glTF (binary GLB) file signature
Magic number at the start of the file · glTF
A binary glTF (.glb) file starts with the ASCII magic glTF, then a 32-bit version (2) and total length. Text .gltf files are JSON and instead start with an opening brace.
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 67 6C 54 46 (the text glTF), it is a glTF (binary GLB) file.
Formats that use the 67 6C 54 46 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.gltf
- hexdump -C -n 16 example.gltf
- file example.gltf
Windows (PowerShell)
- Format-Hex -Path example.gltf -Count 16
Python
- open("example.gltf","rb").read(4).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the glTF (binary GLB) file signature?
glTF (binary GLB) files start with the hex bytes 67 6C 54 46 (glTF 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.gltf on Linux or macOS, or Format-Hex -Path example.gltf -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the glTF (binary GLB) signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine glTF (binary GLB) file has these exact bytes; a file with the wrong bytes is not really glTF (binary GLB), whatever its name says.