Compress M4A Files

An M4A file is an MPEG-4 Part 14 container. Inside, the audio is usually encoded as AAC (lossy, like MP3 but better). Sometimes it's ALAC (Apple Lossless, like FLAC). Both produce .m4a files. iTunes voice memos, Apple Music downloads, and most YouTube audio extracts are AAC inside M4A. Apple Music Lossless tracks are ALAC inside M4A.

This tool re-encodes the audio at the bitrate you pick using the AAC encoder. If your M4A is ALAC, the re-encode converts it to AAC (which is lossy). For lossless ALAC handling, use the [M4A to FLAC](/m4a-to-flac) or [M4A to WAV](/m4a-to-wav) tools instead.

Apple Voice Memos exports as M4A AAC, typically at 64 kbps for voice. Re-compressing to a lower bitrate isn't usually meaningful — voice at 64 kbps is already efficiently compressed. The actual ask is usually one of: convert to MP3 for sharing with non-Apple users (use [M4A to MP3](/m4a-to-mp3)), or extract just the audio from a M4A in higher quality (skip compression and convert to WAV).

If you're hitting attachment limits sharing voice memos, the right move is splitting the file rather than re-compressing. Most voice memo files are already compact — a 30-minute recording at 64 kbps is about 14 MB.

AAC is the modern successor to MP3. At the same bitrate, AAC produces noticeably better quality — typically 25–30% more efficient. A 96 kbps AAC file is comparable to a 128 kbps MP3 in audible quality. This means you can compress more aggressively in M4A than in MP3 without quality loss. Combined with universal Apple ecosystem support and broad Android support, M4A AAC is the right choice when you control playback environment.

The trade-off: M4A has marginally less universal support than MP3 in legacy software (some old hardware MP3 players, older car stereos). For maximum compatibility, MP3 still wins. For best quality at given size, AAC wins.