.GIF file signature
A GIF image data file begins with the bytes 47 49 46 38 39 61 (GIF89a 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 GIF file is still recognisable.
Known signatures
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 47 49 46 38 39 61 | GIF89a |
| 0 | 47 49 46 38 37 61The older version, without transparency or animation. | GIF87a |
MIME type: image/gif · usual extensions: .gif
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.gif
file file.gifWindows (PowerShell):
Format-Hex -Path file.gif -Count 32If the bytes do not match
A file named .gif whose first bytes are something else is not a GIF 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 GIF guide explains what a genuine file should contain.