What you should know
AAC (Advanced Audio Coding) was designed in 1997 to succeed MP3. At equal bitrate it preserves highs and transients better, which explains its adoption by Apple, YouTube and most streaming services.
It comes in two forms: the raw .aac file and the .m4a container, which adds metadata and structure. The latter is what iTunes and Apple devices produce.
Strengths
- Better quality than MP3 at equal bitrate, especially below 192 kbps
- Dominant delivery format: streaming, podcasts, video platforms
- Good handling of multiple channels and high frequencies
- Native playback on iOS and most modern browsers
Limitations to know
- Less universal than MP3 on old devices
- Codec licensing is more restrictive than MP3's
- Raw .aac files are misidentified by some players that expect .m4a
- Less flexible than OGG for multiple tracks
When to use it
Prefer AAC when quality at a moderate bitrate matters: podcasts, streaming, an Apple library. For maximum compatibility with old hardware, MP3 remains the default.
Quality, size and compatibility
At 128 kbps, AAC clearly outperforms MP3 at the same rate. As with any lossy format, convert once from the uncompressed source: transcoding AAC to AAC compounds the flaws.
Frequently asked questions
- AAC or MP3, which to choose?
- At equal quality, AAC needs less bitrate. Choose it for modern delivery; choose MP3 if the playback device is old or unknown.
- Are AAC and M4A the same?
- M4A is an MP4 container that usually carries AAC. The music is identical; only the wrapper changes, with extra metadata.