Lossless compression, not lossy reduction
The crucial word is lossless. Where MP3 or AAC throw away audio they judge inaudible to shrink the file, FLAC uses prediction and entropy coding to pack the same samples more efficiently — and decode them back to exactly what went in. Run a checksum on the decoded output and it matches the original WAV byte for byte. The compression ratio depends on the music, but halving the size of a CD rip is typical, so you keep full quality at a fraction of WAV’s footprint. Decoding is light enough for phones and cheap players, and the format includes built-in error detection so corruption is caught rather than silently played.
Open, tagged and built to last
FLAC is royalty-free and its reference implementation is open source, which is a large part of why it became the community standard for archiving music. Unlike WAV, it has a proper, well-supported tagging system: artist, album, track numbers, lyrics and embedded cover art all travel inside the file and are read consistently across players. That combination — perfect fidelity, sensible size and reliable metadata — is exactly what a long-term library needs. The historical catch was Apple: for years iTunes and the stock iOS players did not handle FLAC, pushing Apple users toward ALAC instead, though support has since broadened across apps and platforms.
Strengths
- Truly lossless — decoded audio is identical to the source.
- Roughly half the size of uncompressed WAV.
- Open, royalty-free and widely implemented.
- Rich, reliable tagging with embedded artwork.
Limitations
- Far larger than lossy MP3, AAC or Opus.
- Historically poor support on default Apple players.
- Overkill for casual listening on small portable devices.
- Not accepted by some streaming and upload services.
When to use FLAC
Use FLAC to rip CDs, archive masters and build a library you want to keep at full quality without WAV-sized files; pick a lossy format instead when storage or bandwidth is tight.
FLAC FAQ
- Is FLAC better than MP3?
- For quality, yes — FLAC keeps every sample while MP3 discards some permanently. The cost is size: FLAC files are several times larger, so MP3 still wins where space or bandwidth matters most.
- Can I tell FLAC and MP3 apart by ear?
- On modest gear at a high MP3 bitrate, most people cannot. FLAC’s real advantage is archival: you can re-encode from it to any future format without compounding loss.
- Will FLAC play on my iPhone?
- Modern iOS handles FLAC in the Files app and many third-party players, though older or stock Apple setups historically did not. If a device refuses it, converting to ALAC or AAC is the usual fix.