Everything you need to know about FLAC
FLAC (Free Lossless Audio Codec, .flac) is the dominant open-source lossless audio format, created by Xiph.org in 2001. It compresses CD-quality audio to ~50-60% of WAV size while preserving every single sample - bit-for-bit identical to the original. Audiophiles and music collectors use FLAC for archival.
How it works under the hood
- Linear prediction. FLAC uses a polynomial model to predict each sample, then encodes the residual (difference) with Rice coding. Cleaner math than MP3's psychoacoustic gymnastics.
- No quality settings. Compression levels (0-8) trade encoding speed for compression ratio. The output is byte-identical lossless either way - higher levels just spend more CPU finding tighter compression.
- Native metadata. Uses Vorbis comment for tags plus dedicated blocks for cuesheet, application data, and embedded album art. Best metadata story of any audio format.
- Streamable. Each FLAC frame is independent, making seeking instant. The format also supports replay gain natively.
Where you'll actually use it
- High-resolution music collections (Bandcamp, Qobuz, Tidal)
- Audio archival and library digitization
- Hi-fi audiophile playback through dedicated DACs
- Master backups before lossy distribution encoding
How it compares to alternatives
FLAC vs WAV: Same audio quality, FLAC is ~50% smaller and has better metadata. FLAC vs ALAC: Both lossless, FLAC is more widely supported outside Apple. FLAC vs MP3 320: Both hard to distinguish in blind tests, but FLAC is provably lossless - MP3 isn't.
Things that will trip you up
- iTunes and iOS don't natively play FLAC (use ALAC instead for Apple ecosystem)
- Phones with low-quality DACs won't reveal FLAC's quality advantage over 320kbps MP3
- FLAC files at 24-bit/192kHz are huge (~120 MB per album) - 16-bit/44.1kHz is plenty for most purposes
Test it yourself: foobar2000, VLC, Audacity all play FLAC natively. `flac` and `metaflac` are the official command-line tools. `flac --decode` converts to WAV.