Manatee

How to convert a FLAC to M4A on a Mac

· 6 min read

FLAC is a lossless audio format that the Music app and most Apple devices will not play. M4A is the format they do play, so converting is the usual fix. The result is a new file next to the original, and you should keep the FLAC, because the conversion can cost some audio detail depending on how it is encoded.

Why a FLAC will not play in Music

FLAC is an open format that Apple has never built into its own players. Double-click one and QuickLook may show a waveform in some versions of macOS, but Music will refuse to import it, and an iPhone synced from your library will not carry it. The audio itself is fine. The problem is only the wrapper and the codec Apple’s software understands.

M4A is an MP4-style container, and Apple’s apps read it everywhere: Music, QuickTime Player, iPhone, iPad, CarPlay, and Apple TV. That is the reason people convert, and it is a good enough reason on its own.

Know what you are giving up first

There are two kinds of M4A, and they behave differently.

  • Lossy M4A (AAC). This is the common kind. The file is a fraction of the FLAC’s size, and it is made by discarding detail the encoder judges you will not hear. Most listeners cannot tell at a decent bitrate on ordinary headphones, but it cannot be reversed.
  • Lossless M4A (Apple Lossless). This keeps everything the FLAC held, at a size similar to the FLAC. It is the right choice if you want the Apple-friendly wrapper and no loss.

If you are converting a few albums to listen to on a phone, lossy is sensible. If you are building an archive, keep the FLAC files and treat the M4A copies as disposable listening copies. Lossless vs lossy: what happens to audio when you convert it goes into what the choice means in practice.

One rule saves regret: never convert a lossy file back up and expect it to improve. Turning an MP3 into FLAC and then into M4A only stacks losses.

Option 1: Convert with Manatee

Manatee accepts FLAC and writes M4A. It bundles its own copy of ffmpeg, so there is nothing to install, and it works on the Mac with nothing uploaded.

  1. Open Manatee and choose Convert.
  2. Drop your FLAC files into the window, or onto the menu bar icon. You can drop a whole album at once.
  3. Pick M4A as the target.
  4. Each converted file appears next to its FLAC. The original is never modified.

Afterward, select one result in Finder and press Command-I. Under More Info you can see the audio details, which is how you confirm what you ended up with. Manatee is free for 24 hours with every feature, then $9 once. It is not a tag editor, so if the album art or track numbers matter, check them in Music after importing.

Option 2: Use the Terminal if you have ffmpeg

If ffmpeg is already installed, one command does a single file. For lossy AAC:

ffmpeg -i song.flac -c:a aac -b:a 256k song.m4a

For lossless Apple Lossless inside an M4A:

ffmpeg -i song.flac -c:a alac song.m4a

The -b:a 256k sets the bitrate; higher means a bigger file and less loss. To do a whole folder, a short loop works in zsh:

for f in *.flac; do ffmpeg -i "$f" -c:a aac -b:a 256k "${f%.flac}.m4a"; done

This is fast and flexible, but it leaves you to manage the names and any files that fail.

Option 3: Skip the conversion by playing the FLAC another way

If you only want to listen on the Mac, you may not need to convert at all. Any media player that understands FLAC will play the files directly, and they sit in your music folder unchanged. The conversion matters when you need the song inside Music, on an iPhone, or in a car system that reads only Apple formats.

For the Music route specifically, how to add FLAC files to the Music app on a Mac walks through it.

Checking the result

After a batch, spot check before you delete anything.

  1. Play the start, the middle, and the end of one track. A file that cuts off or skips points to a problem with the source.
  2. Compare the file sizes. A lossy M4A is far smaller than its FLAC; a lossless one is not.
  3. Import one file into Music and confirm the title and artist appear. If they do not, the original tags may not have carried across, and you can fill them in with Command-I in Music.

If a track sounds too fast or high-pitched, the cause is usually the sample rate and not the conversion; an audio file that plays too fast or sounds high-pitched explains it.

Questions

Will converting FLAC to M4A reduce the quality? If the M4A is lossy, yes, a little detail is discarded, and you cannot get it back. If it is a lossless M4A, no. Either way, keep the FLAC as your master copy.

Does the FLAC get deleted? No. The converted M4A is a new file beside it, and the FLAC stays exactly as it was.

Can I convert a whole album at once? Yes. Drop all the files into Manatee together and each one is converted in turn, with progress shown in the job list.