AAC (Advanced Audio Codec)
Definition
A lossy audio compression codec used by Apple Music, YouTube, Spotify, and most major streaming platforms. At equivalent bitrates, AAC generally produces better quality than MP3. Standard streaming quality is 256 kbps AAC.
In Simple Terms
The format most streaming platforms use to deliver your music. When you upload a WAV, platforms convert it to AAC — that's what listeners actually hear.
In Practice
Apple Music delivers standard quality streams as 256 kbps AAC and lossless as ALAC. Understanding the codec helps engineers make informed mastering decisions for streaming delivery.
Common Confusion
AAC is a codec, not a file format. It can be contained in MP4, M4A, or other containers. The file extension does not always reveal the codec.
Sources & Verification
- ISO/IEC 14496-3:2019 — Advanced Audio Coding (AAC) specificationInternational Organization for Standardization, 2019
- Brandenburg, K. — MP3 and AAC explainedAES 17th International Conference, 1999
- Apple Music — Audio formats and deliveryApple Music for Artists
Last verified: 2026-05-05