Audio Format
What Is AAC?
AAC (Advanced Audio Coding) is a lossy audio format developed as the standardised successor to MP3. It produces better sound quality at the same file size — or smaller files at equal quality. It is the default audio format on Apple devices and the standard for most streaming platforms.
Key facts
- Type
- Lossy compressed
- File extensions
- .aac, .m4a, .mp4
- Developed by
- ISO / IEC (1997)
- Common bitrates
- 96 / 128 / 192 / 256 kbps
- Typical file size
- ~1 MB per minute at 128 kbps
- Output support
- Convert to MP3, WAV, or M4A
How AAC works
Like MP3, AAC uses psychoacoustic modelling to remove audio information that most listeners don't consciously perceive. AAC improves on MP3 with more advanced compression algorithms, better handling of high frequencies, and support for up to 48 audio channels (versus MP3's 2).
In practical terms, an AAC file at 128 kbps sounds noticeably cleaner than an MP3 at the same bitrate. At 256 kbps, AAC is indistinguishable from the original source for most listeners on most equipment.
AAC vs M4A — what's the difference?
M4A is a container format (an MPEG-4 audio file), and the audio inside it is almost always encoded in AAC. In practice, .aac and .m4a files are technically different things, but they contain the same kind of audio data. Most players handle both interchangeably.
Apple uses .m4a for iTunes purchases and voice memos. Streaming services like Spotify, Apple Music, and YouTube use AAC encoding inside various containers.
Where AAC is supported
AAC has excellent compatibility across modern platforms:
- Apple devices — native support everywhere: iPhone, iPad, Mac, Apple TV, AirPods
- Streaming — Spotify, Apple Music, YouTube, Tidal, and Amazon Music all use AAC
- Browsers — supported in Chrome, Safari, Firefox, and Edge
- Android — full native support since Android 1.0
- Older hardware — some older car stereos and standalone audio players support only MP3. If hardware compatibility is the concern, converting to MP3 is safer.
Strengths and weaknesses
Strengths
- Better quality than MP3 at the same bitrate
- Default format on Apple ecosystem
- Used by all major streaming platforms
- Wide hardware and software support
- Efficient at low bitrates (good for podcasts, voice)
Weaknesses
- Not universally supported by old hardware
- Lossy — original data cannot be recovered
- Some DRM-protected .m4a files cannot be converted
- Slightly higher encoding complexity than MP3
When to convert from AAC
- To MP3 — if you need to play the file on older hardware (car stereos, legacy players) that doesn't support AAC. Expect a minor quality reduction since you're converting one lossy format to another.
- To WAV — if a professional audio application requires uncompressed input. The WAV will not be higher quality than the AAC source, but it will be universally compatible with editing software.
- To M4A — rarely needed; .aac and .m4a are closely related. Some tools handle one extension better than the other.
Frequently asked questions
Is AAC better than MP3?
For equivalent file sizes, yes — AAC delivers better audio quality than MP3 due to more efficient compression. At high bitrates (320 kbps), the practical difference is minimal for most listeners.
Can I convert a DRM-protected AAC file?
No. Files purchased with FairPlay DRM (older iTunes purchases) are encrypted and cannot be converted by any standard converter, including this one. Only DRM-free AAC files can be processed.
Will converting AAC to WAV improve quality?
No. Converting a lossy format to a lossless one creates a larger file but does not restore the audio data that was discarded during AAC encoding. The quality ceiling is set by the original AAC file.
Last updated: January 1, 2025