Manatee

How to convert FLAC to MP3 on a Mac

· 6 min read

The Music app on a Mac will not import FLAC, so its built-in converter is no help here. Use ffmpeg in Terminal (ffmpeg -i track.flac -b:a 320k track.mp3) or drop the files into Manatee and pick MP3 as the target; both run entirely on your Mac and carry the tags across. Keep the original FLAC afterward. It is the lossless master, and the MP3 is a copy made for convenience.

What you are giving up, and why it usually does not matter

FLAC is lossless: it packs the audio the way a ZIP packs a document, and decoding gives back every bit of the original. MP3 is lossy: it throws away the parts of the sound that a psychoacoustic model predicts you will not notice, and that discarded data never comes back.

For a car stereo, a phone, a USB stick for a friend, or a player that simply refuses FLAC, a high bitrate MP3 is the right trade. A 320 kbps MP3 is roughly a third the size of the FLAC, and the difference is very hard to hear on ordinary equipment. The mistake is converting your only copy. Do the conversion, use the MP3 where you need it, and leave the FLAC where it was. The full reasoning is in lossless vs lossy: what happens to audio when you convert it.

Why the Music app cannot do this one

macOS has understood FLAC at the system level since High Sierra: Finder shows the duration, Quick Look plays it with the space bar, and QuickTime Player can open it in recent versions. But the Music app has never supported FLAC import, and its File > Convert menu only works on tracks that are already in the library. Drag a FLAC onto Music and nothing happens.

If you convert a lot of audio and already own an MP3 workflow in Music, the practical trick is a two-step: convert FLAC to something Music accepts (WAV or AIFF, both lossless), import that, then use Music’s Create MP3 Version. That is more steps than either method below, so only bother if you specifically want Music to manage the output.

Option 1: ffmpeg in Terminal

ffmpeg is free, open source, and handles FLAC decoding and MP3 encoding in one pass. With Homebrew installed, brew install ffmpeg sets it up.

  1. Open Terminal (Applications, Utilities).
  2. Type cd with a trailing space, drag the folder containing your FLAC files onto the Terminal window, and press Return. Terminal fills in the path.
  3. Convert one file at a constant 320 kbps:
ffmpeg -i "track.flac" -codec:a libmp3lame -b:a 320k "track.mp3"
  1. Or use variable bitrate, which gives the same perceived quality in a somewhat smaller file. -q:a 0 is the highest VBR setting, -q:a 2 is a widely used balance:
ffmpeg -i "track.flac" -codec:a libmp3lame -q:a 0 "track.mp3"
  1. To convert every FLAC in the folder, run a loop:
for f in *.flac; do ffmpeg -i "$f" -codec:a libmp3lame -b:a 320k "${f%.flac}.mp3"; done

ffmpeg copies the title, artist, album, track number, and other tags by default. Embedded cover art normally survives too, but it is worth checking one file in Finder’s Get Info or in the Music app before you convert a whole collection.

Option 2: Manatee

If a Terminal window is not your idea of a good afternoon, Manatee does the same conversion from a drop zone.

  1. Open Manatee and choose Convert.
  2. Drag the FLAC files into the window, or drag them onto the menu bar icon. A whole album folder is fine; each file becomes a job in the list and you can watch the progress.
  3. Pick MP3 as the target.
  4. The MP3s are written as new files alongside the originals. Manatee never modifies or deletes the source.

The conversion engine inside Manatee is ffmpeg, bundled in the download, so the result is the same quality as the command line route. Nothing is uploaded; the only network call the app ever makes is a license check. It is free for 24 hours with every feature, then $9 once.

What Manatee does not do: it will not edit the audio, normalize volume, or split a single FLAC plus a cue sheet into tracks. If you have one large FLAC of an entire album, split it first with a tool designed for cue sheets, then convert the pieces.

Picking a bitrate

Use Suggested setting
Music you care about, any player 320 kbps constant, or VBR -q:a 0
Phone or car where space matters VBR -q:a 2 (roughly 190 kbps average)
Spoken word, audiobooks, lectures 128 kbps, or 96 kbps mono

Two things people get wrong. First, a higher bitrate cannot add quality that the source lacks, but since FLAC is lossless the source has everything, so 320 kbps is a genuine top-quality MP3. Second, do not convert MP3 to MP3 later to “fix” a bitrate choice; each lossy pass removes more. If you want a different bitrate, go back to the FLAC and convert again.

Tags, cover art, and file names

The MP3 tag standard (ID3) and FLAC’s tag system (Vorbis comments) store roughly the same information, and both ffmpeg and Manatee translate between them. Check a couple of results for the things that most often go astray:

  • Cover art. If it is missing, the picture may have been a separate cover.jpg in the folder rather than embedded. You can add it in the Music app with Get Info.
  • Track numbers. FLAC allows “3/12” style numbering; some old MP3 players only read the first number. Harmless, but good to know.
  • Album artist and compilation flags. These survive, but older car head units ignore them and sort by the track artist instead.

If you are handing the MP3s to someone else and would rather not ship the comments and encoder notes along with them, how to remove metadata from audio files on a Mac covers cleaning them.

Questions

Will the MP3 sound worse than the FLAC? At 320 kbps, on ordinary headphones or speakers, most people cannot tell them apart. On a revealing system with quiet, complex passages you might. That is exactly why the advice is to keep the FLAC and treat the MP3 as a travel copy.

Can I convert MP3 back to FLAC to get the quality back? No. You will get a FLAC file that is larger than the MP3 but contains only what the MP3 contained. Lossy means the discarded data is gone.

The FLAC will not play anywhere, not even Quick Look. Is it the format or the file? Possibly damage, especially if it came from an interrupted download or a failing drive. Run ffmpeg -i track.flac on its own: a format or header error points to a damaged file, and ffmpeg will often still convert whatever is intact before the damage. Corrupted MP3 or M4A won’t play on Mac: how to repair it applies to FLAC as well.

Should I pick M4A (AAC) instead of MP3? If everything you play on is from the last decade, AAC at 256 kbps sounds as good as MP3 at 320 and is a bit smaller. MP3 still wins on compatibility: every player made in the last twenty-five years reads it. Both are targets in Manatee, and ffmpeg handles both.