.FLAC file signature
A FLAC audio bitstream data file begins with the bytes 66 4C 61 43 (fLaC in ASCII) at the start of the file. The signature is the same whatever the file is named, which is why a renamed or extensionless FLAC file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 66 4C 61 43 | fLaC |
MIME type: audio/flac · usual extensions: .flac
How to check a file's signature
Without installing anything: drop the file on our detector. It reads the bytes in your browser and shows the hex dump alongside the verdict; nothing is uploaded.
macOS and Linux (Terminal):
xxd -l 32 file.flac
file file.flacWindows (PowerShell):
Format-Hex -Path file.flac -Count 32If the bytes do not match
A file named .flac whose first bytes are something else is not a FLAC file. The common explanations are a wrong or deliberately misleading extension, a download that saved an HTML error page instead of the file, or a container such as ZIP wrapping the real content. The detector reports what the bytes say; the FLAC guide explains what a genuine file should contain.