.H5 file signature
A Hierarchical Data Format v5 file begins with the bytes 89 48 44 46 0D 0A 1A 0A (.HDF.... 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 H5 file is still recognisable.
Signature
| Offset | Hex | ASCII |
|---|---|---|
| 0 | 89 48 44 46 0D 0A 1A 0AMay appear at offset 0, 512, 1024, 2048 and so on if a user block precedes it. | .HDF.... |
MIME type: application/x-hdf · usual extensions: .h5, .hdf5
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.h5
file file.h5Windows (PowerShell):
Format-Hex -Path file.h5 -Count 32If the bytes do not match
A file named .h5 whose first bytes are something else is not a H5 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 H5 guide explains what a genuine file should contain.