Manatee

How to convert Apple Lossless (ALAC) to FLAC on a Mac

· 6 min read

Apple Lossless (ALAC) and FLAC are both lossless formats, so converting from one to the other changes the wrapper and the compression scheme but leaves the audio itself bit-for-bit identical. There is no quality to lose. The real traps are converting files that were never lossless to begin with, and losing track of your tags along the way.

Why you might need FLAC

ALAC is Apple’s lossless format, and it lives in files ending in .m4a. Apple’s apps and devices play it natively. Outside that world, support is patchier: some network music players, car stereos, portable music players, and apps on other platforms read FLAC and ignore ALAC, or handle it badly. FLAC is the lossless format with the widest support outside Apple’s own hardware and software.

What you should not expect is a change in size. Both formats compress the same audio without discarding anything, so the FLAC files will be in the same ballpark as the ALAC ones.

First, check that your .m4a files are actually ALAC

This is the step people skip. The .m4a extension is shared by two very different things: ALAC, which is lossless, and AAC, which is lossy. Converting an AAC file to FLAC gives you a much bigger file with exactly the same audio quality, because FLAC can only preserve what is already there.

Three ways to check:

  1. In the Finder. Select a file, press Command-I, open More Info, and look at Codecs. “Apple Lossless” is what you want. “AAC” means the file is lossy.
  2. In the Music app. Choose View > Show View Options and turn on the Kind column. Lossless tracks show as “Apple Lossless audio file”; lossy ones show some variety of AAC.
  3. In Terminal, for a definite answer, run afinfo on the file:
afinfo ~/Music/album/01-track.m4a

Look at the “Data format” line. alac means Apple Lossless and aac means AAC. The same line shows the sample rate and, for ALAC files, the bit depth of the source, which matters if you have high-resolution albums.

One more thing to know before you start. Songs downloaded from an Apple Music subscription are protected, even when you have lossless playback turned on, and no legitimate tool will convert them. Everything here applies to files you own outright: CDs you ripped in Apple Lossless, lossless purchases from stores that sell them, and your own recordings.

What macOS can and cannot do by itself

macOS plays FLAC without help: QuickTime Player opens it, and Quick Look previews it. But there is no FLAC option anywhere in the export or import settings of Music or QuickTime Player. Music’s import encoders, for example, are AAC, AIFF, Apple Lossless, MP3 and WAV.

That leaves you with a converter. The choice between converters matters less than usual here, because a correct conversion between two lossless formats always produces the same audio. What differs is where the work happens, how comfortably it handles a large batch, and how it treats the originals.

Converting ALAC to FLAC with Manatee

Manatee takes .m4a files and writes FLAC directly.

  1. Copy the albums you want to convert into a working folder outside your Music library, for example on the Desktop. (The reason is below.)
  2. Open the folder, select the tracks (Command-A selects everything), and drag them onto Manatee’s menu bar icon or into its window.
  3. Choose Convert, then FLAC.
  4. The FLAC files appear next to the .m4a originals, which are not modified.

Why the working folder: Manatee writes each new file alongside its original. If you convert inside the Music app’s media folder, the FLAC files end up scattered among files the Music app manages, which is untidy, and Music will not list them anyway. Converting a copy keeps your library exactly as it was.

Everything runs on your Mac with nothing uploaded, and a batch works through unattended, so a whole collection can go in at once. Every feature is free for the first 24 hours, then it is $9 once.

Check the results before you delete anything

A lossless conversion means identical audio, but a few details are worth confirming on a handful of files before you trust the whole batch:

  • Duration. Open a converted track in QuickTime Player and compare its length with the original.
  • Sample rate and bit depth. Run afinfo on the FLAC; the numbers should match the source. A 24-bit, 96 kHz album should still be 24-bit, 96 kHz.
  • Tags and artwork. Open the files in the player or on the device you are moving to, and check that titles, track numbers and cover art came through the way you expect. Tag conventions differ between the two formats, and this is where conversions most often need a touch-up.

Keep the ALAC originals until you have played the FLAC files on the device that needed them. Disk space is cheaper than ripping a CD collection a second time.

Should you convert your whole library?

Only if a device or app you actually use needs FLAC. ALAC is not inferior: it is lossless too, Apple published it as open source years ago, and it fits into Apple’s apps in ways FLAC does not.

A sensible approach for many people is to keep the library in ALAC for Apple devices and convert copies to FLAC for whatever wants them. If you also need lossy copies for a phone with limited storage, make those from the lossless files, never from other lossy ones. Lossless vs lossy explains why, and how to convert FLAC to MP3 on a Mac covers that step. If some of your lossless audio is in WAV rather than ALAC, how to convert a WAV to FLAC works the same way.

Questions

Does converting ALAC to FLAC lose any quality? No. Both formats are lossless, and the decoded audio from the FLAC is identical to the decoded audio from the ALAC.

Can I convert back from FLAC to ALAC later? Yes. Lossless to lossless can go back and forth as often as you like without any change to the audio.

Will the FLAC files be smaller? Usually about the same size, give or take a little. Neither format has much room to beat the other, since both keep every bit of the audio.

Why will some of my .m4a files not convert? If they came from an Apple Music subscription, they are protected downloads rather than files you own outright, and they cannot be converted. Check the Kind column in Music to see where each one came from.