VHDX (Hyper-V disk) file signature
Magic number at the start of the file · vhdxfile
The modern Hyper-V virtual disk begins with the ASCII magic vhdxfile, followed by the headers and log that make VHDX resilient to power loss.
What this magic number means
A magic number is a short, fixed run of bytes at a known position that tells a program what a file really is, no matter what the filename says. If a file starts with the bytes 76 68 64 78 66 69 6C 65 (the text vhdxfile), it is a VHDX (Hyper-V disk) file.
Formats that use the 76 68 64 78 signature
These file types in our database carry this signature:
How to check a file's signature
You can read the first bytes of any file yourself. The magic bytes are shown in hex, the same way this page lists them.
Linux & macOS
- xxd -l 16 example.vhdx
- hexdump -C -n 16 example.vhdx
- file example.vhdx
Windows (PowerShell)
- Format-Hex -Path example.vhdx -Count 16
Python
- open("example.vhdx","rb").read(8).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the VHDX (Hyper-V disk) file signature?
VHDX (Hyper-V disk) files start with the hex bytes 76 68 64 78 66 69 6C 65 (vhdxfile in ASCII). This magic number identifies the format regardless of the file's name or extension.
How do I check a file's magic number?
Open the file in a hex editor, or run a command such as xxd -l 16 example.vhdx on Linux or macOS, or Format-Hex -Path example.vhdx -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the VHDX (Hyper-V disk) signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine VHDX (Hyper-V disk) file has these exact bytes; a file with the wrong bytes is not really VHDX (Hyper-V disk), whatever its name says.