MP3 vs M4A: which audio format should you use?

MP3 is both a compression method and a file type. It has been the default for digital music since the late 1990s and is supported by virtually every phone, car stereo, speaker, and app.

M4A is an audio-only MPEG-4 file. It usually contains audio compressed with AAC, the successor to MP3, and is the default for Apple Music purchases, iPhone voice memos, and many podcast apps. Some M4A files contain lossless ALAC audio instead, which is much larger.

AAC is more efficient than MP3, so an M4A file usually sounds better than an MP3 of the same bitrate, or matches its quality at a smaller size. The difference is most noticeable at lower bitrates, such as 96–128 kbps, where MP3 can make cymbals and applause sound swishy.

At 256 kbps and above, most listeners cannot tell the two apart on typical headphones or speakers.

MP3 is the safe choice when you don't know where the file will be played: older car stereos, budget MP3 players, some smart TVs, and certain upload forms only accept MP3. M4A plays on all modern phones, computers, and browsers, but older or very basic hardware can fail to recognize it.

Choose M4A when you want the best quality per megabyte and you're using modern devices or Apple software. Choose MP3 when compatibility is the top priority, or when someone has specifically asked for it.

Avoid converting between lossy formats repeatedly. Every lossy encode discards a little more information, so converting an M4A to MP3 and back again leaves you with a file that's worse than either original. Start from the highest-quality source you have.

When you extract audio from a video, the result can only be as good as the soundtrack in that video. A phone recording with background noise will still have background noise. Check the downloaded file's extension and play it on the device you intend to use before deleting the original video.