M4A

M4A, short for MPEG-4 Audio, is a digital audio file format that uses the MPEG-4 Part 14 container (the ISO base media file format) to store audio data. The common file extension is .m4a, and the format is designed for audio-only files within the MP4 family. While .mp4 is associated with video, .m4a is used when the file contains only audio tracks.

The most common codec inside M4A is AAC (Advanced Audio Coding), which offers high-quality sound at relatively small file sizes. A lossless option, Apple Lossless Audio Codec (ALAC), is also used in M4A files for those who want exact audio reproduction without compression loss. Although M4A can carry other codecs, AAC and ALAC are the principal ones in everyday use. M4A files are typically unprotected, but historically Apple’s iTunes catalog has included DRM-protected variants under different extensions.

M4A files are widely supported across operating systems and media players, including Apple’s iTunes and QuickTime, as well as many third-party players on Windows, macOS, Linux, and mobile platforms. They can carry rich metadata, such as artist, album, artwork, and track information, using standard MP4 tagging schemes.

Compared with MP3, M4A with AAC generally delivers better quality at similar or lower bitrates, though MP3 remains universally compatible in some contexts. M4A is distinct from the video-oriented MP4 container, but the underlying structure is shared, allowing flexible streaming and storage of high-quality audio.