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HomeMP3 vs AU
.mp3
.au

MP3 vs AU

Compare MPEG Audio Layer 3 and Sun Audio formats — understand the key differences and when to use each

Format Overview

MP3

MPEG Audio Layer 3

MP3 (MPEG Audio Layer 3) is the world's most popular audio format, developed by the Fraunhofer Society and standardized as ISO/IEC 11172-3 in 1993. MP3 uses psychoacoustic modeling to discard audio frequencies that are less perceptible to human hearing, achieving compression ratios of 10:1 or better. Bitrates range from 32 kbps (voice quality) to 320 kbps (near-CD quality), with 128-192 kbps being common for music. MP3 supports ID3 metadata tags for song title, artist, album, genre, and album art. The format is universally supported by every music player, smartphone, car stereo, and web browser. While newer codecs like AAC and Opus offer better quality at lower bitrates, MP3 remains the most compatible audio format. MP3 files can also contain variable bitrate (VBR) encoding, which adjusts quality dynamically throughout the track for optimal file size.

.mp3audio

AU

Sun Audio

Sun Audio (.au) is a audio file format.

.auaudio

MP3 vs AU: Feature Comparison

FeatureMP3AU
Full NameMPEG Audio Layer 3Sun Audio
File Extension.mp3.au
Categoryaudioaudio
Free to Convert✓ Yes✓ Yes
Browser Support✓ All Browsers✓ All Browsers
Convert to Each Other✓ Yes✓ Yes

When to Use MP3 vs AU

Use MP3 when you need:

  • •Files in MPEG Audio Layer 3 format for maximum compatibility
  • •Industry-standard audio format support
  • •Wide software and platform compatibility

Use AU when you need:

  • •Files in Sun Audio format for specific workflows
  • •Optimized audio format features
  • •Modern format advantages and smaller file sizes

Convert Between Them

MP3 AUAU MP3
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Learn More About These Formats

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Frequently Asked Questions

What is the difference between MP3 and AU?
MP3 (MPEG Audio Layer 3) and AU (Sun Audio) are both audio file formats. MP3 files use the .mp3 extension while AU uses .au. They differ in compression, quality, compatibility, and intended use cases.
Can I convert MP3 to AU for free?
Yes! Convert999 lets you convert MP3 to AU completely free, directly in your browser. No file upload to any server, no registration needed — your files stay private on your device.
Which is better, MP3 or AU?
It depends on your use case. MP3 (MPEG Audio Layer 3) may be better for certain workflows, while AU (Sun Audio) excels in others. Consider factors like file size, quality, software compatibility, and your specific needs.
Is it safe to convert files on Convert999?
Absolutely. Convert999 processes all files 100% locally in your browser. Your files are never uploaded to any server, ensuring complete privacy and security.

MP3 Converter

Convert from MP3

AU Converter

Convert from AU

File Tools

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Convert to MP3

All sources → MP3

Convert to AU

All sources → AU

Format Statistics

Trends & data 2025

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