FLAC to ALAC: Converting Lossless Audio for Apple Devices and Apple Music

The Apple Lossless Problem

You've built a lossless audio library in FLAC format — probably because it's the open, universally supported format for archiving and playing high-quality audio. FLAC players exist on every platform: Android, Windows, Linux, web. But then you want to use that library on an iPhone, add albums to Apple Music, or sync tracks to your Mac's native music app.

Problem: Apple devices don't natively play FLAC.

This isn't a codec capability issue — Apple devices are perfectly capable of decoding FLAC. Apple simply chose not to support it, presumably to push ALAC (Apple Lossless Audio Codec), their own proprietary — now open-source — lossless format. iPhones, iPads, Macs, and Apple Music all play ALAC natively, but FLAC files require third-party apps.

The good news: FLAC to ALAC conversion is 100% lossless. Both formats are bit-for-bit perfect representations of the original PCM audio. Converting between them produces an ALAC file that is mathematically identical to the source FLAC — no audio quality is lost. You're just changing the container and compression algorithm, not the underlying audio data.

FLAC vs ALAC: What's Actually Different

Understanding the technical difference helps you choose when conversion is worthwhile:

Both formats are lossless, meaning both are bit-for-bit copies of the original PCM audio data. An ALAC file is typically 5–10% larger than the equivalent FLAC due to compression algorithm differences, but both play identically.

For a detailed technical comparison, see our ALAC vs FLAC comparison guide.

Converting FLAC to ALAC with FFmpeg (Command Line)

FFmpeg is the most reliable tool for FLAC to ALAC conversion — it handles metadata, artwork, and multi-channel audio correctly:

# Convert single FLAC file to ALAC (.m4a)
ffmpeg -i input.flac -c:a alac output.m4a

# Convert and preserve all metadata and artwork
ffmpeg -i input.flac -c:a alac -c:v copy output.m4a

# Batch convert all FLAC files in a directory
for f in *.flac; do
  ffmpeg -i "$f" -c:a alac -c:v copy "${f%.flac}.m4a"
done

# Convert while renaming output with .alac extension (some players prefer this)
ffmpeg -i input.flac -c:a alac output.alac

# Verify the conversion is lossless (compare checksums)
ffmpeg -i input.flac -c:a pcm_s32le /tmp/original.wav
ffmpeg -i output.m4a -c:a pcm_s32le /tmp/converted.wav
md5sum /tmp/original.wav /tmp/converted.wav
# Both checksums should be identical for a lossless conversion

The -c:a alac flag tells FFmpeg to encode audio using the ALAC codec. The -c:v copy flag copies the album artwork (stored as a video stream in FLAC containers) without re-encoding.

Converting FLAC to ALAC with iTunes / Music App (macOS)

If you prefer a GUI and are already on macOS, Apple's Music app can convert FLAC to ALAC:

1. Open Music (macOS Catalina or later) or iTunes (older macOS)
2. Go to Music → Settings → Files (macOS) or Edit → Preferences → Import Settings (iTunes)
3. Set "Import Using" to Apple Lossless Encoder
4. Close settings
5. Go to File → Convert → Create Apple Lossless Version
6. Select the FLAC file(s) to convert

Wait — there's a catch. The Music app on macOS doesn't actually support importing FLAC files natively for conversion. You need a third-party step:

Path 1 (simplest): Convert FLAC → ALAC with FFmpeg, then import the .m4a files into Apple Music.

Path 2: Use XLD (X Lossless Decoder), the gold-standard macOS audio converter for lossless formats. It converts FLAC to ALAC with full metadata preservation and batch support.

Converting for iPhone Sync

To get ALAC files onto an iPhone:

1. Convert FLAC to ALAC using FFmpeg or an online audio converter
2. Open Apple Music on your Mac
3. Drag the .m4a files into your Music library
4. Connect your iPhone
5. In the sidebar, select your iPhone
6. Under "Music" settings, enable sync for the albums/playlists you want
7. Sync

Alternatively, if you use iCloud Music Library (requires an Apple Music subscription or iTunes Match), adding ALAC files to your Mac library makes them available on all your Apple devices without a wired sync.

Batch Converting an Entire FLAC Library

For large music libraries, a bash script handles batch conversion with organization:

#!/bin/bash
# Batch FLAC to ALAC conversion, preserving directory structure
INPUT_DIR="$HOME/Music/FLAC"
OUTPUT_DIR="$HOME/Music/ALAC"

find "$INPUT_DIR" -name "*.flac" | while read -r file; do
  # Determine output path (same structure, different root)
  relative_path="${file#$INPUT_DIR/}"
  output_file="$OUTPUT_DIR/${relative_path%.flac}.m4a"
  output_dir=$(dirname "$output_file")

  # Create output directory if needed
  mkdir -p "$output_dir"

  # Skip if already converted
  if [ -f "$output_file" ]; then
    echo "Skipping (exists): $relative_path"
    continue
  fi

  # Convert
  ffmpeg -i "$file" -c:a alac -c:v copy "$output_file" -loglevel quiet

  if [ $? -eq 0 ]; then
    echo "Converted: $relative_path"
  else
    echo "FAILED: $relative_path"
  fi
done

echo "Conversion complete."

This script converts your entire FLAC library to ALAC while preserving the Artist/Album/Track directory structure. It skips files already converted (useful for incremental conversions when you add new FLAC albums).

Handling Sample Rates and Bit Depth

High-resolution FLAC files (96 kHz/24-bit, 192 kHz/24-bit) convert to ALAC without any degradation. ALAC supports up to 384 kHz and 32-bit, so any FLAC file fits within ALAC's specification:

# Convert high-res FLAC (e.g., 96kHz/24-bit) to ALAC
ffmpeg -i hi-res-96khz-24bit.flac -c:a alac hi-res-96khz-24bit.m4a

# Verify preserved sample rate and bit depth
ffprobe -v quiet -print_format json -show_streams hi-res-96khz-24bit.m4a | \
  python3 -c "import json,sys; s=json.load(sys.stdin)['streams'][0]; print(f\"{s['sample_rate']}Hz / {s['bits_per_raw_sample']}-bit\")"

Apple Music on iPhone supports up to 48 kHz / 24-bit for local ALAC playback. Files above 48 kHz will play but may be downsampled by the device's audio stack depending on hardware. Mac and iPad support higher sample rates via Core Audio.

What About FLAC on iPhone Without Converting?

If you want to avoid conversion entirely, several third-party iOS apps play FLAC natively:

• VLC for iOS — Free, plays FLAC from Files app or local network
• Foobar2000 — Free, specifically designed for audiophiles
• VOX Music Player — Has cloud sync features for FLAC libraries
• Neutron Music Player — Audiophile-focused with DSP features

The trade-off: these apps don't integrate with Apple Music, Siri, CarPlay, or AirPlay as seamlessly as native formats do. For a seamlessly integrated Apple ecosystem experience, ALAC is the right format.

Metadata Considerations

FLAC and ALAC use different metadata systems. FLAC uses Vorbis Comment tags (free-form key=value pairs). ALAC uses iTunes-style atoms (a structured set of predefined fields).

Common mapping:

FFmpeg handles this mapping automatically during conversion. Obscure or non-standard Vorbis Comment fields may not transfer — check your converted files in a tag editor like MusicBrainz Picard or Mp3tag if metadata completeness matters.

File Size Expectations

ALAC files are typically 5–15% larger than equivalent FLAC files. For a 500-album library:

The size increase is predictable and manageable. If you're keeping both formats (FLAC for cross-platform, ALAC for Apple ecosystem), budget for approximately double storage.

For more context on lossless audio trade-offs, see our FLAC vs MP3 guide and the best audio format for music guide.

Frequently Asked Questions

Is FLAC to ALAC truly lossless? Will I hear any difference?

Yes, completely lossless. Both formats are bit-for-bit perfect representations of the original PCM audio. You can verify this mathematically — decode both to WAV and compare MD5 checksums. They will be identical. No listening test can distinguish them because they contain the same audio data.

Can I convert back from ALAC to FLAC with no quality loss?

Yes. ALAC → FLAC is also lossless. You can convert in both directions indefinitely with no audio degradation — it's just changing the container/compression algorithm, never altering the audio samples themselves.

My ALAC files show the wrong sample rate in Music app. What happened?

Usually a metadata issue, not an actual sample rate problem. Use ffprobe -v quiet -show_streams file.m4a to check the actual sample rate in the file. If correct, the Music app may have cached incorrect metadata — remove and re-add the file.

Why doesn't Apple support FLAC natively?

Apple added FLAC support to various frameworks in 2021 (iOS 15, macOS 12), but the Music app's support remains inconsistent. Apple's ecosystem promotion of ALAC (which is now open-source under Apache 2.0) is likely a factor. VLC and third-party players handle FLAC reliably on Apple devices.

Can I use AirDrop to transfer ALAC files to iPhone?

Yes. AirDrop sends any file format. The ALAC .m4a file will land in the Files app; you can then open it in the Music app or a third-party player.

Conclusion

FLAC to ALAC conversion is one of the few format conversions where you genuinely lose nothing — the audio quality is mathematically identical. The only cost is slightly larger files (5–15%) and conversion time.

For single-album conversions, the audio converter gets the job done without installing any software. For full library conversions, the FFmpeg batch script above is the most efficient path.

Once your library is in ALAC format, it integrates seamlessly with every Apple product — iPhone, iPad, Mac, HomePod, CarPlay, Apple Music, and AirPlay. For cross-platform access (Android, Windows), keep your FLAC originals as the master archive.