What Is FLAC?

What makes FLAC different

Most common audio formats fall into one of two categories: lossy (MP3, AAC — smaller files, some quality reduction) or uncompressed lossless (WAV, AIFF — full quality, very large files). FLAC sits in a third category that combines the benefits of both: it's compressed, but losslessly. The file is smaller than WAV. The audio is identical to the original.

This sounds too good to be true, but it's technically straightforward. Lossless compression doesn't discard data — it finds more efficient ways to represent the same data. The tradeoff is that lossless compression achieves less size reduction than lossy compression. FLAC gets you 40–60% smaller than WAV; MP3 gets you 90% smaller. You choose based on what you're willing to give up.

How FLAC compression works

FLAC uses a prediction algorithm. At its core, it works like this: for each audio sample, the encoder predicts what the value should be based on the previous few samples. It then stores the difference between the prediction and the actual value — called the residual. Residuals are typically much smaller numbers than the original sample values, so they can be stored in fewer bits.

When decoding, the same prediction runs again on the stored residuals, and the original audio is reconstructed perfectly. The key insight: as long as you can reproduce the prediction algorithm exactly, you can fully recover the original data.

FLAC offers compression levels from 0 to 8. Higher levels spend more encoding time to achieve slightly better compression ratios. All levels are lossless — the difference is only encoding speed and file size, not audio quality. The default level (5) is a good balance for most uses.

File sizes: FLAC vs WAV vs MP3

FLAC vs WAV: what actually differs

FLAC is not a better MP3

A common misconception: FLAC is a step above MP3 on some quality ladder. It isn't — they solve completely different problems. MP3 is lossy and optimised for small file size with acceptable quality. FLAC is lossless and optimised for perfect quality with reasonable file size.

They're not better and worse versions of the same thing. They're different tools for different jobs. Choosing between FLAC and MP3 is a question of what you're doing with the audio — not a question of which is "higher quality" in some abstract sense.

If you're distributing audio publicly — sharing, streaming, podcast delivery — MP3 or AAC is the right format. FLAC is far too large for casual distribution and the quality difference is inaudible to most listeners in most conditions anyway. If you're archiving, editing, or passing audio between producers — FLAC is the right format.

FLAC support in 2025

FLAC support has become nearly universal. Android has played FLAC natively since Android 3.1 (2011). macOS has supported FLAC natively since Big Sur (2020). Windows Media Player added FLAC support in Windows 10. VLC, foobar2000, and virtually all open-source audio players have supported it for years.

Apple Music now streams lossless audio (ALAC, which is Apple's lossless codec, very similar to FLAC). Tidal and Qobuz stream FLAC natively. Audiophile streaming is no longer a niche — it's a standard offering from major platforms.

The main exception: older iPods and iPhones before iOS 11 don't support FLAC — they use ALAC (Apple Lossless) instead. For the Apple ecosystem specifically, ALAC in an M4A container has historically been more reliable, though modern Apple devices handle FLAC without issues.

When to use FLAC

• Archiving your music collection:FLAC is the best format for long-term music storage. Full quality, reasonable size, rich metadata, and open standard — nothing proprietary to worry about.
• Storing recording projects:If you record music, archive the finished takes in FLAC before doing anything else. You'll have a lossless master to generate any distribution format later.
• Sharing audio with collaborators:Sending audio to a mix engineer or mastering engineer? FLAC gives them the full source quality at a manageable file size.
• Hi-fi listening:If you have a good DAC and headphones or speakers, FLAC lets you hear the recording without any lossy codec's fingerprint.

Converting with FLAC

Converting WAV to FLAC is lossless — you get a smaller file, identical audio. Converting FLAC to WAV is also lossless in the opposite direction. Neither involves any quality loss.

Converting FLAC to MP3 is a one-time, controlled quality reduction. You're applying lossy compression to a lossless source — the best possible starting point for that conversion.

Converting MP3 to FLAC doesn't improve quality. You get a lossless file that contains the same audio as the MP3. The lossy data that the MP3 encoder discarded is not recoverable — the FLAC wrapper can't reconstruct it.

Note: on this site, FLAC output is only available when converting from lossless source formats (WAV, AIFF, ALAC). Converting a lossy source to FLAC would produce a lossless wrapper around lossy audio — larger file, no quality benefit — so that option is not offered.