bzip2 file signature
Magic number at the start of the file · BZh
bzip2 compressed data begins with the ASCII magic BZh, followed by a single ASCII digit 1 to 9 giving the block size in hundreds of kilobytes. A .tar.bz2 is a tar archive inside a bzip2 stream.
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 42 5A 68 (the text BZh), it is a bzip2 file.
Formats that use the 42 5A 68 signature
These file types in our database carry this signature:
It is also seen in: BZ2, TBZ2.
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.tar
- hexdump -C -n 16 example.tar
- file example.tar
Windows (PowerShell)
- Format-Hex -Path example.tar -Count 16
Python
- open("example.tar","rb").read(3).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the bzip2 file signature?
bzip2 files start with the hex bytes 42 5A 68 (BZh 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.tar on Linux or macOS, or Format-Hex -Path example.tar -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the bzip2 signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine bzip2 file has these exact bytes; a file with the wrong bytes is not really bzip2, whatever its name says.