GGUF (local LLM) file signature
Magic number at the start of the file · GGUF
A GGUF model file, the format llama.cpp and Ollama use to run large language models locally, starts with the ASCII magic GGUF, followed by a version and a key-value metadata block.
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 47 47 55 46 (the text GGUF), it is a GGUF (local LLM) file.
Formats that use the 47 47 55 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.gguf
- hexdump -C -n 16 example.gguf
- file example.gguf
Windows (PowerShell)
- Format-Hex -Path example.gguf -Count 16
Python
- open("example.gguf","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 GGUF (local LLM) file signature?
GGUF (local LLM) files start with the hex bytes 47 47 55 46 (GGUF 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.gguf on Linux or macOS, or Format-Hex -Path example.gguf -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the GGUF (local LLM) signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine GGUF (local LLM) file has these exact bytes; a file with the wrong bytes is not really GGUF (local LLM), whatever its name says.