Convexy

Convert FLAC to M4A on iPhone

iOS can play a FLAC, but the Music app will not take one into your library. Converting to M4A is the way in — a clean, first-generation AAC encode from a lossless master.

The actual problem you are solving

This is worth being precise about, because the internet is confused about it. iOS can decode FLAC. Put one in the Files app, tap it, and it plays. Playback is not the issue.

The issue is the Music app library, which does not accept FLAC. If you want your tracks sitting alongside everything else — searchable, in playlists, on your Watch, on CarPlay, with artwork — they need to be in a format Apple's library ingests. AAC in an M4A container is the obvious one.

So converting is not a workaround for a codec Apple cannot handle. It is a workaround for a library policy. That distinction matters, because it tells you when you actually need to convert (getting music into the library) and when you do not (simply listening to a file you have).

This is a first-generation encode

FLAC is lossless. It decodes back to the exact samples that went into it, bit for bit — it is compressed the way a ZIP is compressed, not the way an MP3 is.

AAC, the codec inside the M4A, is lossy. It permanently discards audio it judges you will not miss. There is no version of this conversion that avoids that, and any app claiming otherwise is wrong.

What makes it a good lossy conversion is that the encoder is working from a genuine master. Nothing was thrown away before it arrived, so it makes its decisions once, with complete information. This is the best AAC that recording can produce — categorically different from transcoding an MP3 or an existing M4A, where a second encoder piles new damage on old.

Your FLAC is untouched. Convexy writes a new file; the original stays exactly where it is. Archive the FLAC, carry the M4A, and re-encode from the master any time you want a different format or a different target. That is the whole reason to keep a lossless library in the first place.

What about Apple Lossless?

The obvious question: Apple has its own lossless codec, ALAC, and the Music app does accept it. FLAC to ALAC would be a lossless-to-lossless conversion with no quality cost at all, and for an archival library that is the theoretically correct move.

Convexy does not produce ALAC. It writes AAC into the M4A container. If bit-exact lossless inside the Apple ecosystem is what you need, Convexy is not the tool for that particular job, and we would rather tell you than let you find out after paying.

For most people, most of the time, a first-generation AAC from a lossless master is the right answer anyway: it is a fraction of the size, it plays on everything Apple makes, and the master is still safe on disk. But if you specifically want lossless in your library, know that this conversion is not it.

What Convexy writes

Convexy decodes the FLAC and encodes AAC with Apple's own exporter, on the device, at its standard high-quality setting. There is no bitrate dial for M4A — Apple's exporter does not expose one.

If you need a specific bitrate (a submission form, a podcast host, a storage budget), convert to MP3 instead: Convexy offers 128, 192, 256 and 320 kbps there, along with sample rate and channel controls. From a lossless FLAC, a 320 kbps MP3 is also a first-generation encode and an entirely respectable file.

High-resolution FLAC

If your FLAC is 24-bit / 96 kHz, understand that AAC cannot carry that. It is a lossy, perceptually-coded format and the extra depth and bandwidth have nowhere to go. The M4A will be a good-sounding, ordinary-resolution file.

That is not Convexy discarding your hi-res audio out of carelessness — it is the destination format's ceiling. Keep the FLAC as the master it was bought to be, and treat the M4A as the copy you actually listen to on a phone, in a car, on the train.

How to do it

  1. Bring the FLAC into Convexy

    Tap Browse files and pick it from Files or iCloud Drive, or share it in from wherever your library lives.

  2. Choose M4A

    Convexy shows only what a FLAC can actually become — M4A, MP3, WAV, AIFF and CAF.

  3. Convert

    Apple's AAC encoder runs on your iPhone. Nothing is uploaded, and the original FLAC is left untouched.

  4. Save or share it

    Save the M4A to Files, or share it straight into the Music app or wherever you keep your listening copies.

  5. Convert a batch if you have a library

    Select several FLACs at once when browsing and Convexy converts them as a batch, with per-file status and retry.

Common questions

Can my iPhone play FLAC without converting?

Yes. iOS decodes FLAC natively — a FLAC in the Files app plays when you tap it. What it will not do is accept FLAC into the Music app library. If you only want to listen to a file you already have, you do not need to convert anything.

Does FLAC to M4A lose quality?

Yes. AAC is lossy and permanently discards audio. But because FLAC is a lossless master, this is a single, first-generation encode — the best AAC that recording can yield. Keep the FLAC and the loss costs you nothing you cannot regenerate.

Can Convexy convert FLAC to ALAC (Apple Lossless)?

No. Convexy writes AAC into the M4A container, not ALAC. If you specifically need bit-exact lossless inside the Apple Music library, this conversion will not give you that, and you will want a different tool. We would rather say so plainly than let you discover it afterwards.

Will I hear the difference between the FLAC and the M4A?

On a phone, in a car, on headphones on a train — almost certainly not. On a good system, in a quiet room, with material you know intimately, possibly. This is why the correct pattern is to archive the lossless master and carry the lossy copy: you never have to make the choice permanently.

Can I convert a whole FLAC library at once?

Yes — select multiple files when browsing and Convexy runs them as a batch, showing per-file status and letting you retry any that fail. Everything runs on the device, so a large library is limited only by your phone's patience, not by an upload queue.