This document defines the Free Lossless Audio Codec (FLAC) format. FLAC is designed to reduce the amount of computer storage space needed to store digital audio signals without needing to remove information in doing so (i.e. lossless). FLAC is free in the sense that its specification is open, its reference implementation is open- source and it is not encumbered by any known patent. Compared to other lossless (audio) coding formats, FLAC is a format with low complexity and can be coded to and from with little computing resources. Decoding of FLAC has seen many independent implementations on many different platforms, and both encoding and decoding can be implemented without needing floating-point arithmetic.