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FLAC
What is a FLAC file?
Lossless compression at about half the size of WAV. The archival choice for music.
What FLAC is
FLAC is a codec: the encoding itself rather than the box it travels in. It is used for archiving.
The extension is .flac, and the full name is Free Lossless Audio Codec. Both matter less than what the file can hold, which is what the rest of this page is about.
Where FLAC came from
Xiph.Org published it in 2001. The specification is RFC 9639.
Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.
The specification is public
Anyone can implement it without asking permission or paying a licence, which is why it turns up in so many programs and why files written twenty years ago still open.
Nothing is thrown away
FLAC stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.
Colour it can describe
Up to 32 bits per channel.
More than eight bits per channel is what stops a gradient from stepping when it is edited, which is why it matters in a working file and rarely in a finished one.
How many audio channels
Up to 8. Two covers stereo and is what almost everything is; more than two is surround, and it is the part most likely to be folded down when converting to a format that does not define it.
What it does to protect itself
FLAC carries a checksum, so a damaged file is detected rather than silently mis-read.
A checksum will not repair anything. It tells you the file is wrong, which is the difference between finding out now and finding out from whoever you sent it to.
What opens FLAC
Audacity, foobar2000 and VLC read it, and so do most programs of the same kind.
If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.
Opening it in a browser
Every current browser reads it.
That makes it a safe thing to put on a page or attach to a message without wondering what the other end has installed.
What it can carry besides the content
FLAC can hold document properties.
Whether any of it survives a conversion depends entirely on the target, and the honest answer is usually "some of it".
It is a working format
FLAC is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.
The facts, in one place
| Extension | .flac |
|---|---|
| Media type | audio/flac |
| Published by | Xiph.Org |
| First published | 2001 |
| Specification | RFC 9639 |