.MSI file signature
A Microsoft Installer file begins with the bytes D0 CF 11 E0 A1 B1 1A E1 at the start of the file. The signature is the same whatever the file is named, which is why a renamed or extensionless MSI file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | D0 CF 11 E0 A1 B1 1A E1OLE2 compound document, the same header as .doc. |
MIME type: application/x-msi · usual extensions: .msi
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.msi
file file.msiWindows (PowerShell):
Format-Hex -Path file.msi -Count 32If the bytes do not match
A file named .msi whose first bytes are something else is not a MSI 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 MSI guide explains what a genuine file should contain.