FLAC (Free Lossless Audio Codec)
Every bit of your audio, preserved perfectly and compressed without a single detail lost.
| Full name | Free Lossless Audio Codec |
| Extension | .flac |
| MIME type | audio/flac |
| Developer | Josh Coalson; maintained by the Xiph.Org Foundation since 2003 |
| Released | 2001 (version 1.0 on July 20, 2001) |
| Type | Lossless audio compression |
| Bit depth support | 4 to 32 bits per sample |
| Channel support | 1 to 8 channels |
What is a FLAC file?
FLAC is a lossless audio format that compresses audio files without throwing away any data. When you decode a FLAC file, you get back the exact same audio that went in. It is free, open-source, and widely supported across music players, audio editors, and streaming services.
FLAC stores audio as pulse-code modulated (PCM) data, the same raw format used on CDs, but compressed so the file takes up less space. Unlike MP3 or AAC, FLAC does not approximate or discard audio information to save space. A FLAC file decoded by any compliant player will produce bit-for-bit identical output every time. Sample rates up to 1,048,575 Hz and bit depths up to 32 bits are supported, well beyond what human hearing can detect.
History
Josh Coalson started developing FLAC in 2000 and released version 0.5 on January 15, 2001, at which point the bitstream format was frozen for stability. Version 1.0 followed on July 20, 2001. On January 29, 2003, the Xiph.Org Foundation, also home to Ogg Vorbis and Ogg Theora, brought FLAC under its umbrella, where it has been maintained as a free and open standard ever since.
How it works
A FLAC file starts with the four-byte marker 'fLaC', followed by a mandatory STREAMINFO metadata block that describes the audio properties. Additional optional metadata blocks can store tags, album art, seek tables, and cue sheets. The actual audio data follows as a sequence of frames, each with a header, compressed samples, and a CRC16 checksum for error detection.
What it is used for
- Archiving a music collection at full quality before converting to smaller formats for playback
- Audio mastering and production where the original signal must be preserved across editing sessions
- Distributing high-resolution audio downloads from artists and labels who want buyers to receive exact studio quality
- Ripping CDs to a lossless format so nothing is lost if you later need a different format
How to open it
FLAC files open natively in players like VLC, foobar2000, Winamp, and most modern media apps on Android and Linux. On macOS and iOS, Apple Music supports FLAC since macOS Catalina (10.15) and iOS 11.
Pros and cons
Strengths
- Bit-perfect audio: decoding always reproduces the original signal exactly
- Typically achieves 40-60% size reduction compared to uncompressed WAV or AIFF
- Free and open-source with no patent encumbrance
- Supports metadata tags, album art, seek tables, and multi-channel audio up to 8 channels
Trade-offs
- Files are noticeably larger than lossy formats like MP3 or AAC at equivalent listening quality
- Not natively supported on older hardware players or some car stereos without firmware updates
- Overkill for casual listening where a 256 kbps AAC file is perceptually transparent to most ears
- Streaming services rarely offer FLAC because the bandwidth cost is high relative to perceived benefit
Convert FLAC files
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From FLAC
Curious how fast and how small? See our measured conversion benchmarks.
FLAC FAQ
Is FLAC really lossless, or does it lose some quality?
It is genuinely lossless. Decoding a FLAC file produces a bit-for-bit identical copy of the original PCM audio. No audio information is approximated or discarded during compression.
How much smaller is FLAC compared to WAV?
FLAC typically reduces file size by 40 to 60 percent compared to uncompressed WAV. A 50 MB WAV might compress to around 25-30 MB as FLAC, depending on the content.
Can I convert FLAC to MP3 without losing quality?
Converting FLAC to MP3 introduces lossy compression at the MP3 step, so the resulting MP3 will not be lossless. However, starting from FLAC guarantees you are encoding from the highest-quality source, which is better than re-encoding from another lossy file.
Does FLAC work on iPhone or Android?
Android has supported FLAC natively since Android 3.1. On iPhone, Apple Music added FLAC playback support in iOS 11, so modern iPhones play FLAC files without any third-party app.