Convert AU to AAC
Free online AU to AAC converter. No signup required.
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Max file size: 100 MB
When to convert AU to AAC
Use this conversion when your destination needs AAC and you have a AU source. Keep the original so you can compare the result or try another supported format.
Audio is decoded and re-encoded using format-specific defaults. Sample format and some metadata may change. Embedded cover art is omitted. A lossless destination cannot recover detail lost in the source.
AU vs AAC: Format Comparison
Side-by-side comparison of the source and target formats.
| Property | AU (Source) | AAC (Target) |
|---|---|---|
| Extension | .au | .aac |
| Full Name | Sun AU Audio | AAC Audio |
| Compression | Varies | Lossy |
| File Size | Varies | Small |
| Best For | Unix and Solaris system audio and sound effects | Apple ecosystem audio including iTunes and Ap… |
| Browser Support | Varies | Universal |
How to Convert AU to AAC
Follow these simple steps to convert your file in seconds.
Choose a AU file
Select or drop one file up to 100 MB. Its extension must match this converter. Availability is checked before transfer.
Convert to AAC
Audio is decoded and re-encoded using format-specific defaults. Sample format and some metadata may change. Embedded cover art is omitted. A lossless destination cannot recover detail lost in the source.
Download and check the result
Use Download after conversion completes. Open the result and check its content, quality and formatting before sharing it. Download links expire one hour after upload finishes. Uploaded and converted files are removed automatically by regular cleanup. Files may become unavailable sooner when the service restarts.
Tips for Converting AU to AAC
Practical advice to get the best results from this conversion.
Why this conversion is worth doing
Sun AU Audio has a known limitation: largely obsolete for general-purpose audio use. AAC Audio addresses this with a key advantage: better audio quality than MP3 at the same bitrate. Converting from AU to AAC is most worthwhile when this specific trade-off matters for the way you intend to use the file.
Match the format to the actual workflow
Sun AU Audio is most commonly used for unix and solaris system audio and sound effects, while AAC Audio is the standard for apple ecosystem audio including itunes and apple music. If your workflow is closer to the second pattern, converting makes sense. If you are still working in a context where AU is the norm, converting may create unnecessary compatibility friction with collaborators or tools that expect the source format.
Watch for this limitation in the AAC output
AAC Audio has its own limitation worth understanding before you commit: lossy compression permanently removes audio information. After the conversion completes, open the AAC file and verify that this limitation does not affect your specific use case — for some workflows it is irrelevant; for others it can be a deal-breaker.
Understand lossy vs. lossless before converting
Converting from a lossy format like MP3 to a lossless format like FLAC or WAV does not restore lost audio data — it only changes the container. If you need true lossless quality, always start from an uncompressed or lossless source. Converting lossless to lossy, however, is a valid way to reduce file size for streaming or mobile playback.
Understanding AU and AAC Formats
Learn about the source and target file formats to understand what happens during conversion.
Source Format
Sun AU Audio
audio/basicAU is an audio file format introduced by Sun Microsystems and commonly associated with Unix and NeXT systems. It supports various encodings including uncompressed PCM, mu-law, and A-law compression, with a simple header structure. AU was one of the earliest audio formats supported on the web and remains used in Unix-based audio programming.
Advantages
- Simple, well-documented format with a minimal header
- Native support in Unix, Solaris, and Java audio APIs
- Supports multiple encoding types including mu-law for telephony
Limitations
- Largely obsolete for general-purpose audio use
- Limited metadata support and no modern compression options
- Poor support in consumer audio software and devices
Common Uses
- Unix and Solaris system audio and sound effects
- Java application audio playback (javax.sound)
- Legacy telephony and voice processing systems
Target Format
AAC Audio
audio/aacAAC (Advanced Audio Coding) is a lossy audio compression standard designed as the successor to MP3, offering better sound quality at equivalent bitrates. It is the default audio format for Apple devices, YouTube, and many streaming platforms. AAC supports sample rates from 8 to 96 kHz and up to 48 channels of audio.
Advantages
- Better audio quality than MP3 at the same bitrate
- Default format for iTunes, Apple Music, YouTube, and many streaming services
- Supports multi-channel audio up to 48 channels
Limitations
- Lossy compression permanently removes audio information
- Slightly less universal hardware support compared to MP3
- Patent-encumbered format with licensing requirements for encoders
Common Uses
- Apple ecosystem audio including iTunes and Apple Music
- YouTube and streaming platform audio encoding
- Mobile audio content and digital broadcasting
Frequently Asked Questions
Common questions about converting AU to AAC.
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