A FLAC file is an audio file compressed in the Free Lossless Audio Codec (FLAC) format, which is an open source lossless audio compression format. It is similar to an .MP3 file, but is compressed without any loss in quality or loss of any original audio data.

FLAC reduces the size of digital audio approximately 60 percent and is a widely supported format across the most popular platforms. It is open source and developed by the Xiph.Org Foundation. A FLAC Fingerprint file, which contains the filename and checksum information for a FLAC file, may be generated along with the FLAC file. This file is typically named "ffp.txt" and can be created using the following command: "metaflac --show-md5sum flac_file_names > ffp.txt". For additional information about the FLAC format visit the FLAC website.