FLAC stands for Free Lossless Audio Codec. Grossly oversimplified, FLAC is similar to MP3, but lossless. The FLAC project consists of:
- the stream format
- reference encoders and decoders in library form
- flac, a command-line program to encode and decode FLAC files
- metaflac, a command-line metadata editor for FLAC files
- input plugins for various music players
"Free" means that the specification of the stream format is fully open to the public to be used for any purpose (the FLAC project reserves the right to set the FLAC specification and certify compliance), and that neither the FLAC format nor any of the implemented encoding/decoding methods are covered by any known patent. It also means that all the source code is available under open-source licenses.
FLAC compiles on many platforms: most Unixes (Linux, *BSD, Solaris, OS X), Windows, BeOS, and OS/2. There are build systems for autoconf/automake, MSVC, Watcom C, and Project Builder.
See the features page, documentation page, or FLAC format page for more info, or the comparison page to see how FLAC compares with other lossless codecs.