Apache Avro file signature
Magic number at the start of the file · Obj.
An Avro object container file starts with the ASCII letters Obj followed by the version byte 0x01, then the embedded JSON schema and blocks of binary records.
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 4F 62 6A 01 (the text Obj.), it is a Apache Avro file.
Formats that use the 4F 62 6A 01 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.avro
- hexdump -C -n 16 example.avro
- file example.avro
Windows (PowerShell)
- Format-Hex -Path example.avro -Count 16
Python
- open("example.avro","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 Apache Avro file signature?
Apache Avro files start with the hex bytes 4F 62 6A 01 (Obj. 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.avro on Linux or macOS, or Format-Hex -Path example.avro -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the Apache Avro signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine Apache Avro file has these exact bytes; a file with the wrong bytes is not really Apache Avro, whatever its name says.