FixFile
File Format

AAC (.aac)

Advanced Audio Coding — the successor to MP3, delivering better sound quality at equivalent bitrates. Default audio format for Apple, YouTube, and most streaming services.

Extension
.aac
MIME Type
audio/aac

Last updated

Overview

AAC (Advanced Audio Coding) is a lossy audio compression format standardised by ISO/IEC in 1997. It was designed as the direct successor to MP3, achieving the same perceived audio quality at roughly 30% lower bitrates. A 128 kbps AAC file sounds comparable to a 192 kbps MP3 to most listeners.

AAC is the dominant format for digital audio distribution. Apple uses it as the default for the iTunes Store, Apple Music, and iPhone audio. YouTube, Netflix, and most podcast platforms deliver AAC. When paired with the MPEG-4 container (.m4a extension), it also supports chapter markers and cover art.

Common Uses

  • Music streaming — Apple Music, Spotify (AAC at 256 kbps), YouTube Music
  • Podcast distribution — widely accepted and efficient for spoken-word content
  • Mobile audio — default recording format on iPhone and many Android devices
  • Video soundtracks — AAC is the required audio codec for MP4 and HLS video streams

Advantages

  • Better quality than MP3 — perceptually superior at the same bitrate due to more efficient psychoacoustic model
  • Broad hardware support — natively supported on iOS, Android, macOS, Windows, and all major streaming platforms
  • Efficient streaming — low bitrate options (64–96 kbps) remain acceptable quality for speech and podcasts
  • Container flexibility — works inside MP4, M4A, TS, and ADTS containers

Limitations

  • Lossy compression — audio data is permanently discarded; not suitable for archival or further processing
  • Patent history — historically required licensing; now more open but some implementations vary
  • Not universally lossless — unlike FLAC or WAV, decoding does not recover the original waveform

Supported Software

  • Apple: iTunes, Music, QuickTime, Final Cut Pro, Logic Pro
  • Cross-platform: VLC, foobar2000, Windows Media Player, Audacity (with FFmpeg)
  • Mobile: Native iOS/Android media players, Spotify, Apple Music, YouTube Music

Tools for AAC files