.HLP file signature
A MS Windows help file begins with the bytes 3F 5F 03 00 (?_ 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 HLP file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 3F 5F 03 00 | ?_ |
MIME type: application/winhlp · usual extensions: .hlp
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.hlp
file file.hlpWindows (PowerShell):
Format-Hex -Path file.hlp -Count 32If the bytes do not match
A file named .hlp whose first bytes are something else is not a HLP 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 HLP guide explains what a genuine file should contain.