.flac File Extension

What kind of file is a .flac?

A .flac file is a native Free Lossless Audio Codec stream. It compresses PCM audio without changing any sample values when decoded, making it useful for music libraries, recordings, and archival masters. It can also store tags, cuesheets, seek points, and embedded cover artwork.¹

The registered MIME type is audio/flac. The older audio/x-flac MIME type remains common but is now a deprecated alias.¹ Native FLAC begins with the ASCII signature fLaC, or hexadecimal bytes 66 4C 61 43, followed by a required STREAMINFO block.¹

How do I open a .flac on my computer?

Current Chrome, Edge, Firefox, Opera, and Safari releases can play FLAC through an HTML audio element.² Desktop and mobile support can still vary for unusual sample rates, bit depths, or channel layouts.

• Windows, macOS, and Linux: VLC plays FLAC, while Audacity can play, edit, and export it.
• iPhone, iPad, and Android: current media apps commonly support FLAC, though the default app and supported stream properties vary by device.
• Command line: FFmpeg can inspect or convert FLAC. The reference flac tool can encode, decode, and test a file.³

Run flac --test recording.flac to validate a stream without writing decoded audio. When the file includes the optional STREAMINFO MD5 value, the tool also checks the decoded samples against it.³

Poly support for .flac

Poly recognizes .flac audio, extracts duration and available tags, and can use embedded artwork as a thumbnail. Files open in the audio player, where transcript matches can seek to the relevant moment.

Spoken audio is transcribed for full-text search, and audio similarity can find recordings that sound alike. The Poly agent can use the audio and its generated transcript. Instrumental music or unclear speech may produce little useful transcript text, while playback depends on the browser decoding the particular stream.

History of .flac

Josh Coalson began FLAC in 2000, and the bitstream was considered frozen with FLAC 1.0 in July 2001.¹ Xiph.Org later maintained the specification and reference implementation.

In December 2024, RFC 9639 formally documented FLAC as an IETF Proposed Standard and registered audio/flac. The RFC largely standardized the established format while adding 32-bit audio support and several interoperability restrictions.⁴

Working with .flac and alternatives

Every valid FLAC compression level reconstructs the same PCM samples. Higher levels spend more encoding time searching for a smaller representation; they do not improve sound quality.³

Decoding FLAC to PCM WAV can preserve the audio samples when the bit depth and channel layout match, but FLAC-specific tags, pictures, and cuesheets may not transfer. Encoding FLAC to a lossy codec discards information, so keep the .flac original if you may need another export later.

The STREAMINFO MD5 can detect accidental changes in decoded audio, but it is not a signature of authorship. Review tags and embedded artwork before sharing a private recording.