What you should know
M4A is an MP4 container dedicated to audio, popularised by iTunes. It usually carries AAC and differs from a raw .aac file by its complete metadata: title, artist, cover art, chapters.
It is the default format for iTunes purchases and iPhone recordings. It is also lossless when it carries ALAC, Apple's counterpart to FLAC.
Strengths
- Rich metadata and embedded cover art
- AAC quality at reduced bitrate
- Native playback on iOS, macOS and most recent players
- Can carry lossless audio (ALAC)
Limitations to know
- Less universal than MP3 on old devices
- Often confused with raw AAC, which complicates conversions
- The ALAC codec is less well supported than FLAC
- Some players display M4A metadata poorly
When to use it
Keep M4A within the Apple ecosystem and for libraries with covers and metadata. For an old device or a recipient whose equipment you do not know, MP3 is safer.
Quality, size and compatibility
An M4A in AAC is a lossy format: do not re-encode it needlessly. If it carries ALAC, converting to FLAC preserves the whole signal; the reverse works too.
Frequently asked questions
- M4A vs MP3: what is the difference?
- M4A generally carries AAC, which is more efficient at equal bitrate, with better metadata. MP3 remains more widely read by old hardware.
- Can M4A be converted to MP3 without losing quality?
- No: it is a re-encode from one lossy format to another. Choose a high bitrate (320 kbps) to limit degradation, or convert from the uncompressed source if you still have it.