME Type
- audio/basic
What is an AAC file?
Advanced Audio Coding (AAC) is a lossy digital audio compression standard defined by ISO/IEC 13818-7 (MPEG-2) and ISO/IEC 14496-3 (MPEG-4). Developed by a consortium including Bell Labs, Fraunhofer IIS, and Dolby Laboratories as the successor to MP3, AAC utilizes the Modified Discrete Cosine Transform (MDCT) algorithm and perceptual noise shaping to discard imperceptible signal components. It supports up to 48 audio channels, arbitrary sample rates, and utilizes extensions such as Spectral Band Replication (SBR) to achieve higher fidelity at lower bitrates than predecessor formats.
How to open an AAC file
AAC serves as the default audio container for Apple's iTunes and iOS devices, ensuring native support within the macOS Core Audio framework and Apple Music. Windows 10 and 11 provide native decoding support via the Groove Music and Windows Media Player applications. For cross-platform playback or advanced stream analysis, users should utilize VLC Media Player or FFmpeg, which contain the necessary libavcodec libraries to decode AAC streams without external codec packs.
AAC Technical Info
- Full Name
- Advanced Audio Coding
- Developed By
- Bell Labs, Fraunhofer IIS, Dolby, Sony, Nokia
- Initial Release
- 1997
- MIME Type
- audio/aac
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The fastest way to convert any file
Purpose-built for speed, privacy, and breadth of format support.
Convert AU to AAC in seconds
Every AU to AAC conversion runs on our servers, so your device stays fast and the output quality stays intact.
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No queue, no waiting. Files are processed on high-performance servers and returned in seconds, even for large files.
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Encrypted in transit and never shared with anyone. Uploads are erased the moment your job completes, and results shortly after.
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Developer API
Convert AU to AAC via API
Automate AU to AAC conversions in three steps: create a job, upload your file, then poll for the result.
# 1. Create job
curl -X POST https://api.runconvert.com/v3/jobs \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"tag": "au-to-aac",
"tasks": {
"upload-file": {
"operation": "import/upload"
},
"convert": {
"operation": "convert",
"input": "upload-file",
"output_format": "aac"
},
"export-result": {
"operation": "export/url",
"input": "convert"
}
}
}'
# 2. Upload your file (use upload_url from the response)
curl -X PUT "$UPLOAD_URL" --upload-file input.au
# 3. Poll for result
curl https://api.runconvert.com/v3/jobs/$JOB_ID?include=tasks \
-H "Authorization: Bearer YOUR_API_KEY"Replace YOUR_API_KEY with your RunConvert API key. Get your free API key at runconvert.com/api.