Audio Formats Reference

Overview

Audio formats fall into three categories: uncompressed (WAV, AIFF), lossless compressed (FLAC, ALAC), and lossy compressed (MP3, AAC, Opus). The choice depends on the balance between file size, audio quality, and compatibility requirements.

Format Comparison

Format	Type	Quality	File Size	Browser Support	Best For
MP3	Lossy	Good	Small	Universal	Music distribution
AAC	Lossy	Very good	Small	Universal	Streaming, mobile
Opus	Lossy	Excellent	Smallest	Chrome, Firefox, Edge, Safari 16+	Voice, music, streaming
OGG Vorbis	Lossy	Very good	Small	Chrome, Firefox, Edge	Open-source projects
FLAC	Lossless	Perfect	Medium	Chrome, Firefox, Edge, Safari 14.1+	Archival, audiophile
WAV	Uncompressed	Perfect	Very large	Universal	Editing, production
AIFF	Uncompressed	Perfect	Very large	Safari	Apple production
ALAC	Lossless	Perfect	Medium	Safari, iTunes	Apple ecosystem
WMA	Lossy/Lossless	Good	Small	Edge	Windows (legacy)
WebM Audio	Lossy	Excellent	Small	Chrome, Firefox, Edge	Web streaming

Detailed Format Breakdown

MP3 (.mp3)

MIME type: audio/mpeg
Bitrates: 128-320 kbps (CBR) or VBR
Sample rates: Up to 48 kHz
Channels: Stereo, joint stereo, mono
Most widely supported audio format
192 kbps+ recommended for music
128 kbps acceptable for speech/podcasts
Patent-free since 2017

AAC (.aac, .m4a)

MIME type: audio/aac or audio/mp4
Bitrates: 64-512 kbps
Sample rates: Up to 96 kHz
Better quality than MP3 at same bitrate
Default format for Apple Music, YouTube
HE-AAC variant for low-bitrate streaming
Widely supported on mobile devices

Opus (.opus)

MIME type: audio/opus
Bitrates: 6-510 kbps
Sample rates: Up to 48 kHz
Best quality-to-size ratio of any lossy codec
Excellent for both speech and music
Low latency, ideal for real-time communication
Used by Discord, WhatsApp, and WebRTC
Royalty-free

OGG Vorbis (.ogg)

MIME type: audio/ogg
Bitrates: 45-500 kbps
Sample rates: Up to 192 kHz
Open-source alternative to MP3/AAC
Better quality than MP3 at similar bitrates
Being superseded by Opus
Used in gaming (Unity, Unreal)

FLAC (.flac)

MIME type: audio/flac
Compression: ~50-60% of original size
Sample rates: Up to 655 kHz
Bit depth: Up to 32-bit
Lossless compression (no quality loss)
Standard for high-fidelity music distribution
Open-source format
Supports embedded metadata and album art

WAV (.wav)

MIME type: audio/wav
Encoding: PCM (uncompressed)
Sample rates: Up to 192 kHz
Bit depth: 16, 24, or 32-bit
Industry standard for audio production
No compression overhead
Very large file sizes
CD quality: 16-bit, 44.1 kHz (10 MB/minute)

Bitrate Guide

Use Case	Recommended Format	Bitrate
Voice/Podcast	Opus or AAC	48-96 kbps
Music streaming (standard)	AAC or Opus	128-192 kbps
Music streaming (high quality)	AAC or Opus	256-320 kbps
Lossless streaming	FLAC	800-1400 kbps
Audio editing	WAV	1411+ kbps (uncompressed)
Web sound effects	MP3 or Opus	128 kbps
Phone calls / VoIP	Opus	16-32 kbps
Background music (web)	AAC or Opus	96-128 kbps

Web Audio Best Practices

<audio controls>
  <source src="audio.opus" type="audio/opus" />
  <source src="audio.aac" type="audio/aac" />
  <source src="audio.mp3" type="audio/mpeg" />
</audio>

Primary: Serve Opus for best quality at smallest size
Fallback: AAC for Safari/iOS compatibility
Legacy fallback: MP3 for universal support
Preload: Use preload="none" or preload="metadata" for performance

Tools

Tool	Type	Use Case
FFmpeg	CLI	Universal audio conversion
Audacity	GUI	Audio editing and export
SoX	CLI	Audio processing and conversion
LAME	CLI	MP3 encoding
opusenc	CLI	Opus encoding
MediaInfo	CLI/GUI	Format inspection and metadata