Lossless Audio: Why Format Still Matters
When you choose a lossless audio format, you're guaranteed that every bit of the original recording is preserved — but the format you choose still affects compression efficiency, software compatibility, metadata support, and long-term archival suitability. FLAC and ALAC are the two dominant lossless formats for consumer audio, and understanding their differences helps you pick the right one for your workflow.
What Is FLAC?
FLAC (Free Lossless Audio Codec) is an open-source, royalty-free lossless audio codec developed by the Xiph.Org Foundation, first released in 2001. It is the most widely supported lossless format across non-Apple platforms and is the de facto standard for audiophile music distribution.
- License: BSD (open source, royalty-free)
- Container: Native FLAC container or Ogg
- File extension: .flac
- Max bit depth: 32-bit
- Max sample rate: 655,350 Hz
- Max channels: 8
What Is ALAC?
ALAC (Apple Lossless Audio Codec) was developed by Apple and originally released in 2004 as a proprietary format. Apple open-sourced it in 2011, but it remains most at home in the Apple ecosystem. ALAC files are stored inside the MP4 container, the same container used for AAC audio and video.
- License: Apache 2.0 (open source since 2011)
- Container: MP4 / M4A
- File extension: .m4a (also .alac on some systems)
- Max bit depth: 32-bit
- Max sample rate: 384,000 Hz
- Max channels: 8
Compression Efficiency
Both formats compress losslessly, but FLAC generally achieves slightly better compression ratios — meaning smaller file sizes for equivalent audio content. In practice, both formats typically reduce a PCM WAV file to roughly 50–70% of its original size, depending on the audio complexity. The difference between FLAC and ALAC file sizes for the same source material is usually small enough to be practically insignificant.
Compatibility Comparison
| Platform / Software | FLAC | ALAC |
|---|---|---|
| macOS | Via third-party (VLC, etc.) | Native (iTunes/Music app) |
| iOS | iOS 11+ native support | Native |
| Windows | Native (Windows 10+) | Via iTunes or third-party |
| Android | Native on most devices | Limited native support |
| Linux | Excellent native support | Via FFmpeg / VLC |
| VLC, Foobar2000, Kodi | Full support | Full support |
| Apple Music | Not supported for upload | Native streaming format |
| Plex, Jellyfin | Full support | Full support |
Metadata and Tagging
FLAC uses Vorbis comment tags — a flexible, plain-text tagging system with no field limitations. You can add standard fields (TITLE, ARTIST, ALBUM, DATE) or any custom fields you like. FLAC also natively supports embedded album artwork.
ALAC, being stored in an MP4 container, uses iTunes-compatible MP4 metadata tags. These are well-supported by Apple software and compatible with tools that understand MP4 metadata, but the tag naming conventions differ from Vorbis comments, which can cause minor issues when moving between ecosystems.
Archival Considerations
For long-term archival purposes, FLAC has some advantages:
- Open standard: FLAC's specification is fully open and freely available, ensuring future decodability
- Built-in checksums: FLAC supports MD5 checksums embedded in the file for integrity verification
- Widely adopted: Large audiophile communities, online music stores, and archival institutions default to FLAC
ALAC is also open-source now, but its dependency on the MP4 container adds a layer of complexity that FLAC avoids.
Which Should You Choose?
Choose FLAC if:
- You use Windows, Linux, or Android as your primary platform
- You want maximum software compatibility and open-standard guarantees
- You're building a long-term audio archive
- You purchase or download music from audiophile stores (most use FLAC)
Choose ALAC if:
- You're fully embedded in the Apple ecosystem (Mac, iPhone, iPad, Apple TV)
- You want lossless audio that syncs natively through iTunes or the Music app
- You need to store lossless audio inside an MP4 container alongside video
Converting Between Them
Converting between FLAC and ALAC is lossless — no audio quality is lost because both are lossless representations of the same PCM data. FFmpeg handles the conversion cleanly:
# FLAC to ALAC
ffmpeg -i input.flac -codec:a alac output.m4a
# ALAC to FLAC
ffmpeg -i input.m4a -codec:a flac output.flacThis means you don't need to make a permanent commitment to one format — you can always convert without penalty if your needs change.