FLAC
FLAC (Free Lossless Audio Codec) is an open audio format that compresses sound without throwing away any information. A FLAC file usually takes up around half to two thirds of the space of the raw original, yet decodes back to an exact copy. FLAC is popular for music archives and high-resolution audio. FLAC is rarely used as the audio track in streaming video.
Why it matters
FLAC preserves original audio perfectly while saving storage, which matters for music archives and master files. For video streaming it is usually the wrong delivery format, since files are much larger than AAC and device support is weaker, so it is converted.
How it works
- The encoder reads raw audio samples in short blocks.
- It predicts each sample from earlier ones and keeps only the small difference.
- Those differences are packed with an efficient code, without discarding anything.
- On playback, the decoder reverses the steps to rebuild the exact original audio.
FLAC vs AAC: which should I use?
Use FLAC for archiving or masters, where perfect quality matters, and AAC for streaming video, where file size and device support matter. FLAC is lossless but produces much larger files. AAC is lossy but sounds clear at modest bitrates and plays on nearly every device.
How much smaller is FLAC than WAV?
FLAC files are typically 50% to 70% of the original WAV size, depending on the music. Quiet or simple recordings compress more, while dense, noisy recordings compress less. In every case, the decoded audio is identical to the original, sample for sample.
Where it's used
Music streaming services and audio archives use FLAC for master-quality sound. Video platforms that receive FLAC inside uploads usually convert it to AAC for playback.
By the numbers
- FLAC version 1.0 was released on July 20, 2001. (Wikipedia: FLAC)
- FLAC is specified in RFC 9639, published in December 2024, which supports 1 to 8 channels and bit depths from 4 to 32 bits. (IETF RFC 9639)
