FLAC is an open, royalty-free format for lossless audio. Released in 2001 and maintained by the Xiph.Org Foundation, it compresses audio without discarding anything: decode a FLAC file and you get back exactly the original samples, bit for bit. It is the standard format for ripping CDs, archiving music and buying high-resolution downloads.
How lossless compression works
FLAC predicts each audio sample from the ones before it and stores only the small difference between the prediction and the real value. Those differences take far fewer bits than full samples. The saving depends on the music: quiet, simple recordings compress more than dense, loud ones. Typically a FLAC file is 50–70% the size of the equivalent WAV.
High-resolution FLAC
FLAC supports bit depths up to 32-bit and very high sample rates, so it is also used for “hi-res” music at 24-bit and 96 or 192 kHz. These files can be four to six times larger than CD-quality FLAC.
What FLAC is good at
- Perfect quality at roughly half the size of WAV.
- Archiving. A FLAC collection can be converted to any other format later without loss.
- Tags and artwork stored in the file.
- Open format, free to use with no licensing.
Where FLAC falls short
- Size compared with MP3. About 25–35 MB per song at CD quality, against 6–10 MB for a high-bitrate MP3.
- Device support. Modern phones, browsers and most music apps play FLAC, but many car stereos, older players and some smart speakers don’t.
- Streaming and mobile data. Lossless files use far more data.
FLAC and other formats
Keep FLAC as your master copy, and convert to MP3 for phones, cars and devices that don’t support it. Converting MP3 to FLAC is pointless: it makes a larger file without restoring any quality.