What is a .m4a file?

Every voice memo you've recorded on an iPhone, every iTunes purchase, every Apple Music download, every GarageBand export — they're all M4A files. The format is Apple's way of saying "this is audio, not video" to an MP4 container. Under the hood, M4A and MP4 are the same thing; the different extension just tells your OS to open it in a music player instead of a video player.

M4A typically contains AAC-encoded audio, which sounds better than MP3 at the same bitrate. Some M4A files contain Apple Lossless (ALAC) audio instead, which is Apple's answer to FLAC — bit-perfect quality at smaller file sizes. The container supports metadata, album art, and chapter markers. Support is universal on Apple devices and very good everywhere else, though some older car stereos and portable players still only speak MP3.

Apple Music, iTunes, and VLC all play M4A natively. Windows Media Player handles most M4A files. If you need to share audio with someone on an older device or a system that only accepts MP3, convert with fwip — the quality difference at high bitrates is negligible.